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Stereo Analyst ® User's Guide

1. Feature Stereo i Feature Feature Class File Analyst Bitmap FCODE Type Name fcl Name Township or range line town line US Township 23 bmp 4000 Polyline Line Township or range line location location doubt Location 24 bmp 4001 Polyline doubtful Doubtful Section line section line US Section LIne 25 bmp 4002 Polyline Other Land Surveys Township or range line other t line Other Town Line 28 bmp 4003 Polyline Section line other sec line Other Sect Line 29 bmp 4005 Polyline Land grant or mining claim mining claim Mining Claim 30 bmp 4006 Polyline monument Fence line fence line Fence Line 31 bmp 4007 Polyline Surface Features Levee levee Levee 32 bmp 5000 Polyline Sand or mud area dunes or shifting sand Sand 33 bmp 5001 Polygon sand Intricate surface area int surface Intricate Surface 34 bmp 5002 Polygon Gravel beach or glacial moraine grav beach Gravel Beach 35 bmp 5003 Polygon Tailings pond tail pond Tailings Pond 36 bmp 5004 Polygon Mines and Caves Quarry or open pit maine quarry Quarry 37 bmp 6000 Polygon Gravel sand clay or borrow pit gravel pit Gravel Pit 39 bmp 6001 Polygon Mine tunnel or cave entrance mine tunnel Mine Tunnel 40 bmp 6002 Polyline Prospect mine shaft prospect Prospect 41 bmp 6003 Polygon Mine dump mine dump Mine Dump 42 bmp 6004 Polygon Tailings tailings Tailings 43 bmp 6005 Polygon Vegetation Woods w
2. Parallel Click this icon to create features of parallel lines s This tool is useful to digitize roads Streaming Click this icon to enable stream mode digitizing L This allows for the continuous collection of a polyline or polygon feature without the continuous selection of vertices Polygon Click this icon to complete a building or other ol Close square or rectangular feature after collecting only three corners Reshape Click this icon to reshape an existing feature You r1 can then click on any one of the vertices that makes up the feature to adjust its position Polyline Click this icon to add vertices to the end of an amp Extend existing feature Remove Click this icon to remove segments from existing Segments line features Add Click this icon to add an element to an existing amp l Element feature Select Click this icon to select a specific element of a m Element feature but not the entire feature 3D Extend Click this icon to extend the corners of a feature to the ground Next you can learn how 3D geographic imaging is used in various GIS applications Next 9 Stereo Analyst Next 10 3D Imaging E Introduction Stereo Analyst The collection of geographic data is of primary importance for the creation and maintenance of a GIS If the data and information contained within a GIS are inaccurate or outdated the resulting analysis performed on the data do not reflect true
3. bef AAA be 08s Pe esce Ram om Save the Stereo A DSM can be saved as a stereo anaglyph image that can be used in Modeltoan Image the field or laboratory to conduct airphoto interpretation Using hardcopy anaglyph stereo prints is useful for interpreting height and File geographic information while in the field Hardcopy anaglyph stereo prints can also be shared with others to convey geographic information Stereo Analyst Save the Stereo Model to an Image File 101 B Open the New DSM Stereo Analyst Saving a DSM records and captures the image contained within the Main View of the Digital Stereoscope Workspace If the Stereo Mode is Quad Buffered Stereo the resulting image is saved as Color Anaglyph Stereo Click File menu of the Digital Stereoscope Workspace select View to Image The View to Image dialog opens Navigate to a directory in which you have write permission Click in the File name field and type the name la merge then press Enter on your keyboard The img extension is added automatically Click OK in the View to Image dialog You can now open the new DSM in the Digital Stereoscope Workspace Click the Clear View icon amp Click the Open icon i Navigate to the directory in which you saved the DSM la_merge img Select the image la_merge img then click OK in the Select Layer To Open dialog Click OK in the dialog prompting you to create pyramid layers siete The wage
4. 64 Profile View of a Stereopair sasaaa aaa a a 65 Parallax Comparison Between Points 0 0 0 cee a ee es 65 Parallax Reflects Change in Elevation e o 66 Y parallax ExistS s s o mor w e mai a a i e e rho oho honos n 67 Y parallax Does Not EXiSt 0 es 67 DSM without Sensor Model Information 000 cee a eee ees 68 DSM with Sensor Model Information 2 a a 69 Space Intersection aoaaa aaa a a a 71 Stereo Model in Stereo and Mono e 72 X Parallax p essa arwa ee d ud e ke Paa a EEG vx 104 LE e card om ioni a Rak er i ara o rg ate How SR A a rca Goan hd Da E d 104 Cursor Floating Above a Feature o a eres 107 Cursor Floating Below a Feature a 108 Cursor Resting On a Feature eee 109 Epipolar Geometry and the Coplanarity Condition sn 264 Stereo Analyst ix Stereo Analyst x List of Tables Table 1 Stereo Analyst Digital Stereoscope Workspace Menus 0 o eee 5 Table 2 Stereo Analyst Toolbar a a sh sh soy ah aon sons 6 Table 3 Stereo Analyst Feature Toolbar eee lees ns 8 Table 4 Scanning Resolutions ele heh hon ns 39 Table 5 Interior Orientation Parameters for Frame 1 la left img 123 Table 6 Exterior Orientation Parameters for Frame 1 la_left img 123 Table 7 Interior Orientation Parameters for Frame 2 la right im
5. llle 42 Interior Orientation ls 44 Principal Point and Focal Length lt 44 Fiducial Marks leen 45 Lens Distortion oes 5s oo ono hl XR 46 Exterior Orientation rn 47 The Collinearity Equation l lere 49 Digital Mapping Solutions 51 Space Resection 1 ooo concen 51 Space Forward Intersection o ooo oooooo oo 52 Bundle Block Adjustment o o ooooooooo oo 53 Least Squares Adjustment o ooo ooo ooo 56 Automatic Gross Error Detection 59 MOX ee ee ee ee 59 Stereo Viewing and 3D Feature Collection 61 Introduction ee rrr 61 Principles of Stereo Viewing 61 Stereoscopic Viewing seen 61 How it WOrIKS 3 pa ius Yu Reg a ROUX m a 62 Stereo Analyst Table of Contents iv Stereo Models and Parallax 64 X parallaxX 4529 mme ra Ra x RR EEG S 64 Ysparallax uae oon ca Mies Red bees 66 Scaling Translation and Rotation 67 3D Floating Cursor and Feature Collection 69 3D Information from Stereo Models 70 Next pass asis ud ene ww E aaa e e od 72 Tour GUIGES xs cia aca a ee wT Creating a Nonoriented DSM 0 75 Introduction llle 75 Getting Started nnn 76 Launch Stereo Analyst l l 76 Adjust the Digital Stereo
6. 7 Click to digitize the first vertex on the right side of the sidewalk 8 Move your mouse back to the left hand side of the sidewalk and click to collect the next point 9 Adjust the cursor elevation as necessary this sidewalk has a good deal of slope and continue to collect the sidewalk to the end 10 Double click to stop digitizing the sidewalk 11 Click outside of the sidewalk to deselect it The following picture illustrates the termination of the sidewalk zoomed in You can see the change in elevation reflected here as exaggerated x parallax Remember if you make mistakes there are several Stereo Analyst tools to help you correct them such as the Polyline Extend tool and the Reshape tool See the On Line Help for more information Stereo Analyst Collect Roads and Related Features 200 Zoom Out to See the Entire Feature 1 Use your mouse to zoom out so that the entire sidewalk is visible in the Main View You need to adjust x parallax to see specific portions of the sidewalk in stereo however the feature has been collected appropriately A 2 Click the Zoom to Full Extent icon Es E 2j Collect a Road Again locate the appropriate feature using the Position tool Open the Position Tool 1 Click the Position tool icon in the toolbar of the Digital Stereoscope Workspace The Digital Stereoscope Workspace adjusts to accommodate the Position tool First you are going to
7. 101 ileftimagenamei id stereo analyst stereo analyst tstretchimagei ili irightnumtotalbandsi 111 splaybandsi ili analyst stereo a n 254 imgi ImageHistory irightimagenamei nalyst ImageName id stereo analyst stereo Stereo Analyst Feature Project and Project File E Stereo Analyst Feature Classes General Information Stereo Analyst analyst iFALSEi analyst data wes iblockfi Er p data western western blockl blki iTRU LayerArgs ilayername id stereo stereo analyst tern western blockl blk ilayertype iblocki data wes 111 ilef ileftnumdisplaybandsi ili 101 id ster data wes irightinvertcolorsi 101 irightnu id ster data wes lenamei id stereo analyst stereo analyst tern western blockl blk ileftstretchimage tinvertcolors 101 ileftnumtotalbandsi ili ileftimagenamei eo analyst stereo analyst tern 251 imgi irightstretchimagei ili irightnumtotalbandsi 111 mdisplaybandsi ili 101 irightimagenamei eo analyst stereo analyst tern 252 imgi StereoPairs i251 img amp 252 img1 analyst data western western block2 blki analyst data wes iTRUEL iFALSEi ImageName id stereo analyst stereo iTRUE 1TRUE1 LayerArgs ilayername id stereo stereo analyst tern western_block2 b1k1 ilayertype iblocki iblockfi data wes 111 ilef ileftnum id ster data wes irightinvertcolors
8. NOTE Again several of the vertices in the Active image are occluded by incidental artifacts in the image You must simply make your best guess as to where these vertices lie 3 Click the Align Model To Image button on the Model Options dialog The Align Model to Image function attempts to automatically align the selected vertices of the model to the placement you assigned on the Active Image It does this by approximating the FOV and Perspective in the image The greater the number of vertices that are selected the better the estimated alignment To return the model and image to the original FOV and perspective click the return to default view button 5 on the Texel Mapper toolbar un This is an inexact science and you may need to readjust the vertices and realign the model to the image a few times before you get a suitable alignment Texturizing the Model 228 Repeat step 2 and step 3 until the model is relatively well aligned with the feature in the image For minor adjustments rotate and zoom the model manually When you have a good alignment hold the middle button and magnify the model so that it still lines up with the corners but the model is slightly larger than the feature in the image This allows you some leeway when you are fine tuning the texture The vertices align but are slightly outside of the actual corners Extract and Map the Texture Stereo Analyst Extracting and mapping textures
9. Terrain Following Cursor The terrain following cursor is one of the utilities in Stereo Analyst that you can toggle on and off When the utility is on there is no need to manually adjust the height of the cursor to meet the feature of interest via the mouse In this mode the 3D floating cursor identifies the position of a feature appearing in the stereopair and automatically adjusts the height of the 3D floating cursor so that it always rests on top of the point of interest You can access it via the Utility menu or via the right mouse button Take the First The first measurement you are going to take is the length of a Measurement sidewalk Enter the 3D Coordinates 1 In the X field of the Position tool type 477759 50 2 In the Y field of the Position tool type 4761557 36 3 In the Z field of the Position tool type 251 99 Digitize the Polyline Stereo Analyst drives to the 3D coordinate position you specify 1 Position your cursor at the intersection of the crosshair and zoom into the area by pressing down the mouse wheel or middle mouse button and moving the mouse away from you NOTE After zooming in the point you entered in the Position tool may not be under the crosshair You may need to re enter the coordinates to see the exact location under the crosshair Digitize this sidewalk This particular sidewalk has a good deal of slope to it Before you begin measuring zoom out to get a full picture of the si
10. ikia SO Foot 3700 Coles x F Becta 2 Click the Files of type dropdown list and select IMAGINE Image 3 Navigate to the directory in which you saved the LA data then select the file named la left img 4 Click OK in the Select Layer To Open dialog NOTE If you have not computed pyramid layers for the image yet you are prompted to do so The file of Los Angeles California la left img displays in the Digital Stereoscope Workspace NOTE The screen captures provided in this tour guide were generated in the Color Anaglyph Stereo mode If you are running Stereo Analyst with the Quad Buffered Stereo configuration your images display in true color Stereo Analyst Open the Left Image 115 ui name of the image displays in the title bar of the Workspace If the image does not have projection information row and column information displays here E Add a Second Now you can add a second image so that you can view in stereo Image 1 From the File menu of the Digital Stereoscope Workspace select Open gt Add a Second Image for Stereo 2 In the Select Layer To Open dialog navigate to the directory where you saved the LA data and select the image la right img 3 Click OK in the Select Layer To Open dialog The images display in the Digital Stereoscope Workspace Stereo Analyst Add a Second Image 116 B Open the Create Stereo Model Dialog Stereo Analyst Left imag Right image Now that you have
11. 113 H Load the LA Data m Open the Left Image Stereo Analyst If you have already loaded the LA data set proceed to the next section Open the Left Image The data you are going to use for this tour guide is not located in the examples directory Rather it is included on a data CD that comes with the Stereo Analyst installation packet To load this data follow the instructions below Insert the Stereo Analyst data CD into the CD ROM drive Open Windows Explorer Select the files la_left img and la_right img and copy them to a directory on your local drive where you have write permission Ensure that the files are not read only by right clicking to select Properties then making sure that the Read only Attribute is not checked You are now ready to start the exercise As in the previous tour guide you must first open two mono images with which to create the DSM Click the Open icon x on the toolbar of the empty Digital Stereoscope Workspace The Select Layer To Open dialog opens Here you select the type of file you want to open in the Digital Stereoscope Workspace Open the Left Image 114 Select Layer To Open il Select the file la_left img Fe Opis tulo the left image of the DSM Lack in Ta i pem e This is the first image you ji pimp use to create the IMAGINE LPS Project Manager block file Select IMAGINE Image from the dropdown list Fiet of poa MAGNE braga il
12. Fieri ei pp BADHE Detrol mie Block Fin bd 166 Fiet 16 Subaesciones D Matera T 3504 Eute Free 2 Navigate to a directory in which you have write permission 3 Click in the File name field and type the name la create then press Enter on your keyboard The blk extension block file is automatically appended Stereo Analyst Open the Create Stereo Model Dialog Enter Projection Information Click OK in the Block filename dialog to accept the name for the block file The Create Stereo Model dialog is updated with the information To change the projection information you access another series of dialogs In the Create Stereo Model dialog click the Projection icon amp The Projection Chooser dialog opens In the Custom tab of the Projection Chooser dialog click the Projection Type dropdown list and choose UTM Click the Spheroid Name dropdown list and choose GRS 1980 Click the Datum Name dropdown list and choose NAD83 Use the arrows or type the value 11 in the UTM Zone field Confirm that the NORTH or SOUTH window displays North When you are finished the Projection Chooser looks like the following Udited Projects Chosser Stereo Analyst hanced Lion Progcion Type UT haced Nama Datura Hara UTH Zora HOATH e SMITH Mon Hace Use the ni dropdown Hash lists to make projection selections For more information about projections see the ERDAS IMAGINE On Line Help
13. Now that the texture has been applied to the roof you need to orient the tiles so that the lines in the tiled texture mimic those found on the actual building Enter the Tile Options mode by clicking the Tile Options icon zs on the Texel Mapper toolbar The Tile Options dialog displays Select the roof face that borders the front of the building Adjust the Rotate thumbwheel until the tiled texture lines run perpendicular to the roofline Before orientation After orientation Continue to select rotate and move all of the roof faces of the model until you have them all oriented to your satisfaction Look for untexturized faces and map blank wall textures to them Save the model by selecting File gt Save As gt Multigen OpenFlight Database and entering texel tour complete flt in the filename textbox You have a fully textured model of a building ready for inclusion in any 3D application Tiling a Texture 237 Stereo Analyst Tiling a Texture 238 Reference Material Stereo Analyst 239 Stereo Analyst 240 Feature Projects and Classes is Introduction This chapter provides information regarding the Stereo Analyst feature project and feature classes E Stereo Analyst A Stereo Analyst feature project is a mechanism for managing and F re Prol organizing all of the information associated with a digital mapping eature oJect project created in Stereo Analyst A feature project is a directory that
14. and Project File contains the following items e an ESRI 3D Shapefile shp for each user selected feature class e a backup ESRI 3D Shapefile file backup shp for each 3D Shapefile and e a feature class file fcl for each user selected feature class A feature class file contains detailed information associated with a feature class such as color display attributes and feature attributes The name of the feature class file corresponds to the name of the 3D Shapefile See Default Stereo Analyst Feature Classes for important information regarding maintenance of original fcl files distributed with Stereo Analyst a database dBase file dbf for each 3D Shapefile The dBase file contains all of the attribute table information associated with a 3D Shapefile e an index shx file for each 3D Shapefile The index file allows direct access to records in the main 3D Shapefile e a projection file prj for each 3D Shapefile The projection file contains all of the projection and unit information associated with a 3D Shapefile e an RDX file for each 3D Shapefile and e a Feature Project file fpj Stereo Analyst Stereo Analyst Feature Project and Project Stereo Analyst The feature project file is an ASCII file containing references to images feature classes etc The name of the feature project file corresponds to the name of the feature project directory A Stereo Analyst featur
15. m m4 mj M m mz My m5 M32 M33 The rotation matrix is derived by applying a sequential rotation of Omega about the x axis Phi about the y axis and Kappa about the Z axis The following section defines the relationship between the camera sensor the image and the ground Most photogrammetric tools utilize the following formulas in one form or another NOTE Stereo Analyst uses a form of the collinearity equation to continuously determine the 3D position of the floating cursor With reference to Figure 20 an image vector a can be defined as the vector from the exposure station O to the image point p A ground space or object space vector A can be defined as the vector from the exposure station O to the ground point P The image vector and ground vector are collinear inferring that a line extending from the exposure station to the image point and to the ground is linear The image vector and ground vector are only collinear if one is a scalar multiple of the other Therefore the following statement can be made a kA where k is a scalar multiple The image and ground vectors must be within the same coordinate system Therefore image vector a is comprised of the following components Exterior Orientation 49 Stereo Analyst XX Br Yo f where xo and yo represent the image coordinates of the principal point Similarly the ground vector can be formulated as follows X X A Y Y Z Zo In ord
16. Click OK in the Projection Chooser dialog to transfer the information to the Create Stereo Model dialog Confirm that the Map X Y Units are set to Meters Confirm that the Cartesian Units are set to Meters Open the Create Stereo Model Dialog 119 Stereo Analyst 10 11 12 13 Enter the value 3925 in the Average Height in meters field then press Enter on your keyboard The average height is also referred to as the average flying height The average height is the average elevation of the aircraft above the ground as it captured the images used to create the DSM Confirm that the Angular Units are set to Degrees Angular units are the units used to define the orientation angles Omega o Phi o and Kappa x Confirm that the Rotation Order is set to Omega Phi Kappa The angular or rotational elements associated with a sensor model Omega Phi and Kappa describe the relationship between the ground coordinate system X Y Z and the image coordinate system Different conventions are used to define the order and direction of the three rotation angles ISPRS recommends the use of the Omega Phi and Kappa convention or order In this case Omega is a positive rotation around the X axis Phi is a positive rotation about the Y axis and Kappa is a positive rotation around the Z axis In this system X is the primary axis Confirm that the Photo Direction is set to Z Axis The Z axis is selected when you us
17. Internal Geometry T gu Center y ZA Fiducial mark Focal tengas o Image plane X O The internal geometry of a camera is defined by specifying the following variables e principal point e focal length e fiducial marks e lens distortion The principal point is mathematically defined as the intersection of the perpendicular line through the perspective center of the image plane The length from the principal point to the perspective center is called the focal length Wang 1990 The image plane is commonly referred to as the focal plane For wide angle aerial cameras the focal length is approximately 152 mm or 6 inches For some digital cameras the focal length is 28 mm Prior to conducting photogrammetric projects the focal length of a metric camera is accurately determined or calibrated in a laboratory environment Interior Orientation 44 The optical definition of principal point is the image position where the optical axis intersects the image plane In the laboratory this is calibrated in two forms principal point of autocollimation and principal point of symmetry which can be seen from the camera calibration report Most applications prefer to use the principal point of symmetry since it can best compensate for any lens distortion Fiducial Marks As stated previously one of the steps associated with calculating interior orientation involves determining the image position of the
18. LPS Project Manager Point Measurement Tool Interface ana sl Ci 62750575 amp uZR WI T rui s i Florence lus ues e dogs er m n D ipina DAR at are L we Q ra 4t wx Ae Pane Vat Vis gen Mes menge NI I Aru j le rs o ww a iani Stereo Analyst Principles of Photogrammetry 33 Types of Photographs and Images Stereo Analyst The Leica Photogrammetry Suite Project Manager is capable of automating photogrammetric tasks using many different types of photographs and images Photogrammetry can be used to measure and interpret information from hardcopy photographs or images Sometimes the process of measuring information from photography and satellite imagery is considered metric photogrammetry Interpreting information from photography and imagery is considered interpretative photogrammetry such as identifying and discriminating between various tree types Wolf 1983 The types of photographs and images that can be processed include aerial terrestrial close range and oblique Aerial or vertical near vertical photographs and images are taken from a high vantage point above the surface of the Earth The camera axis of aerial or vertical photography is commonly directed vertically or near vertically down Aerial photographs and images are commonly used for topographic and planimetric mapping projects and are commonly captured from an aircraft or satellite Figure 9 illustrates a
19. Least squares condition 57 Left Buffer icon 8 Lens distortion 46 283 Line of sight 283 Line segment 283 Linear interpolation 283 Lithological 283 Lock icon 8 LOS 283 M Map coordinate system 283 Measure features 147 Metric photogrammetry 34 283 Model space coordinate system 283 Mono 283 Mosaicking 16 17 24 283 Multiple points 283 N Nadir 283 Nearest neighbor 265 283 New icon 6 Stereo Analyst Nonoriented DSM 75 stereopair 283 Nonorthogonality 46 283 O Object space coordinate system 283 Oblique photographs 34 284 Observation equations 55 Off nadir 284 Omega 43 49 275 284 Open Workspace icon 6 OpenGL 68 284 Orient the DSM 88 Orientation 49 matrix 284 Oriented stereopair 284 Orthogonal icon 8 Orthorectify 284 Outer parameter first 266 Outer parameter second 266 Output image file first 265 image file second 266 image number first 265 image number second 266 Overlay 284 Overview viewer 284 P Paging 284 Parallactic angle 284 Parallax 284 Parallel icon 9 Paste icon 8 Perspective center 41 285 Phi 43 49 275 285 Photogrammetric configuration 54 quality sensors 285 scanners 37 Photogrammetry 31 285 Photographic base 88 Pixel 285 Pixel coordinate system 40 45 Plane table photogrammetry 32 Planimetric information 32 Point 285 Polygon 285 Polygon Close icon 9 Polyline 285 Polyline Extend icon 9 Position Tool icon 7 Index 293 Principal point 41 44
20. The condition that specifies that the exposure station ground point and its corresponding image point location must all lie along a straight line Computer aided design CAD Computer application used for design and GPS survey Control point extension This technique requires the manual measurement of ground points on photos of overlapping areas The ground coordinates associated with the GCPs are then determined by using photogrammetric techniques of analog or analytical stereo plotters Coordinate system A method for expressing location In 2D coordinate systems locations are expressed by a column and row also called X and Y In a 3D coordinate system the elevation value is added called Z Coplanarity condition The coplanarity condition is used to calculate relative orientation It uses an iterative least squares adjustment to estimate five parameters By B Omega o Phi o and Kappa x The parameters explain the difference in position and rotation between the two images making up the stereopair Correlate Matching regions of separate images for the purposes of tie point or GCP collection as well as elevation extraction Datum Defines the height of the camera above sea level Degrees of freedom Also known as redundancy The number of unknowns is subtracted from the number of knowns The resulting number is the redundancy or degree of freedom in a solution Delta Difference usually in elevation slope or
21. X Parallax Example 1 Example 2 As illustrated in Example 2 both the road and the building can be clearly interpreted in 3D The optimum amount of x parallax should provide a clear 3D stereo view throughout the area of interest Once the ideal x parallax has been set you should not need to continually adjust x parallax within a localized geographic area of interest An exception to the rule is an area where a drastic change in elevation exists like an area of a downtown environment containing both a flat road and a 60 story building In this case you have to adjust the zoom level and the x parallax to effectively perceive 3D for the tall buildings Y parallax is a phenomenon that causes discomfort while viewing a DSM The following illustration contains Y parallax Figure 38 Y Parallax Example 1 Example 2 Adjusting Y Parallax 104 o Cursor Height Adjustment Stereo Analyst Two photographs comprising a DSM have been acquired at different positions and orientations that is different angles The difference in position and orientation can be perceived when the overlapping portions of two images are superimposed Since the two images were exposed at different orientations and positions the images will never perfectly align on top of one another In Stereo Analyst you must minimize the amount of y parallax to obtain an accurate and clear 3D DSM By adjusting y parallax you are accounting for the difference in or
22. adjusts the stereopair in the view accordingly Within a short distance you notice that the x parallax is not optimal In order to get an accurate measurement you need to adjust the x parallax and cursor elevation again Take 3D Measurements 156 f J 1 T n gt rm at d i As you digitize here check the monoscopic views to see that the cursor is on the same feature in both of the images 8 Adjust the x parallax and cursor elevation as necessary and continue digitizing the sidewalk NOTE The digitizing line seems to disappear while you adjust x parallax It reappears as you continue collecting vertices 9 Double click to stop digitizing the sidewalk Evaluate Results Once you stop digitizing the results of the measurements are displayed in the 3D Measure tool JD Means Tool Tig Eb RE AO Peddie 1 Leng 173 571 mede E Z demos 90143 euh Z DEVA pie P1 TITEL AA TL BUD ues AT Pi AFA AO 471558 001 eis 252 EME meter Deka E 00007 mere Seas a GOO 138337 depot PANA AA 440751555 BL P ren ANG A Deka E 00006 ene ego UCTE Ars 103 2325 degeret PAL ATITET CHIPS 410461555 4 ete 2 unu E Length is listed first Now that you have finished digitizing the polyline you can evaluate the 3D measurements NOTE The measurements of the polyline you digitized may differ from those digitized in this tour guide 1 Use the scroll bar to see the first line displayed in the 3D Measure tool text fiel
23. especially textures from perspective distorted images is an inexact science It involves trail and error so you may have to repeat these steps several times to achieve a satisfactory result Also your results may differ slightly from those shown in this tour Click the Extract Texture button on the Model Options dialog The portion of the image that underlies the selected faces on the model is extracted and creates a new Active Image called Extract 0 This image may appear slightly warped but this warping can be minimized in the mapping process If you are dissatisfied with the extracted texture for any reason simply select karolinerplatz right from the Active Image list and repeat the preceding steps in Align the Model Once you have extracted an image that shows all of the vertices and appears relatively unwarped return to Affine Map Options mode by clicking the Affine Map button m Drag the vertices so that they accurately rest on the corresponding building corners in the image As you move the vertices the texture on the model warps and stretches Texturizing the Model 229 4 Fine tune the position of each vertex to eliminate the worst of the warping and stretching Also watch to make sure that features that continue around corners match up Drag the vertices onto the corresponding points in the Extracted Image Adjust vertices to minimize warping and stretching Make sure features match acr
24. i01 irightnu id ster data wes lenamei id stereo analyst stereo analyst tern western block2 blk ileftstretchimage tinvertcolors 101 ileftnumtotalbandsi ili displaybands ili 101 ileftimagenamei eo analyst stereo analyst tern 253 imgi irightstretchimagei ili irightnumtotalbandsi 111 mdisplaybandsi ili 101 irightimagenamei eo analyst stereo analyst tern 254 imgi StereoPairs 1253 img amp 254 img1 TRUE 1TRUE The default Stereo Analyst feature classes are based on 1 24 000 USGS topographic map symbols used for the photogrammetric compilation of topographic and planimetric maps by the USGS The default feature classes serve as templates used for collecting 3D features in Stereo Analyst During the creation of a Stereo Analyst feature project various feature classes are selected The selected feature classes are stored as feature class files fcl in a feature project directory you select Unique color and attribute information can be defined for each selected feature class The contents of a Stereo Analyst feature class vary according to the feature type Point polyline and polygon feature class files contain different information The following general information characterizes each feature class Feature Class Name The feature class name can be defined within the General tab of the Create Custom Class dialog The feature class name is the name displayed within the Fe
25. real world applications and scenarios Since its inception and introduction GIS was designed to represent the Earth and its associated geography Vector data has been accepted as the primary format for representing geographic information For example a road is represented with a line and a parcel of land is represented using a series of lines to form a polygon Various approaches have been used to collect the vector data used as the fundamental building blocks of a GIS These include e Using a digitizing table to digitize features from cartographic topographic census and survey maps The resulting features are stored as vectors Feature attribution occurs either during or after feature collection e Scanning and georeferencing existing hardcopy maps The resulting images are georeferenced and then used to digitize and collect geographic information For example this includes scanning existing United States Geological Survey USGS 1 24 000 quad sheets and using them as the primary source for a GIS e Ground surveying geographic information Ground Global Positioning System GPS total stations and theodolites are commonly used for recording the 3D locations of features The resulting information is commonly merged into a GIS and associated with existing vector data sets e Outsourcing photogrammetric feature collection to service bureaus Traditional stereo plotters and digital photogrammetry workstations are used to collect hig
26. set as your Output Directory in the User Interface Session preferences 2 Click in the Project Name field of the Overview tab and type the name western_features then press Enter on your keyboard 3 Click in the Description field and type Tour Guide Example and the current date In the Features Classes tab you are able to select the specific features you wish to digitize in the DSM As you can see in the following series of steps the Feature Classes tab is neatly divided into types of features for example water buildings and streets which better enables you to select specific feature types you want If you edit feature class properties in a feature project the next time you save the project you are prompted as to whether or not you want to save the display properties and attributes changes to the global feature class If you select Yes the global feature class is permanently altered If you select No then the display properties and attributes changes are only saved to the feature class in the current project 1 In the Feature Project dialog click the Feature Classes tab The various features available to you display in the Feature Classes tab Feature Project Gere Pinte Clare lena Mcd Caec clsiset ho icles i uli poaait Categor gua Area E esten atentas Frane mm Sunken Foc Selina Claes As you select classes they display here Cia 04 Gregis Lissie giure
27. the main memory Parallactic angle The resulting angle made by eyes focusing on the same point in the distance The angle created by intersection Parallax Displacement of a ground point appearing in a stereopair as a function of the position of the sensors at the time of image capture You can adjust parallax in both the X and the Y direction so that the image point in both images appears in the same image space Terms 284 Stereo Analyst Perspective center 1 A point in the image coordinate system defined by the x and y coordinates of the principal point and the focal length of the sensor 2 After triangulation a point in the ground coordinate system that defines the position of the sensor relative to the ground Phi 9 A measurement used to define camera or sensor rotation in exterior orientation Phi is rotation about the photographic y axis Photogrammetric quality scanners Special devices capable of high image quality and excellent positional accuracy Use of this type of scanner results in geometric accuracy similar to traditional analog and analytical photogrammetric instruments Photogrammetry The art science and technology of obtaining reliable information about physical objects and the environment through the process of recording measuring and interpreting photographic images and patterns of electromagnetic radiant imagery and other phenomena American Society of Photogrammetry 1980 Pixel Abbreviated
28. 3D geographic information using most 3D geographic imaging systems During the collection of 3D GIS data the attribute information associated with a vector layer can be edited Attribute tables can be displayed with the DSM during the collection of 3D GIS data You can work with attribute tables in Collecting and Editing 3D GIS Data Interpreting the DSM during the capture of 3D GIS data allows for the collection maintenance and input of nonspatial information such as the type of tree and zoning designation in an urban area Automated attribution techniques simultaneously populate a GIS during the collection of 3D features with such data as area perimeter and elevation Additional qualitative and quantitative attribution information associated with a feature can be input during the collection process Workflow 26 B 3D GIS Data from Imagery 3D GIS Applications Forestry Stereo Analyst The products resulting from using 3D geographic imaging techniques include orthorectified imagery DTMs DSMs 3D features 3D measurements and attribute information associated with a feature Using these primary sources of geographic information additional GIS data can be collected updated and edited An increasing trend in the geocommunity involves the use of 3D data in GIS spatial modeling and analysis The 3D GIS data collected using 3D geographic imaging can be used for spatial modeling GIS analysis and 3D visualization and
29. 3D geographic representations of buildings are required for radio engineering analysis and LOS between building rooftops in urban and rural environments Accurate 3D building information is required to properly perform the analysis Once the 3D data has been collected it can be used for radio coverage planning system propagation prediction plotting and analysis network optimization antenna siting and point to point inspection for signal validation 3D GIS Data from Imagery 29 E Next Next you can learn about the principles of photogrammetry and how Stereo Analyst uses those principles to provide accurate results in your GIS Stereo Analyst Next 30 Photogrammetry B Introduction This chapter introduces you to the general principles that form the foundation of digital mapping and photogrammetry EJ Principles of Photogrammetric principles are used to extract topographic information from aerial photographs and imagery Figure 6 Photog rammetry illustrates rugged topography This type of topography can be viewed in 3D using Stereo Analyst Figure 6 Topography What is Photogrammetry is the art science and technology of obtaining Photogrammetry reliable information about physical objects and the environment through the process of recording measuring and interpreting photographic images and patterns of electromagnetic radiant imagery and other phenomena American Society of Photogrammetry 1980 Photogrammetry was
30. B appear on the left photograph L4 at image positions a and b respectively Due to the forward motion of the aircraft during photographic exposure the same two ground points appear on the right photograph L5 at image positions a and b Since ground point A is at a higher elevation the movement of image point a to position a on the right image is larger than the image movement of point b This can be attributed to x parallax Figure 29 illustrates that the parallax associated with ground point A Pa is larger than the parallax associated with ground point B Pb Figure 29 Parallax Comparison Between Points Thus the amount of x parallax is influenced by the elevation of a ground point Since the degree of topographic relief varies across a stereopair the amount of x parallax also varies In essence the brain perceives the variation in parallax between the ground and various features and therefore judges the variations in elevation and height Figure 30 illustrates the difference in elevation as a function of x parallax Stereo Models and Parallax 65 Y parallax Stereo Analyst Figure 30 Parallax Reflects Change in Elevation X parallax Higher elevation 260 meters X parallax Lower elevation 250 meters X Using 3D geographic imaging techniques Stereo Analyst translates and transforms the x parallax information associated with features recorded on a stereopair into quantitative heigh
31. For example a building is represented with a polygon having only X and Y coordinate information To create a 3D GIS involves creating DTMs digitizing contour lines or surveying the geography of the Earth to obtain 3D coordinate information Once collected the 3D information is merged with the 2D GIS to create a 3D GIS Each approach is ineffective in terms of the time cost and accuracy associated with collecting the 3D information for a 2D GIS e The cost associated with outsourcing core digital mapping to specialty shops is expensive in both dollars and time Also performing regular GIS data updates requires additional outsourcing With the advent of image processing and remote sensing systems the use of imagery for collecting geographic information has become more frequent Imagery was first used as a reference backdrop for collecting and editing geographic information including vectors for a GIS This imagery included e raw photography e geocorrected imagery and e orthorectified imagery Each type of imagery has its advantages and disadvantages although each is limited to the collection of geographic information in 2D To accurately represent the Earth and its geography in a GIS the information must be obtained directly in 3D regardless of the application Stereo Analyst provides the solution for directly collecting 3D information from stereo imagery Stereo Analyst Introduction 12 a Image Preparation for a
32. Helava U V 1988 Object space least square correlation International Archives of Photogrammetry and Remote Sensing Vol 27 Part B3 p 321 International Society for Photogrammetry and Remote Sensing ISPRS The Society at http www isprs org society html 29 May 2000 Jacobsen K 1980 Vorschl ge zur Konzeption und zur Bearbeitung von B ndelblockausgleichungen Ph D dissertation wissenschaftliche Arbeiten der Fachrichtung Vermessungswesen der Universit t Hannover No 102 1982 Programmgesteuerte Auswahl der zus tzlicher Parameter Bildmessungund Luftbildwesen p 213 1984 Experiences in blunder detection ISPRS 15th Works 270 Congress Rio de Janeiro 1994 Combined block adjustment with precise differential GPS data International Archives of Photogrammetry and Remote Sensing Vol 30 Part B3 p 422 Jensen J R 1996 Introductory Digital Image Processing Prentice Hall Englewood Cliffs NJ Keating T J P R Wolf and F L Scarpace 1975 An Improved Method of Digital Image Correlation Photogrammetric Engineering and Remote Sensing Vol 41 No 8 p 993 Konecny G 1994 New trends in technology and their applications photogrammetry and remote sensing from analog to digital Thirteenth United Nations Regional Cartographic Conference for Asia and the Pacific Beijing 9 15 May 1994 Konecny G and G Lehmann 1984 Photogrammetrie Walt
33. I properly orient the two photographs for stereo viewing You can use the Left Buffer icon to manually superimpose the feature in this case the stadium identified on the left image with the corresponding feature on the right image Click the Left Buffer icon Lj on the Digital Stereoscope Workspace toolbar Click and hold to select the left image la left img the red image and drag it over the right image so that the common feature overlaps as depicted in the following illustration Adjust and Rotate the Display 89 Left image z gt x Right image J x 3 Notice that the principal point on the left and right images is separated along the y direction This is incorrect for stereo viewing Consult the following illustration y Principal points of each image e J X In order to obtain a 3D stereo view the principal point on the left and right images must be separated along the x direction If the principal points are not separated along the x direction the images must be rotated If you have followed the steps correctly to this point your stereopair should look similar to the following illustration Stereo Analyst Adjust and Rotate the Display 90 Rotate the Images Stereo Analyst Left image Area of overlap Right image Click the Left Buffer icon Lj again to deselect it Click hold and drag the stereopair until it is positioned in the middle of the
34. Kappa of each image as they existed when the image was captured Ensure that the linear and angular units are known zx For detailed information see Interior Orientation and Exterior Orientation Once all of the necessary information has been entered the resulting output is a block file which can also be used in LPS Project Manager The block file format and structure used in Stereo Analyst are identical to the file format and structure used in LPS Project Manager and LPS Automatic Terrain Extraction ATE What is a Block File A block file is a file containing two or more images that form a DSM In most block files there are more than two images therefore you can choose from a number of different image combinations to view in stereo Moreover a block file contains information such as sensor or camera type projection horizontal and vertical units angle units rotation system photo direction and interior and exterior orientation information When this information is provided to Stereo Analyst the need for parallax adjustment in the Digital Stereoscope Workspace is eliminated Stereo Analyst utilizes the accurate sensor model information to automatically adjust parallax to provide a clear DSM Stereo Analyst Introduction 112 B Getting Started Stereo Analyst Stereo Analyst provides the capability to create one oriented DSM at a time LPS Project Manager on the other hand can be
35. Main View When you rotate images you turn them in incremental degrees to the right clockwise and left counterclockwise To see this more clearly you can zoom out so that the extent of both images is visible in the Main View Click the Rotate Tool icon G Move your mouse into the Main View and double click in the center portion of the overlap area which appears to be gray in Color Anaglyph mode A target appears in the overlap area Adjust and Rotate the Display 91 Target 3 Click and hold the left mouse button inside the target see the following illustration and move the mouse horizontally to the right to create an axis Extend the axis until the cursor is located outside of the image area For the purpose of illustration the area inside the target is red Click anywhere inside the red area to create an axis Start 360 a Y Rotate the image in the Main View relative to 270 90 the target Clockwise the angles are 90 180 de El 279 and 360 degrees 180 The axis originates from the center of the target to a position you set A longer line axis provides greater flexibility in rotating the images A shorter axis provides greater sensitivity to the rotation process It is recommended that a longer axis be used for rotating the images To obtain a longer axis move the cursor farther away from the center point of the target 4 Move the mouse 90 degrees clockwise Stereo Analyst Adjust and Ro
36. Raw aerial photography and satellite imagery have large geometric distortion that is caused by various systematic and nonsystematic factors Photogrammetric processes eliminate these errors most efficiently and provide the most reliable solution for collecting geographic information from raw imagery Photogrammetry is unique in terms of considering the image forming geometry utilizing information between overlapping images and explicitly dealing with the third dimension elevation Photogrammetric techniques allow for the collection of the following geographic data e 3D GIS vectors e DTMs which include TINs and DEMs e orthorectified images e DSMs e topographic contours In essence photogrammetry produces accurate and precise geographic information from a wide range of photographs and images Any measurement taken on a photogrammetrically processed photograph or image reflects a measurement taken on the ground Rather than constantly go to the field to measure distances areas angles and point positions on the surface of the Earth photogrammetric tools allow for the accurate collection of information from imagery Photogrammetric approaches for collecting geographic information save time and money and maintain the highest accuracies During photographic or image collection overlapping images are exposed along a direction of flight Most photogrammetric applications involve the use of overlapping images By using more than one i
37. Stereo Analyst In this tour guide you are going to work with an LPS Project Manager block file You can type coordinates into the Position tool and see how the display drives to that point Then you can visualize the point in stereo in the Main View or OverView and in mono in the Left and Right Views In this tour guide you are going to work with an LPS Project Manager block file that has many stereopairs Using the 3D Measure tool you can digitize points lines and polygons These measurements are recorded in units corresponding to the coordinate system of the image which is in meters You can also get more precise information such as angles and elevations In this tour guide you are going to set up a new feature project which includes selecting a stereopair You can then collect features from the stereopair You are also going to select types of features to collect Also you can learn how to create a custom feature class You can learn how to use the feature collection and editing tools as well as the different modes associated with feature collection In this tour guide you can learn how to add realistic textures to your models You first obtain digital imagery of the building or landmark then you map that imagery to the model using Texel Mapper in Stereo Analyst This manual is part of a suite of on line documentation that you receive with ERDAS IMAGINE software There are two basic types of documents digital hardcopy do
38. WS daper Point 5 is the first vertex of another roof l Use the scroll bar to see the fifth line of data Point 5 Pt 5 476914 321931 4761270 384610 meters 254 2870 meters This means that the elevation between the various points on the roof changed by less than a meter Continue to scroll down to view the rest of the results in the 3D Measure tool text field You can also use the Terrain Following Cursor to improve the accuracy of your Z elevation measurements You can save the measurements to a text file for use in other applications and products In the 3D Measure tool click the Save icon a Navigate to a directory where you have write permission In the Enter text file to save dialog click in the File name section Save the Measurements 168 mier head llle in save Fe Navigate to a directory in which you have write Lack irn Joa leur permission Name the file here Filet of ye Means eei ZB Filet 1 Subedesctones 0 Mathai SETH Epic Fiee 4 Next Stereo Analyst Type the name western meas then press Enter on your keyboard The mes file extension is automatically appended Click OK in the Enter text file to save dialog You can now access the file any time you like for use in other applications What can you do with an mes file Using a mes file that you create with the Stereo Analyst 3D Measure tool you can import the
39. and determined Photogrammetric sensor modeling techniques define the specific information associated with a camera sensor as it existed when the imagery was captured This information includes both internal and external sensor model information Internal sensor model information describes the internal geometry of the sensor as it exists when the imagery is captured For aerial photographs this includes the focal length lens distortion fiducial mark coordinates and so forth This information is normally provided to you in the form of a calibration report For digital cameras this includes focal length and the pixel size of the charge coupled device CCD sensor For satellites this includes internal satellite information such as the pixel size the number of columns in the sensor and so forth If some of the internal sensor model information is not available for example in the case of historical photography sophisticated techniques can be used to determine the internal sensor model information This technique is normally associated with performing a bundle block adjustment and is referred to as self calibration External sensor model information describes the exact position and orientation of each image as they existed when the imagery was collected The position is defined using 3D coordinates The orientation of an image at the time of capture is defined in terms of rotation about three axes Omega o Phi q and Kappa x see Fi
40. and visually interpret the location of the 3D floating cursor over the feature Compute X Y Coordinate and Z Elevation Accuracy 1 Fifth Check Point Stereo Analyst If necessary adjust the image so that the feature is within the crosshair using the Enable Update option in the Position tool Record the new X and Y coordinate positions then subtract the old values from the new values to determine accuracy If necessary adjust the height of the cursor Record the new Z coordinate then subtract the old value from the new value to determine accuracy Check that Enable Update button is not active and the Zoom is set to approximately 1 0 In the Position tool type the following X Y and Z values respectively 477193 83 4761458 69 and 257 36 Use the Position Tool 142 3 Position the cursor and visually interpret the location of the 3D floating cursor over the feature Compute X Y Coordinate and Z Elevation Accuracy 1 If necessary adjust the image so that the feature is within the crosshair using the Enable Update option in the Position tool 2 Record the new X and Y coordinate positions then subtract the old values from the new values to determine accuracy 3 If necessary adjust the height of the cursor 4 Record the new Z coordinate then subtract the old value from the new value to determine accuracy Sixth Check Point 1 Check that Enable Update button is not active and the Zoom is set t
41. are satisfactorily minimized Once the least squares adjustment is completed the block triangulation results include e final exterior orientation parameters of each image in a block and their accuracy e final interior orientation parameters of each image in a block and their accuracy e X Y and Z tie point coordinates and their accuracy e adjusted GCP coordinates and their residuals and e image coordinate residuals The results from the block triangulation are then used as the primary input for the following tasks e stereopair creation e feature collection e highly accurate point determination e DEM extraction Digital Mapping Solutions 58 Automatic Gross Error Detection Next Stereo Analyst e orthorectification NOTE Stereo Analyst uses the results from the block triangulation for the automatic display and creation of DSMs Normal random errors are subject to statistical normal distribution In contrast gross errors refer to errors that are large and are not subject to normal distribution The gross errors among the input data for triangulation can lead to unreliable results Research during the 80s in the photogrammetric community resulted in significant achievements in automatic gross error detection in the triangulation process for example Kubik 1982 Li 1983 Li 1985 Jacobsen 1980 El Hakin 1984 and Wang 1988 Methods for gross error detection began with residual checking using data snooping an
42. attribute information to the feature such as the name of the road if you wish Attribute table An attribute table is automatically created when you digitize 3D features using Stereo Analyst The attribute table appears at the bottom of the Stereo Analyst window in a bucket Attribute tables contain default information depending on the type of feature they represent For example an attribute table detailing road features has a length attribute Attribution Attribution is attribute data associated with a feature See Attribute Base height ratio The ratio between the average flying height of the camera and the distance between where the two overlapping images were captured b h See Eye base to height ratio Block file A block file has the blk extension Block files contain at least one stereopair that is in a coordinate system A block file may also contain two or more sets of stereo images that you can use for feature extraction and viewing In that case you can use the Stereo Pair Chooser to select which stereopair of the block file you want to use in analysis Block triangulation The process of establishing a mathematical relationship between images the camera or sensor model and the ground The information derived is necessary for orthorectification DEM generation and stereopair creation Breakline An elevation polyline in which each vertex has its own X Y Z value Bucket One of three sections located in the lowe
43. both of the images from which to create an oriented DSM displayed in the Digital Stereoscope Workspace you can open the Create Stereo Model dialog Stereo Analyst provides the Create Stereo Model dialog to enable you to create oriented DSMs from individual images that have associated sensor model information The resulting DSM is stored as a block file From the toolbar of the Digital Stereoscope Workspace click the Create Stereo Model icon i You can also open the Create Stereo Model dialog by selecting Utility gt Create Stereo Model Tool The Create Stereo Model dialog opens on the Common tab Open the Create Stereo Model Dialog 117 Creale Seres Model You enter the name of the new LPS Project Manager block file here The Create Stere Model dialog opens on the Common tab You can navigate to a specific directory via the Block filename icon om Ij seen Degrees Crea Pri Fas ae Za la a Name the Block File 1 In the Create Stereo Model dialog click the Block filename icon ca NOTE If you are running Stereo Analyst in conjunction with ERDAS IMAGINE the default output directory is determined by the Default Output Directory you have set in the User Interface 8 Session category of your ERDAS IMAGINE Preferences The Block filename dialog opens Black filename meagre SEME ppan uia yal Y iur Hew D Templates AA Name the IMAGINE LPS Project Manager block file here
44. bureaus and production shops Using traditional stereoplotters and digital photogrammetric workstations 3D geographic information is collected from stereo models The 3D geographic information may include DTMs 3D features and spatial and nonspatial attribution ready for input in your GIS database Using these sophisticated and advanced tools the procedures required for collecting 3D geographic information become costly The use of such equipment is generally limited to highly skilled photogrammetrists To preserve the investment made in a GIS a new approach is required for the collection and maintenance of geographic data and information in a GIS The approach must provide the ability to e Access and use readily available up to date sources of information for the collection of GIS data and information e Accurately collect both 2D and 3D GIS data from a variety of sources Geographic Imaging 19 e Minimize the time associated with preparing collecting and editing GIS data e Minimize the cost associated with preparing collecting and editing GIS data e Collect 3D GIS data directly from raw source data without having to perform additional preparation tasks e Integrate new sources of imagery easily for the maintenance and update of data and information in a GIS The only solution that can address all of the aforementioned issues involves the use of imagery Imagery provides an up to date highly accurate representati
45. by Space Imaging including IRS 1A IRS 1B IRS 1C and IRS 1D Inertial navigation system INS A technique that provides initial approximations to exterior orientation INS See Inertial navigation system Interior orientation Defines the geometry of a sensor that captured an image This information is defined in fiducial marks in the case of cameras Definition of the light rays passing from the perspective center through the image plane and onto the ground Moffit and Mikhail 1980 International Society of Photogrammetry and Remote Sensing ISPRS An organization devoted to the development of international cooperation for the advancement of photogrammetry and remote sensing and their application For more information visit the web site at http www isprs org ISPRS 2000 IRS See Indian Remote Sensing Satellite ISPRS See International Society of Photogrammetry and Remote Sensing Kappa x A measurement used to define camera or sensor rotation in exterior orientation Kappa is rotation about the photographic z axis Landsat A series of Earth orbiting satellites that gather imagery Operated by EOSAT Least squares adjustment A technique used to determine the most probable positions of exterior orientation The least squares adjustment technique reduces error Terms 282 Stereo Analyst Lens distortion Caused by the instability of the camera lens at the time of data capture Lens distortion makes the
46. corner of the tower then move the mouse and continue to digitize along the roof line adjusting the cursor elevation and x parallax as necessary When you have completely digitized the roof of the tower double click to close the polygon The filled polygon which corresponds to the roof of the tower displays in the Main View Collect Building Features 190 A filled polygon indicates that the feature is not selected Use the 3D Polygon Extend Tool 1 Inthe Main View position your cursor at a location on the ground close to the building In this case we suggest you use the corner of a nearby sidewalk 2 Using the Left and Right Views as a guide adjust the height of the cursor with the mouse wheel until the cursor rests on the ground Stereo Analyst Collect Building Features 191 Stereo Analyst The elevation of this sidewalk provides information for the 3D Polygon Extend tool Click on a line segment of the polygon you created Note that the line segments are greatly offset due to x parallax Click to select the 3D Polygon Extend tool from the feature toolbar Click to select any one of the vertices that makes up the roof line Left click outside the polygon to deselect it Stereo Analyst creates a 3D feature that touches the ground Collect Building Features 192 7 Click the Zoom to Full Extent icon ma E 2 You can see the features digitized in the views View the Feature in the 3D Fea
47. curvature film and scanning distortion and measurement errors Measurements made on data sources that have not been rectified for the purpose of collecting geographic information are not reliable Geoprocessing techniques warp stretch and rectify imagery for use in the collection of 2D geographic information These techniques include geocorrection and orthorectification which establish a geometric relationship between the imagery and the ground The resulting 2D image sources are primarily used as reference backdrops or base image maps on which to digitize geographic information Image Preparation for a GIS 15 Figure 2 Spatial and Nonspatial Information for Local Government Applications I Fl m al T jit De 41 to 0 a Ey ge oe Geocorrection Stereo Analyst Conventional techniques of geometric correction or geocorrection such as rubber sheeting are based on approaches that do not directly account for the specific distortion or error sources associated with the imagery These techniques have been successful in the field of remote sensing and GIS applications especially when dealing with low resolution and narrow field of view satellite imagery such as Landsat and SPOT General functions have the advantage of simplicity They can provide a reasonable geometric modeling alternative when little is known about the geometric nature of the image data Problems Conventional techniques generally process the images
48. dm s D ae Hi om e Es d Tit tae Tori G A Pixel coordinates and image scale display here a Adjust Display Now that you have an image displayed in the Main View you can Resolution manipulate its display Your mouse allows you to roam and zoom throughout the image Next you can practice techniques Zoom NOTE This exercise is easier to complete if the Digital Stereoscope Workspace is enlarged to fill your display area Stereo Analyst Adjust Display Resolution 80 1 Inthe Main View position your cursor over the stadium in the left hand portion of the image indicated with a red circle in the following picture The stadium is located in the area ER indicated with a circles A oc 2 Hold down the wheel and push the mouse forward and away from you Hold down the whe Move the mouse in this direction If your mouse is not equipped with a wheel use the middle mouse button or the Control key and the left mouse button simultaneously while moving the mouse forward and away from you 3 If necessary click and hold the left mouse button then drag the image to position the stadium in the middle of the Main View 4 Continue to move the mouse until the stadium appears at a resolution you can view comfortably Note that the image scale displays in the status area of the Digital Stereoscope Workspace Stereo Analyst Adjust Display Resolution 81 What is image scale An image scale SI of 1 indica
49. feature collection capabilities of Stereo Analyst changes and variations in elevation perceived by the brain can be translated to reflect real world 3D information Figure 26 shows an example of a 3D Shapefile created using Stereo Analyst which displays in IMAGINE VirtualGIS Principles of Stereo Viewing 63 Figure 26 3D Shapefile Collected in Stereo Analyst D 585 METAF El Stereo Models and Stereo models provide a permanent record of 3D information Parallax pertaining to the given geographic area covered within the overlapping area of two images Viewing a stereo model in stereo presents an abundant amount of 3D information to you The availability of 3D information in a stereo model is made possible by the presence of what is referred to as stereoscopic parallax There are two types of parallax x parallax and y parallax X parallax Figure 27 illustrates the image positions of two ground points A and B appearing in the overlapping areas of two images Ground point A is the top of a building and ground point B is the ground Figure 27 Left and Right Images of a Stereopair Principal Point 1 Principal Point 2 Stereo Analyst Stereo Models and Parallax 64 Stereo Analyst Figure 28 illustrates a profile view of the stereopair and the corresponding image positions of ground point A and ground point B Figure 28 Profile View of a Stereopair L4 Lo a Nb a b O o A B Ground points A and
50. have been extended to include the processing of oblique and terrestrial photography and imagery Given the use of computer hardware and software for photogrammetric processing various image file formats can be used These include TIF JPEG GIF Raw and Generic Binary and Compressed imagery along with various software vendor specific file formats The workflow associated with creating 3D GIS data is linear The hierarchy of processes involved with creating highly accurate geographic information can be broken down into several steps which include e Define the sensor model e Measure GCPs e Collect tie points automated e Perform bundle block adjustment that is aerial triangulation e Extract DTMs automated e Orthorectify the images e Collect and attribute 3D features This workflow is generic and does not necessarily need to be repeated for every GIS data collection and maintenance project For example a bundle block adjustment does not need to be performed every time a 3D feature is collected from imagery Workflow 22 Defining the Sensor Model Measuring GCPs Stereo Analyst A sensor model describes the properties and characteristics associated with the camera or sensor used to capture photography and imagery Since digital photogrammetry allows for the accurate collection of 3D information from imagery all of the characteristics associated with the camera sensor the image and the ground must be known
51. in Stereo Analyst extend the perception and interpretation of depth to include the measurement and collection of 3D information Stereo Analyst Principles of Stereo Viewing 61 How it Works Stereo Analyst A true stereo effect is achieved when two overlapping images a stereopair or photographs of a common area captured from two different vantage points are rendered and viewed simultaneously The stereo effect or ability to view with measurable depth perception is provided by a parallax effect generated from the two different acquisition points This is analogous to the depth perception you achieve by looking at a feature with your two eyes The distance between your eyes represents the two vantage points similar to two independent photos as in Figure 24 Figure 24 Two Overlapping Photos TEN The importance is that by viewing the surface of the Earth in stereo you can interpret measure and delineate map features in 3D The net benefit is that many map features are more interpretable with a higher degree of accuracy in stereo than in 2D with a single image Figure 25 shows a stereo view Principles of Stereo Viewing 62 Stereo Analyst Figure 25 Stereo View When viewing the features from two perspectives the left photo and the right photo the brain automatically perceives the variation in depth between different objects and features as a difference in height For example while viewing a building in st
52. in the Destination Box than the Destination Box is stretched slightly Adjust the vertices S0 the curbs align Select the Preview radio button on the Image Edit Options menu to see a preview of what the edited image will look like If you are satisfied with the Preview click Apply Otherwise continue adjusting the vertices until you are satisfied After you click Apply you will see a Clean Preview This preview shows you the result of the editing operation without the Source and Destination Boxes You may continue experimenting with the Image Edit Options and remove the remaining car the trees the power lines and the lamp post if you wish To resume editing select the Edit radio button on the Image Edit Options menu To see the results of your editing on the model enter the Model Options mode by clicking the x button on the Texel Mapper toolbar The model display Note that the compact car and any other artifact that you edited out is no longer visible on the textures front of the building Editing the Texture 232 Tiling a Texture Adding the Texture to the Tile Library Tiling Multiple Faces Stereo Analyst Now you have textured the three faces of the building for which you have pictures The other sides of the building though still need textures and there are no digital images for those faces You need a simple way to quickly texturize the remaining sides This can be done by t
53. invented in 1851 by Laussedat and has continued to develop over the last century plus Over time the development of photogrammetry has passed through the phases of plane table photogrammetry analog photogrammetry analytical photogrammetry and has now entered the phase of digital photogrammetry Konecny 1994 Stereo Analyst Principles of Photogrammetry 31 The traditional and largest application of photogrammetry is to extract topographic and planimetric information for example topographic maps from aerial images However photogrammetric techniques have also been applied to process satellite images and close range images to acquire topographic or nontopographic information of photographed objects Topographic information includes spot height information contour lines and elevation data Planimetric information includes the geographic location of buildings roads rivers etc Prior to the invention of the airplane photographs taken on the ground were used to extract the relationship between objects using geometric principles This was during the phase of plane table photogrammetry In analog photogrammetry starting with stereo measurement in 1901 optical or mechanical instruments such as the analog plotter were used to reconstruct 3D geometry from two overlapping photographs The main product during this phase was topographic maps Figure 7 Analog Stereo Plotter In analytical photogrammetry the computer replaces s
54. is image space coordinate system and ground space coordinate system Oriented stereopair An oriented stereopair has a known interior camera or sensor internal geometry and exterior camera or sensor position and orientation orientation The y parallax of an oriented stereopair has been improved Additionally an oriented stereopair has geometric and geographic information concerning the surface of the Earth and a ground coordinate system Features and measurements taken from an oriented stereopair have X Y and Z coordinates Orthorectification A photogrammetric technique used to eliminate errors in DSMs efficiently which allows accurate and reliable information LPS Project Manager makes use of orthorectification to obtain a high degree of accuracy Overlay 1 Afunction that creates a composite file containing either the minimum or the maximum class values of the input files Overlay sometimes refers generically to a combination of layers 2 The process of displaying a classified file over the original image to inspect the classification OverView In an OverView you can see the entire DSM displayed in a stereo view OverViews can render DSMs in both mono and stereo Paging When data is read from the hard disk into main memory it is referred to as paging The term paging originated from blocks of disk data being read into main memory in fixed sizes called pages Dynamic paging brings manageable subsets of a large data set into
55. la sabe mg doi not burns Farior ppl lea camped over a ra rad peed Luena Cni Cus den der peramanee depending on the sre of he image Waki pou B panej leet rue o REN NOTE The alert to create pyramid layers only occurs the first time you open the new image in the Digital Stereoscope Workspace Once pyramid layers are created they remain with the image in a separate rrd file Open the New DSM 102 m K E BS LEE Fm a imi Mi WS RSS Ane BORER v Gu 6 Use the mouse to zoom into and out of the DSM in the Digital Stereoscope Workspace NOTE Now that the left and right images have been merged into one you can no longer adjust the x parallax and the Y parallax Therefore you may wish to zoom into a smaller area of an image before using View to Image That way the parallax is properly adjusted for a specific portion of the image 7 Click the Clear View icon amp 8 Select File gt Exit Workspace to close Stereo Analyst if you wish a Adjusting X X parallax is a function of elevation Therefore as elevation varies P 11 throughout the geographic area covered by the image so does the arallax amount of x parallax The following two figures illustrate varying degrees of x parallax over the same geographic area Figure 5 1 a gives a good stereo view of only the front driveway of the building Stereo Analyst Adjusting X Parallax 103 E Adjusting Y Parallax Stereo Analyst Figure 37
56. manuals for additional information NOTE Notes give additional instruction Blue Box These boxes contain technical information which includes theory and stereo concepts The information contained in these boxes is not required to execute steps in the tour guides or other chapters of this manual Stereo Analyst Conventions Used in This Book xvi Theory Stereo Analyst 1 Stereo Analyst 12 Introduction to Stereo Analyst Introduction Unlike traditional GIS data collection techniques Stereo Analyst saves you money and time in image preparation and data capture With Stereo Analyst you can e Collect true real world three dimensional 3D geographic information in one simple step and to higher accuracies than when using raw imagery geocorrected imagery or orthophotos e Use timesaving automated feature collection tools for collecting roads buildings and parcels e Attribute features automatically with attribute tables both spatial and nonspatial attribute information associated with a feature can be input during collection e Use high resolution imagery to simultaneously edit and update your two dimensional 2D GIS with 3D geographic information e Collect 3D information from any type of camera including aerial video digital and amateur e Measure 3D information including 3D point positions distances slope area angles and direction e Collect X Y Z mass points and breaklines
57. one at a time They cannot provide an integrated solution for multiple images or photographs simultaneously and efficiently It is very difficult if not impossible for conventional techniques to achieve a reasonable accuracy without a great number of GCPs when dealing with high resolution imagery images having severe systematic and or nonsystematic errors and images covering rough terrain such as mountain areas Image misalignment is more likely to occur when mosaicking separately rectified images This misalignment could result in inaccurate geographic information being collected from the rectified images As a result the GIS suffers Image Preparation for a GIS 16 Furthermore it is impossible for geocorrection techniques to extract 3D information from imagery There is no way for conventional techniques to accurately derive geometric information about the sensor that captured the imagery Solution Techniques used in LPS Project Manager and Stereo Analyst overcome all of these problems by using sophisticated techniques to account for the various types of error in the input data sources This solution is integrated and accurate LPS Project Manager can process hundreds of images or photographs with very few GCPs while at the same time eliminating the misalignment problem associated with creating image mosaics In short less time less money less manual effort and more geographic fidelity can be realized using the photogrammetric
58. positional accuracy of the image points less reliable Line of sight LOS Area that can be viewed along a straight line without obstructions Line segment The area between vertices of a polyline or polygon Line segments can be edited and deleted using Stereo Analyst feature editing tools Linear interpolation Data file values are plotted in a graph relative to their distances from one another creating a visual linear interpolation Lithological Relating to rocks LOS see Line of sight Map coordinate system A map coordinate system that expresses locations on the surface of the Earth using a particular map projection such as Universal Transverse Mercator UTM State Plane or Polyconic Metric photogrammetry The process of measuring information from photography and satellite imagery Mono A mono view is that in which there is only one image There are not two images to create a stereopair You cannot see in 3D using a mono view Mosaicking The process of piecing together images side by side to create a larger image Multiple points Multiple points can be collected from a DSM to create a TIN or DEM Like a single point multiple points have X Y and Z coordinate values See also TIN and DEM Nadir The area on the ground directly beneath the detectors of a scanner Nearest neighbor A resampling method in which the output data file value is equal to the input pixel whose coordinates are closest to the retrans
59. reu pesci Ifyou decide you do not want to collect a feature of a certain type select it then click the Unselect P Pagi button wood Day Vegetation echoed Sen Gresie Luton ashar Clair Enter Information into Now that you have named your project and selected feature classes the Stereo Model you can use the Stereo Model tab to select the block file and DSM from which you want to collect features 1 From the Feature Project dialog click the Stereo Model tab Feature Project Care enue Glaus Slee ideal Select the IMAGINE i LPS Project Manager e block file using this icon l Stereo models in the AAA LPS Project Manager block file display here You can also access the Stereo Pair Chooser from this tab Detach Sock 2 In the Stereo Model tab click the Open icon i The Stereo Model dialog opens Stereo Analyst Create a New Feature Project 179 Select the western_accuracy block file Fieri ai hor PAGINE hecho lock File bil Flors i Ape Pec gre ECT m pleni et egens actu blk x 3 Navigate to the IMAGINE HOME examplesWWestern directory and select the file named western accuracy blk 4 Click OK in the Stereo Model dialog The Stereo Model tab is now populated with the information Now you can choose a DSM from which to collect features LZ mur i Deme Festa Clam Sheen Moda Senec Model bike metil btu bk umeni lene Fea Feature Collect This i
60. rights in MrSID technology including without limitation a The U S Government has a non exclusive nontransferable irrevocable paid up license to practice or have practiced throughout the world for or on behalf of the United States inventions covered by U S Patent No 5 710 835 and has other rights under 35 U S C 8 200 212 and applicable implementing regulations b If LizardTech s rights in the MrSID Technology terminate during the term of this Agreement you may continue to use the Software Any provisions of this license which could reasonably be deemed to do so would then protect the University and or the U S Government and c The University has no obligation to furnish any know how technical assistance or technical data to users of MrSID software and makes no warranty or representation as to the validity of U S Patent 5 710 835 nor that the MrSID Software will not infringe any patent or other proprietary right For further information about these provisions contact LizardTech 1008 Western Ave Suite 200 Seattle WA 98104 ERDAS ERDAS IMAGINE IMAGINE OrthoBASE Stereo Analyst and IMAGINE VirtualGIS are registered trademarks IMAGINE OrthoBASE Pro is a trademark of Leica Geosystems Geospatial Imaging LLC SOCET SET is a registered trademark of BAE Systems Mission Solutions Other companies and products mentioned herein are trademarks or registered trademarks of their respective owners Table of Contents Table of CONTEMES 40
61. satellite Satellites use onboard cameras to collect high resolution images of the surface of the Earth Figure 9 Satellite Terrestrial or ground based photographs and images are taken with the camera stationed on or close to the surface of the Earth Terrestrial and close range photographs and images are commonly used for applications involved with archeology geomorphology civil engineering architecture industry etc Oblique photographs and images are similar to aerial photographs and images except the camera axis is intentionally inclined at an angle with the vertical Oblique photographs and images are commonly used for reconnaissance and corridor mapping applications Digital photogrammetric systems use digitized photographs or digital images as the primary source of input Digital imagery can be obtained from various sources These include e digitizing existing hardcopy photographs Principles of Photogrammetry 34 Why use Photogrammetry E Image and Data Acquisition Stereo Analyst e using digital cameras to record imagery and e using sensors onboard satellites such as Landsat SPOT and IRS to record imagery This document uses the term imagery in reference to photography and imagery obtained from various sources This includes aerial and terrestrial photography digital and video camera imagery 35 mm photography medium to large format photography scanned photography and satellite imagery
62. simulation applications The following examples illustrate how 3D geographic imaging techniques can be used for applications in forestry geology local government water resource management and telecommunications For forest inventory applications an interpreter identifies different tree stands from one another based on height density crown cover species composition and various modifiers such as slope type of topography and soil characteristics Using a DSM a forest stand can be identified and measured as a 3D polygon 3D geographic imaging techniques are used to provide the GIS data required to determine the volume of a stand This includes using a DSM to collect tree stand height tree crown diameter density and area Using 3D DSMs with high resolution imagery various tree species can be identified based on height color texture and crown shape Appropriate feature codes can be directly placed and georeferenced to delineate forest stand polygons The feature code information is directly indexed to a GIS for subsequent analysis and modeling Figure 5 Use of 3D Geographic Imaging Techniques in Forestry 3D GIS Data from Imagery 27 Geology Based on the information collected from DSMs forestry companies use the 3D information in a GIS to determine the amount of marketable timber located within a given plot of land the amount of timber lost due to fire or harvesting and where foreseeable problems may arise due to har
63. source like hardcopy or digital maps These new tools significantly improve the reliability of GIS data and reduce the steps and time associated with populating a GIS with accurate information The backbone of 3D geographic imaging is digital photogrammetry Photogrammetry has established itself as the main technique for obtaining accurate 3D information from photography and imagery Traditional photogrammetry uses specialized and expensive stereoscopic plotting equipment Digital photogrammetry uses computer based systems to process digital photography or imagery With the advent of digital photogrammetry many of the processes associated with photogrammetry have been automated Over the last several decades the idea of integrating photogrammetry and GIS has intimidated many people The cost and learning curve associated with incorporating the technology into a GIS has created a chasm between photogrammetry and GIS data collection production and maintenance As a result many GIS professionals have resorted to outsourcing their digital mapping projects to specialty photogrammetric production shops Advancements in softcopy photogrammetry or digital photogrammetry have broken down these barriers Digital photogrammetric techniques bridge the gap between GIS data collection and photogrammetry This is made possible through the automated processes associated with digital photogrammetry Transforming imagery into 3D GIS data involves several pr
64. the following applications e Land use land cover mapping involves the identification and categorization of urban and rural land use and land cover Using DSMs 3D topographic information slope vegetation type soil characteristics underlying geological information and infrastructure information can be collected as 3D vectors e Land use suitability evaluation usually requires soil mapping DSMs allow for the accurate interpretation and collection of soil type slope soil suitability soil moisture soil texture and surface roughness As a result the suitability of a given infrastructure development can be determined e Population estimation requires accurate 3D high resolution imagery for determining the number of units for various household types The height of buildings is important 3D GIS Data from Imagery 28 e Housing quality studies require environmental information derived from DSMs including house size lot size building density street width and condition driveway presence absence vegetation quality and proximity to other land use types e Site selection applications require the identification and inventory of various geographic information Site selection applications include transportation route selection sanitary landfill site selection power plant siting and transmission line location Each application requires accurate 3D topographic representations geologic inventory soils inventory land use vegetatio
65. the new values to determine accuracy If necessary adjust the height of the cursor Record the new Z coordinate then subtract the old value from the new value to determine accuracy Now that you have checked and recorded the accuracy of the DSM you can close the Position tool and close the block file western accuracy blk In the Position tool click the Close icon x The Digital Stereoscope Workspace again occupies the entire window Click the Clear Viewer icon amp to empty the Digital Stereoscope Workspace Select File gt Exit Workspace to close Stereo Analyst if you wish Close the Position Tool 145 Next Stereo Analyst In the next tour guide you are going to work with another one of the tools you may find in Stereo Analyst the 3D Measure tool Using the Measure tool the following information can be collected 3D point coordinates slope and distance and elevation difference between two points area azimuth along a line the angle between three points Next 146 Measuring 3D Information Introduction The following tour guide describes the techniques associated with measuring 3D information in Stereo Analyst Using the 3D Measure tool the following information can be collected e 3D coordinates of a point e length of a line e slope of a line e azimuth of a line e difference in elevation Delta Z between the start point and end point of a line e area of a polygon e angle between t
66. to a parking lot which you are also going to digitize Digitize this forest to practice sharing borders with the adjacent parking lot 6 Click the Close icon X in the Position tool to maximize the display area 7 Adjust the zoom and x parallax as necessary Stereo Analyst Collect a Forest Feature 211 Select the Woods Feature and Digitize Stereo Analyst 1 From the Feature Class Palette click to select the Woods icon E oh From the feature toolbar select the Stream Digitizing tool s Once you select the Stream Digitizing icon it remains depressed in the feature toolbar indicating that it is active Move your mouse into the display area and position the cursor at the southern tip of the forest Ensure that the cursor is resting on the ground Left click hold and drag the mouse around the perimeter of the forest to collect it When you have completely digitized the forest double click to close the polygon The filled polygon of the forest feature displays in the Main View Next create a shared boundary with this parking lot Collect a Forest Feature 212 Stereo Analyst Create and Add a Custom Feature Class to the Palette 10 11 12 There is a parking lot that borders the forest This feature clearly shares a border with the forest you just digitized However there is not a feature class to represent it You can add feature classes even a custom feature class to the Featur
67. to simplify feature collection Specifically the steps you are going to execute in this example include e Create a new feature project e Create a custom feature class e Collect building features using collection tools e Collect roads and related features using collection tools e Collect a river feature using collection tools e Use the Stereo Pair Chooser e Collect a forest feature using collection tools e Check the attribute tables e Use selection criteria on attribute tables The data used in this tour guide covers the campus of The University of Western Ontario in London Ontario Canada The photographs were captured at a photographic scale of 1 6000 The photographs were scanned at a resolution of 25 microns The resulting ground coverage per pixel is 0 15 meters You may want to refer to the feature collecting tools reference and the feature editing tools reference in the Stereo Analyst On Line Help for tips on collecting and editing features Approximate completion time for this tour guide is 2 hours Stereo Analyst Introduction 171 H Getting Started H Create a New Feature Project Enter Information in the Overview Tab Type the name of the feature project here You must have both Stereo Analyst and the example files installed to complete this tour guide This tour guide was created in color anaglyph mode If you want your results to match those in this tour guide set your stereo m
68. tool type the value 477823 in the X field then press Enter on your keyboard Stereo Analyst Collect Roads and Related Features 198 Type 4761543 in the Y field then press Enter Type 251 58 in the Z field then press Enter Type 0 6 in the Zoom field then press Enter The following sidewalk displays in the Digital Stereoscope Workspace Collect this sidewalk feature Click the Close icon X in the Position tool to maximize the display area Adjust the zoom and x parallax as necessary so that the northern portion of the sidewalk is evident in the view Select the Sidewalk Feature and Digitize Stereo Analyst 1 From the Feature Class Palette click to select the Sidewalk icon FP Sube From the feature toolbar select the Parallel Line tool s Once you select the Parallel Line tool it remains depressed in the feature toolbar Move your mouse into the display area and position the cursor at the northernmost section of the sidewalk Adjust the cursor elevation by rolling the mouse wheel until it rests on the ground NOTE You may find this easier if you zoom into the image even more Click to digitize the first vertex on the left side of the sidewalk Move your mouse to the right side of the sidewalk At this time the display looks like the following Collect Roads and Related Features 199 First you establish the width of the feature you are going to collect by clicking a vertex on either side
69. tool is automatically placed at the bottom of the Digital Stereoscope Workspace Measurements can be points polylines or polygons and have X Y and Z coordinates You can also measure slope with the 3D Measure tool Position Tool Click this icon to open the Position tool The Position tool is automatically placed at the bottom of the Digital Stereoscope Workspace The Position tool gives you details on the coordinate system of the image or stereopair displayed in the Digital Stereoscope Workspace Geometric Properties Click this icon to show the geometric properties of the image displayed in the Workspace Geometric properties include projection camera and raster information About Stereo Analyst 7 Stereo Analyst Feature Toolbar Stereo Analyst Gl Table 2 Stereo Analyst Toolbar Continued Rotate Click this icon to create a target that enables you to rotate the image s displayed in the Digital Stereoscope Workspace You click to place a target in the image Then you adjust the position of the image using an axis al Left Buffer Click this icon to move the left image of a stereopair independently of the right image This option is not active when you have a block file bIk displayed m Right Buffer Click this icon to move the right image of a stereopair independently of the left image This option is not active when you have a block file blk
70. tour guides in this book This book contains tour guides that help you learn about different components of Stereo Analyst All of the tour guides were created using color anaglyph mode If you want your results to match those in the tour guides you should switch to color anaglyph mode before starting To do so you select Utility gt Stereo Analyst Options Stereo Mode Stereo Mode Color Anaglyph Stereo The following is a basic overview of what you can learn by following the tour guides provided in this book You do not need to have ERDAS IMAGINE installed on your system to use the tour guides In this tour guide you are going to create a nonoriented that is without map projection information digital stereo model DSM from two independent IMAGINE Image img files You can learn to use your mouse to manipulate the data resolution and to correct parallax In this tour guide you are going to use two images to create an LPS Project Manager block file blk To create it you must provide interior and exterior orientation information which correspond to the position of the camera as it captured the image This information is readily available when you purchase data from providers Tour Guide Examples xiii Checking the Accuracy of a DSM Measuring 3D Information Collecting and Editing 3D GIS Data Texturizing 3D Models E Documentation E Conventions Used in This Book Bold Type Mouse Operation
71. used to simultaneously create hundreds of DSMs in one step Additionally the block files can be immediately opened in Stereo Analyst and be used to select the DSM of choice Specifically the steps you are going to execute in this example include e Select and display the left and right images e Open the Create Stereo Model dialog e Enter projection information e Enter sensor model parameters e Save the block file e View the block file The data you are going to use in this example is of Los Angeles California The data is continuous 3 band data with an approximate ground resolution of 0 55 meters The scale of photography is 1 24 000 NOTE The data and imagery used in this tour guide are courtesy of HJW amp Associates Inc Oakland California Approximate completion time for this tour guide is 45 minutes WV You must have both Stereo Analyst and the example files installed to complete this tour guide NOTE This tour guide was created in color anaglyph mode If you want your results to match those in this tour guide set your stereo mode to color anaglyph by selecting Utility gt Stereo Analyst Options gt Stereo Mode gt Stereo Mode Color Anaglyph Stereo First you must launch Stereo Analyst For instructions on launching Stereo Analyst see Getting Started Once Stereo Analyst has been started and you have an empty Digital Stereoscope Workspace you are ready to begin Getting Started
72. your keyboard Double click the value in the Y field and type the value 4761174 72 then press Enter on your keyboard Double click the value in the Z field and type the value 247 24 then press Enter on your keyboard To change the appearance of the crosshair select Utility gt Stereo Analyst Options gt Cursor Display gt Cursor Shape There you can choose a crosshair best suited to your application Notice that as you are typing in coordinates the display is driving to the coordinates you specify In this example you are taken to the first check point position it is located at the intersection of two roof lines Stereo Analyst 7 Position the cursor over the intersection of the crosshair to see the specific point in the Left and Right monoscopic Views The cursor on the left and right images comprising the DSM should be centered over the same feature the intersection of the two roof lines While viewing in stereo visually interpret the location of the 3D floating cursor over the feature The X and Y position should be located at the intersection of the two roof lines The 3D cursor should be resting on the roof Use the Position Tool 137 Compute X and Y Coordinate Accuracy 1 Ifthe X and or Y position of the floating cursor is incorrect select the Enable Update option in the Position tool Adjust the coordinates in the Position tool by dragging the image so that the crosshair overlaps the i
73. 0 55 meters The scale of photography is 1 24 000 The images you use in this example do not have a map projection associated with them therefore the DSM you create is nonoriented NOTE The data and imagery used in this tour guide are courtesy of HJW amp Associates Inc Oakland California Approximate completion time for this tour guide is 1 hour You must have both Stereo Analyst and the example files installed to complete this tour guide NOTE This tour guide was created in color anaglyph mode If you want your results to match those in this tour guide set your stereo mode to color anaglyph by selecting Utility gt Stereo Analyst Options gt Stereo Mode gt Stereo Mode gt Color Anaglyph Stereo To launch Stereo Analyst you first launch ERDAS IMAGINE You may select ERDAS IMAGINE from the Start gt Programs menu or you may have created a shortcut to ERDAS IMAGINE on your desktop Launch ERDAS IMAGINE Click the Stereo Analyst icon on the ERDAS IMAGINE toolbar E Stereo Optionally you can use Microsoft Explorer to navigate to the following directory IMAGINE Bin NTx86 Double click hifi exe to start Stereo Analyst You can create a shortcut to the executable on your desktop if you wish Click Stereo Analyst on the Stereo Analyst dialog The Digital Stereoscope Workspace opens Getting Started 76 Main View you perform Overview you can see the Left and Right Views show
74. 00 0 072 0 096 0 15 0 3 0 51 6600 0 0792 0 1056 0 165 0 33 0 561 7200 0 0864 0 1152 0 18 0 36 0 612 7800 0 0936 0 1248 0 195 0 39 0 663 8400 0 1008 0 1344 0 21 0 42 0 714 9000 0 108 0 144 0 225 0 45 0 765 9600 0 1152 0 1536 0 24 0 48 0 816 10800 0 1296 0 1728 0 27 0 54 0 918 12000 0 144 0 192 0 3 0 6 1 02 15000 0 18 0 24 0 375 0 75 1 275 18000 0 216 0 288 0 45 0 9 1 53 24000 0 288 0 384 0 6 1 2 2 04 30000 0 36 0 48 0 75 1 5 2 55 40000 0 48 0 64 1 2 3 4 50000 0 6 0 8 1 25 2 5 4 25 60000 0 72 0 96 1 5 3 5 1 B W File Size MB 363 204 84 21 7 Color File Size MB 1089 612 252 63 21 Stereo Analyst Scanning Aerial Photography 39 Coordinate Systems The Ground Coverage column refers to the ground coverage per pixel Thus a 1 40000 scale black and white photograph scanned at 25 microns 1016 dpi has a ground coverage per pixel of 1 mx 1 m The resulting file size is approximately 85 MB assuming a square 9 x 9 inch photograph Conceptually photogrammetry involves establishing the relationship between the camera or sensor used to capture the imagery the imagery itself and the ground In order to understand and define this relationship each of the three variables associated with the relationship must be defined with respect to a coordinate space and coordinate system Pixel Coordinate System Stereo Analyst The file coordinates of a digital image are defined in a pixel coordinate system A pixel coord
75. 00 ore a a xci aa M List of Figures surreal A dX List of TableS 02 2k a e X d XR e S d c EO aca X Preface 4 40 ies maru ub ura doe de d ae a ERR a RI About This Manual erre xiii Example Data ren xiii Tour Guide Examples xiii Creating a Nonoriented DSM assassanin oo ooo xiii Creating a DSM from External Sources xiii Checking the Accuracy of a DSM lle xiv Measuring 3D Information eee xiv Collecting and Editing 3D GIS Data xiv Texturizing 3D Models llle xiv Documentation es xiv Conventions Used in This Book xiv Bold Type i s s e A xiv Mouse Operation leer xiv Paragraph Types llle xvi TCO lt lt on ous OR A ARA CE UR x Introduction to Stereo Analyst 3 Introduction err 3 About Stereo Analyst rn 4 Stereo Analyst Menu Bar eee ee eee 4 Stereo Analyst Toolbar oo coco moco 6 Stereo Analyst Feature Toolbar 0 o 8 Next 2 12 0491 A e a O ee 9 IDIMAGIA a s ck ue dk eed A da de dd A Introduction ee rorea rer enedi 11 Image Preparation for a GIS 13 Using Raw Photography llle 13 Geoprocessing Techniques ooo 15 Traditional Approaches 18 Example 1 oa ke Rae Sta od Rn n e
76. 000 8 477758 317729 4761553 735138 253 565267 0 000000 End ASCII File Example 262 The Stereo Analyst STP DSM Introduction Stereo Analyst supports the creation and display of oriented DSMs from external aerial triangulation data that is results from performing a bundle block adjustment Oriented DSMs contain sufficient sensor model and image information to define the relationship between the images in a stereopair the sensor and the ground As a result the left and right image comprising a stereopair can be displayed in stereo while also providing accurate real world 3D geographic information The Stereo Analyst STP file serves as an ASCII meta data file that contains all of the necessary information required to display a stereopair and also collect real world 3D coordinates in stereo It is important to note that the STP file contains post processed sensor model information The images and results from aerial triangulation that is interior and exterior orientation information are first transformed outside of Stereo Analyst to account for the variation in orientation and image XY position for the left and right images comprising a stereopair E Epipolar The transformation procedure is referred to as epipolar resampling Resampling The epipolar resampling procedure resamples the original left and right images using the results from aerial triangulation As a result new image coordinate positions are calc
77. 89 285 Projection name 265 Pushbroom 285 Pyramid layer 79 285 R Radial lens distortion 46 47 285 Raw stereopair 286 RDX file 241 Reference coordinate system 286 Reference plane 42 Relief exaggeration 288 Remove Segments icon 9 Rendering 286 Resampling mode 265 Reshape icon 9 Resolution 38 Revert to Original icon 6 Right Buffer icon 8 Right hand rule 42 286 RMS error 46 RMSE 38 286 Root Mean Square Error RMSE 38 46 286 Rotate icon 8 Rotate the DSM 88 Rotation angle mode 265 matrix 49 Rubber sheeting 16 286 S Save icon 6 Scanning resolutions 38 39 Scene 286 Screen digitizing 286 Select Element icon 9 Select icon Icons Select 8 Self calibration 23 286 Sensor 286 Sensor model 23 Shapefile 286 SI 286 Single frame orthorectification 287 Softcopy photogrammetry 33 Space forward intersection 52 intersection 287 resection 51 287 SPOT 287 Stereo 287 Stereo model 287 Stereo Analyst Stereo Pair Chooser 287 Stereo scene 287 Stereopair 287 Stereoscopic parallax 64 viewing 61 STP file average flying height 265 epipolar focal length 265 geometry 264 inner parameter first 265 inner parameter second 266 introductory line 264 outer parameter first 266 outer parameter second 266 output image file first 265 output image file second 266 output image number first 265 output image number second 266 projection name 265 resampling mode 265 rotation angle mode 265 unit X and Y 265 unit Z 265 Streamin
78. Analyst Next 110 Creating a DSM from External Sources Introduction This tour guide leads you through the process of creating a DSM using accurate sensor information The resulting output is an oriented DSM A DSM can be created and automatically oriented for immediate use in Stereo Analyst With it accurate real world 3D geographic information can be collected from imagery Using accurate sensor model information eliminates the process of manually orienting and adjusting the images to create a DSM as you did in the previous tour guide Creating a Nonoriented DSM Stereo Analyst uses sensor information to automatically rotate level and scale the two overlapping images to provide a clear DSM for comfortable stereo viewing Additionally Stereo Analyst can automatically place the 3D cursor on the terrain thereby eliminating the need for you to constantly adjust the height of the floating cursor The necessary information required to create a DSM can be obtained from the following sources e output from 3rd party photogrammetric systems e output from various data providers e output from IMAGINE OrthoMAX and other softcopy photogrammetric software packages To create a DSM in Stereo Analyst the following information is required e Projection spheroid and datum e Average flying height above ground level used to acquire the imagery e Rotation order three rotation angles that is Omega Phi and Kappa define the orienta
79. Apply Tile button 2 on the Tile Options dialog The image is tiled onto the selected faces Scaling the Tiles The texture you just tiled looks flattened and distorted Now you will use the Tile Options to rescale the tiles to their correct proportions 1 Select the right rear face of the model 2 Click the Reset Tile Vertically button This optimizes the tile for vertical or near vertical surfaces such as walls 3 Click the Locked icon a to unlock the aspect ratio This allows you to scale the X and Y directions separately 4 Drag the Scale Y Direction thumbwheel left until the tile appears to be stretched to fit the entire height if the building 5 Adjust the Move Y Direction thumbwheel until the tile is centered on the model face 6 Adjust the Scale X Direction and Move X Direction thumbwheels until the you have three tiles across the selected face Stereo Analyst Tiling a Texture 234 Add a new Image to the Library Stereo Analyst The tiled texture is approximately the same scale as the mapped texture You will need to perform these last steps several times to get a good approximation Repeat these steps for each of the remaining four faces Hoa m m 8H ZAS a miit EEE rd mmu Now that you have tiled the walls of the building it is time to tile the roof First you will need to add a new Image Class and Image to the Tile Library Enter the Tile Options mode by clicking the Til
80. Clair DE Select Buildings and Related Features Stereo Analyst 1 Clickthe Category dropdown list and select Buildings and Related Features Create a New Feature Project 173 Feature Project Chaves Festa Clases Stereo Model Click the dropdown list to Sale easet ho include in ous pemet select the feature Category Lau EEUTETLITTUTTCENEENNN Eum quu e gen n mi Bakir 2 Then click the check boxes dapes Buldeg next to the classes you want i mm r NE fuking Mu ples Canpgeund error 2 Usethe scroll bar at the right of the features to see all of the different classes included in this category 3 Scroll back up and click the checkbox next to Building 1 That feature is added to the Selected Classes list LZ mur i Devis Feature Clanes Stereo Model a ro Classes are listed Cages Bukdren arl Fired Feste l here as you select them 5 aa c gen n I Baking 2 dapes Ball Y ZH IU Dacia 4 Bull Upa Copan Cerretery Select Roads and Related Features 1 Click the Category dropdown list again and choose Roads and Related Features 2 Click the checkbox next to the Light Duty Road feature This feature is also added to the Selected Classes list Stereo Analyst Create a New Feature Project 174 Each category has icons to represent the different class LUE mur i Geva Feature Claes ineo Model Ekel lancer his rotlada mins peon Caig
81. Digital Stereoscope Workspace Save Click this icon to save changes you have made ad to your feature projects Choose Click this icon to open the Stereo Pair Chooser Stereopair dialog From there you can select other stereopairs to view in the Digital Stereoscope Workspace Clear the Click this icon to clear the Digital Stereoscope amp Stereo View Workspace of images and any features you have collected Image Click this icon to obtain information about the top raster layer displayed in the Digital Stereoscope Workspace Information includes cell size rows and columns and other image details Fit Scene Click this icon to fit the entire stereo scene in the Main View If your default is set to show both overlapping and nonoverlapping areas both are displayed in the stereo view You can use Mask Out Non Stereo Regions in the Stereo View Options category of the Options dialog to see only those areas that overlap Revert to Original Click this icon to return the scene back to its original resolution and rotation Zoom 1 1 Click this icon to adjust the scene to a 1 1 screen pixel to image pixel resolution Cursor Tracking Click this icon to open the Left View and the Right View These small views allow you to see the left and right images of the stereopairs independently Stereo Analyst About Stereo Analyst 6 Stereo Analyst 3D Feature View Table 2 Stereo Analyst Toolbar Con
82. Digital Stereoscope Workspace adjusts to accommodate them Next check the attributes of the final feature you collected the woods bordering the river 1 Click the Attribute icon il next to the Woods feature class The attribute table for the woods feature opens Pia AE em Pon Bate a Se El Re GOO amp P COL Ii 123 L oH r tia ag If you only want to view the Woods attributes close the Building 1 attribute table by clicking here 2 Use the scroll bar to see all of the attributes for the Woods feature class Like with the Building 1 feature class you can also perform analysis on the Woods feature class by accessing the Row Options and Column Options menus You can even export the data in the attribute tables to a data file dat 3 Click the Clear View icon amp The following dialog opens Stereo Analyst Check Attributes 219 Click Yes to save the o a Beane il deta temes i features you collected dept letra gg e 4 Click Yes to save your feature project y If you edit feature class properties in a feature project the next time you save the project you are prompted as to whether or not you want to save the display properties and attributes changes to the global feature class If you select Yes the global feature class is permanently altered If you select No then the display properties and attributes changes are only saved to the feature class in the current project It is highly rec
83. Fisadi ard Related Features Seno Hey Croata Dato esae Clr Urost Remove a ce Bep Create a Custom Feature Class Stereo Analyst You are also going to be digitizing a sidewalk area in this exercise Next you are going to create a custom feature class just for sidewalks Click the Create Custom Feature Class button at the bottom of the Feature Classes tab The Create Custom Class dialog opens on the General tab Create Curio Chase You start creating a custom class in the General tab Type the name of the new feature class here Type a name for the fcl file here it can be the same as the feature class name above Select the appropriate Category from the dropdown list 2 Click in the Feature Class window and type Sidewalk Next you need to create the fcl file The fcl file is a feature class file that holds all the information for a given feature category such as the icon associated with it and attribute information Create a New Feature Project 175 3 Click in the Filename window and type sidewalk then press Enter on your keyboard The fcl extension is automatically added Next you need to select which category you want your new feature associated with 4 Click the Category dropdown list and select Roads and Related Features If you like you can even assign an icon to the feature class To do so click the Use icon for feature class checkbox and then select the a
84. GE NO FIRST 12 INNER PAR FIRST 64 768081403 0 050017079 0 0 108 173757261 0 0 0 050017079 OUTER PAR FIRST 426319 7210 3717179 8370 7619 8140 0 0000 0 0659 147 3785 OUTPUT IMAGE FILE SECOND c3rgb50ep img OUTPUT IMAGE NO SECOND 13 INNER PAR SECOND 115 236231809 0 050017079 0 0 108 173757261 0 0 0 050017079 OUTER PAR SECOND 424013 4810 3718655 9580 7617 1600 0 0000 0 0659 147 3785 Stereo Analyst STP File Example 267 Stereo Analyst STP File Example 268 References E Introduction E Works Stereo Analyst This appendix includes a list of works you may want to read for further information as well as works cited in this document Ackermann F 1983 High precision digital image correlation Proceedings of 39th Photogrammetric Week Institute of Photogrammetry University of Stuttgart pp 231 243 Agouris P and T Schenk 1996 Automated Aerotriangulation Using Multiple Image Multipoint Matching Photogrammetric Engineering and Remote Sensing 62 6 703 710 American Society of Photogrammetry 1980 Photogrammetric Engineering and Remote Sensing XLVI 10 1249 Bauer H and J M ller 1972 Height accuracy of blocks and bundle block adjustment with additional parameters ISPRS 12th Congress Ottawa Ebner H 1976 Self calibrating block adjustment Bildmessung und Luftbildwesen Vol 4 El Hakin S F 1984 A step by step strategy for gross
85. GIS Using Raw Photography Stereo Analyst Figure 1 Accurate 3D Geographic Information Extracted from Imagery This section describes the various techniques used to prepare imagery for a GIS By understanding the processes and techniques associated with preparing and extracting geographic information from imagery we can identify some of the problem issues and provide the complete solution for collecting 3D geographic information The following three examples describe the common practices used for the collection of geographic information from raw photographs and imagery Raw imagery includes scanned hardcopy photography digital camera imagery videography or satellite imagery that has not been processed to establish a geometric relationship between the imagery and the Earth In this case the images are not referenced to a geographic projection or coordinate system Image Preparation for a GIS 13 Example 1 Collecting Geographic Information from Hardcopy Photography Hardcopy photographs are widely used by professionals in several industries as one of the primary sources of geographic information Foresters geologists soil scientists engineers environmentalists and urban planners routinely collect geographic information directly from hardcopy photographs The hardcopy photographs are commonly used during fieldwork and research As a result the hardcopy photographs are a valuable source of information For the interpretati
86. Image and Data Acquisition 36 The photographs from several flight paths can be combined to form a block of photographs A block of photographs consists of a number of parallel strips normally with a sidelap of 20 30 A regular block of photos is commonly a rectangular block in which the number of photos in each strip is the same Figure 12 shows a block of 5 x 2 photographs In cases where a nonlinear feature is being mapped for example a river photographic blocks are frequently irregular Figure 13 illustrates two overlapping images Figure 12 A Regular Rectangular Block of Aerial Photos 60 overlap EM Flying direction Strip 2 Me block 20 30 sidelap Strip 1 Ej Scanning Aerial Photography Photogrammetric Scanners Stereo Analyst Figure 13 Overlapping Images fs Area of overlap Photogrammetric scanners are special devices capable of high image quality and excellent positional accuracy Use of this type of scanner results in geometric accuracies similar to traditional analog and analytical photogrammetric instruments These scanners are necessary for digital photogrammetric applications that have high accuracy requirements Scanning Aerial Photography 37 Desktop Scanners Scanning Resolutions Stereo Analyst These units usually scan only film because film i
87. Index file 241 stp Stereopair 275 X AX X Numerics 2D 275 2D affine transformation 45 3D 275 3D Extend icon 9 3D floating cursor 69 275 3D geographic imaging 20 3D Measure Tool icon 7 3D shapefile 275 A Accuracy check 129 Active tool 276 Add Element icon 9 Adjusted stereopair 276 Aerial photographs 34 276 Aerial triangulation AT 53 276 Affine transformation 276 Affine transformation coefficients 112 Air base 276 Airborne GPS 53 58 276 Airborne INS 58 276 American Standard Code for Information In terchange 255 276 Anaglyph 276 Analog photogrammetry 32 276 Analytical photogrammetry 32 276 Anti aliasing 277 ASCII 255 AT 53 Attribute 277 Attribute table 277 Attribution 277 Automated DTM extraction 24 Automated Terrain Following 70 Autopan buffer 156 208 Average flying height 120 265 Stereo Analyst B b h 280 Base height ratio 277 Bilinear interpolation 265 Block file 277 Block triangulation 53 277 Box Feature icon 8 Breaklines 277 Bucket 277 Bundle block adjustment 24 53 277 definition 53 C Cache 278 CAD 278 Calibration certificate report 23 112 278 CCD 278 Charge coupled device 278 Choose Stereopair icon 6 Clear View icon 6 Collect features 171 Collinearity 278 Collinearity condition 50 278 Collinearity equations 55 Computer aided design 278 Control point extension 278 Convergence value 58 Coordinate system 40 278 ground space 40 image spa
88. Move the mouse amp gt in these directions 3 Continue to roam and zoom throughout the image to familiarize yourself with the mouse motions You can also roam throughout the image by selecting the crosshair in the OverView and moving it Check Quick Menu Stereo Analyst has tools that allow you to change the brightness and Options contrast of images as they are displayed in the Digital Stereoscope Workspace 1 Navigate to an area that interests you 2 Zoom in to see the details of the area Stereo Analyst Adjust Display Resolution 83 3 Click the right mouse button a MER the right mouse button The Quick Menu opens Quick Hera Ford Cuorpor PE Some To do Point to the Marvigation Help Left Image option Berea Analyt Dina Lirado Estas di 4 Move your mouse over the Left Image option on the Quick Menu The options you can apply to the Left Image display Click the Band Dan Sal Combinations option Hisl ing am Ende Sanidad Deevishion reir Vere ai Conde gl ErighiressjCanes ask Pecera Contrat Bidire Lami esporte ve a pad Stereo Analyst Adjust Display Resolution 84 These options are also available under Raster gt Right Image when you have a right image displayed in the workspace Check Band Combinations 1 Click on the first option Band Combinations The following dialog opens sE Cer aL The number of layers in the image is reported he
89. N lees 258 ASCII File Example c r 258 The Stereo Analyst STP DSM 263 Introduction erre 263 Epipolar Resampling 263 Coplanarity Condition leen 263 STP File Characteristics 264 STP File Example ccrns 266 RETEFENCES i cce ego a o6 s WOO WO E C CE A Roue woo XX a 269 GIOSSANY r PTPPA Introduction nnn onm nnn n 275 N meriCS ios dace he bed ade rad 275 Terms iux e ee ee ee a ees ee es ci ee a 276 Ni sau eo E a a a we ee Stereo Analyst Table of Contents viii List of Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 Figure 28 Figure 29 Figure 30 Figure 31 Figure 32 Figure 33 Figure 34 Figure 35 Figure 36 Figure 37 Figure 38 Figure 39 Figure 40 Figure 41 Figure 42 Accurate 3D Geographic Information Extracted from Imagery 13 Spatial and Nonspatial Information for Local Government Applications 16 3D Information for GIS Analysis 4 4 4 20 Accurate 3D Buildings Extracted using Stereo Analyst 26 Use of 3D Geogr
90. OrthoBASE Block File blk 3 Navigate to the directory in which you saved la create blk 4 Click to select the file then click OK in the Select Layer To Open dialog The block file you created la create blk displays in the Digital Stereoscope Workspace The block file DSM is composed ofla left img and la right img as shown here Gott 40 RT eRe weep CIL Ul Em L 580g 5 Adjustthe x parallax as necessary to improve the appearance of the DSM Stereo Analyst Open the Block File 126 Next Stereo Analyst The two images comprising the DSM have been superimposed Using the sensor model information the difference between the left and right image orientation and position has been considered Thus the images do not need to be rotated scaled leveled or adjusted for y parallax Stereo Analyst has automatically performed this task Prior to viewing the DSM in 3D the images must be adjusted so as to minimize the x parallax in the model An alternative approach to improving the alignment and eliminating the need to adjust the x parallax to obtain a clear DSM includes entering a tie point position while creating a block file The left and right image position of a tie point can be input in the Tie Point tab of the Create Stereo Model dialog The left and right image position for the tie point must reflect the same feature on the surface of the Earth The values must be in pixels NOTE Leica Geosystems is curre
91. Problem B Geographic Imaging Stereo Analyst Ground surveying techniques are accurate but are labor intensive costly and time consuming even with new GPS technology Also additional work is required by you to merge and link the 3D information with the GIS The process of geolinking and merging the 3D information with the GIS may introduce additional errors to your GIS The next example involves automated digital elevation model DEM extraction Using two overlapping images a regular grid of elevation points or a dispersed number of 3D mass points that is triangulated irregular network TIN can be automatically extracted from imagery You are then required to merge the resulting DTM with the geographic information contained in the GIS You are restricted to the collection of point elevation information For example using this approach the slope of a line or the 3D position of a road cannot be extracted Similarly a polygon of a building cannot be directly collected Many times post editing is required to ensure the accuracy and reliability of the elevation sources Automated DEM extraction consists of just one required step to create the elevation or 3D information source Additional steps of DTM interpolation and editing are required not to mention the additional process of merging the information with your GIS This example involves outsourcing photogrammetric feature collection and data capture to photogrammetric service
92. Stereo Analyst e User s Guide when it has to be right Leica Geosystems Copyright 2006 Leica Geosystems Geospatial Imaging LLC All rights reserved Printed in the United States of America The information contained in this document is the exclusive property of Leica Geosystems Geospatial Imaging LLC This work is protected under United States copyright law and other international copyright treaties and conventions No part of this work may be reproduced or transmitted in any form or by any means electronic or mechanical including photocopying and recording or by any information storage or retrieval system except as expressly permitted in writing by Leica Geosystems Geospatial Imaging LLC All requests should be sent to the attention of Manager of Technical Documentation Leica Geosystems Geospatial Imaging LLC 5051 Peachtree Corners Circle Suite 100 Norcross GA 30092 USA The information contained in this document is subject to change without notice Government Reserved Rights MrSID technology incorporated in the Software was developed in part through a project at the Los Alamos National Laboratory funded by the U S Government managed under contract by the University of California University and is under exclusive commercial license to LizardTech Inc It is used under license from LizardTech MrSID is protected by U S Patent No 5 710 835 Foreign patents pending The U S Government and the University have reserved
93. The red designates the left image of the DSM uL S Pian Tr HIP ih ee DM ATL Pha lode 1 T Start digitizing the river in this area Select the River Feature and Digitize 1 From the Feature Class Palette click to select the Per River icon E Pe Peers 2 From the feature toolbar select the Stream Digitizing tool gl Stereo Analyst Collect a River Feature 207 H Collect a Forest Feature Stereo Analyst In order for the DSM to readjust its position in the display as you approach the extent of the visible space in the Main View release the left mouse button Position the cursor at the extent of the visible area to activate the autopan buffer Stereo Analyst recognizes when your cursor is in the autopan buffer and adjusts the stereopair in the view accordingly You can then continue to use the Stream Digitizing tool Move your mouse into the display area and position the cursor at the edge of the river Adjust the cursor elevation by rolling the mouse wheel until it rests on the bank NOTE You may find this easier if you zoom into the image Click to digitize the first vertex on the side of the river bordering the subdivision Hold down the left mouse button and drag the mouse to digitize northward along the river bank Double click to terminate collection of the river at the edge of the stereopair Adjust the display so that you can see the entire river section you digitized The river edge feature is hi
94. a calibration information that is focal length principal point 3D Information from Stereo Models 70 This information is collectively referred to as sensor model information Sensor model information is determined using bundle block triangulation techniques When sensor model information is applied to a stereopair a DSM can be created Using 3D space intersection techniques 3D coordinate information can be derived from a stereopair Figure 35 illustrates the use of space intersection techniques for the collection of 3D point information from a stereopair 3D coordinate information can be derived from two overlapping images when sensor model information is known Figure 35 Space Intersection In Figure 35 Ly and L5 represent the position and orientation information associated with the left and right images respectively Once the 3D floating cursor has been adjusted so that it rests on the ground the image positions of ground point A on the left and right images are known In order to obtain accurate 3D coordinate information it is important that the 3D floating cursor rests on the feature of interest If the 3D floating cursor rests on the feature of interest the corresponding image position on the left and right images reflects the same feature Stereo Analyst 3D Information from Stereo Models 71 Figure 36 Stereo Model in Stereo and Mono SL zu Save RC EIAN O tae GUL LEEMETS nBrctisanam Stereo vi
95. a clear 3D stereo view 2 In the 3D Measure tool click to select the Polygon tool v 3 Position your cursor at one corner of the ice rink adjust the 3D floating cursor until it rests on the top of the ice rink edge NOTE The optimum zoom rate for measuring information in this portion of the image is approximately 1 3 You can enter this value into the Position tool 4 Click to digitize the first vertex 5 Continue to digitize around the perimeter of the ice rink adjusting the 3D floating cursor as necessary 6 Once you have finished digitizing the ice rink double click to close the polygon Evaluate Results The measurements are reported in the text field of the 3D Measure tool JD Measure Tag a ox garra ow F olggon 1 Area EM crea Langh HI HA erae Z dilaveree DEE atiii Z iar DAD EI H meten PT FFAA AO mederi 245 IDE p Pi ATI TAEDE C080 TM meters 243 HCIT eter Deka e 01157 pelea ope 011165 peau 355 3527 degnees PI ATTORI LEE TTE TARTE mede 2405 HL macer Deka E 00055 peta Slope D OCT pus 33 5828 depor PA AN AA AAA ESA mederi 245 TT necem This feature is identified as a polygon NOTE Your results may differ from those presented here 1 Use the scroll bar to see the first line of data associated with the polyline you just digitized Polygon 1 Stereo Analyst Take 3D Measurements 163 Polygon 1 Area 0 3248 acres Length 149 3495 meters This means that the area of the ice rink is approxima
96. ab 4 Using the following table type the six exterior orientation parameters into the Exterior tab Stereo Analyst Open the Create Stereo Model Dialog Table 8 Exterior Orientation Parameters for Frame 2 la_right img position rotation X 382484 8340 Omega 0 1419 3762868 9323 Phi 0 4291 Z 3928 6787 Kappa 91 7508 When you have finished the Frame 2 tab of the Create Stereo Model dialog looks like the following Creale Seres Model The name of the second image displays here Viens Aire Types Carra Dort Exterior and Interior information specific to the second image is input here Apply the Information 1 In the Create Stereo Model dialog click the Apply button Once the Apply button has been selected all of the image sensor model information is saved to the block file 2 Click the Close button to dismiss the Create Stereo Model dialog 3 In the Digital Stereoscope Workspace click the Clear Viewer icon gl Stereo Analyst Open the Create Stereo Model Dialog 125 Open the Block To view the DSM you need to open the block file that contains the File sensor model information WV For the remainder of the tour guide you need either red blue glasses or stereo glasses that work in conjunction with an emitter 1 Click the Open icon ri in the Digital Stereoscope Workspace 2 Inthe Select Layer To Open dialog click the Files of type dropdown list and select IMAGINE
97. an be exported as descriptive ASCII files for use in other mapping and CAD packages such as MicroStation AutoCAD and TerraModel The Stereo Analyst ASCII file can be broken down into the following categories introductory text number of classes shape class number shape class 2 and shape class n The introductory text introduces the Stereo Analyst ASCII file This value states the number of feature classes used and defined within the Stereo Analyst feature project Shape Class Number has additional categories FCODE that is Feature Code is the primary index used to define a unique feature class Each feature class in Stereo Analyst has a unique feature code The shape type defines the type of feature that has been collected This includes point and multiple point features for example 3D POINT shape type polygon features for example 3D POLYGON shape type and polyline features for example 3D ARC shape type Number of Attributes Stereo Analyst The number of attributes is defined within the Feature Attributes tab of the Feature Project dialog The number of attributes includes the default Stereo Analyst attributes for a given feature type plus the attributes you define Each feature type has the following attribute fields e Point and multiple point features have a default Feature ID FID and Avg Z attribute field e Polyline features have a default FID Length and AvgZ attribute field ASCII Categor
98. and drag line segments and vertices that make up the forest feature to move them to a new location 6 Click the Reshape icon again to deselect it 7 Click outside the forest feature to deselect it 8 When you are finished click the Zoom to Full Extent icon ei Collect a Forest Feature Next you can learn how to create features that share boundaries and Parking Lot Select a Different Stereo Model The features you are going to collect are located in a different DSM within the western accuracy blk file 1 Click the Stereo Pair Chooser icon i f Stereo Analyst Collect a Forest Feature 210 The Stereo Pair Chooser opens Here you can rapidly select another DSM to view in the Digital Stereoscope Workspace 2 Click in the ID column and select 2 This corresponds to the DSM consisting of the images 252 img and 253 img 3 Click Apply then Close The new DSM displays in the Digital Stereoscope Workspace Open the Position Tool 1 Click the Position tool icon in the toolbar of the Digital Stereoscope Workspace The Digital Stereoscope Workspace adjusts to accommodate the Position tool 2 In the Position tool type the value 477052 in the X field then press Enter on your keyboard 3 Type 4761603 in the Y field then press Enter 4 Type 242 2148 in the Z field then press Enter 5 Type 0 1 in the Zoom field then press Enter The following forest displays in the Digital Stereoscope Workspace It is adjacent
99. ane Two types of radial lens distortion exist radial and tangential lens distortion Lens distortion occurs when light rays passing through the lens are bent thereby changing directions and intersecting the image plane at positions deviant from the norm Figure 19 illustrates the difference between radial and tangential lens distortion Figure 19 Radial vs Tangential Lens Distortion ATAAt radial distance r o z gt x Interior Orientation 46 E Exterior Orientation Stereo Analyst Radial lens distortion causes imaged points to be distorted along radial lines from the principal point o The effect of radial lens distortion is represented as Ar Radial lens distortion is also commonly referred to as symmetric lens distortion Tangential lens distortion occurs at right angles to the radial lines from the principal point The effect of tangential lens distortion is represented as At Because tangential lens distortion is much smaller in magnitude than radial lens distortion it is considered negligible The effects of lens distortion are commonly determined in a laboratory during the camera calibration procedure The effects of radial lens distortion throughout an image can be approximated using a polynomial The following polynomial is used to determine coefficients associated with radial lens distortion Ar kor kjr k r In the equation above Ar represents the radial di
100. ape POINT e Point Display Attributes and The point display attributes characterize the color used to display the point feature in Stereo Analyst e Point Feature Attributes The point feature attributes define the attributes to be used for the specific point feature class The following information is used to characterize each point feature attribute Stereo Analyst Feature Classes 245 Polyline Feature Class Stereo Analyst type of point feature attribute STRING INTERGER FLOAT DATE maximum width of attribute display and number of decimal places used to display the attribute The following feature class provides an example of a Horizontal Control point feature class FeatureClass iHoriz Control Category iHorizontal Control IconFile 11 bmp1 FeatureCode 1000 FeatureShape POINTN PointDrawAttributes Color 1 00 0 00 0 00 FeatureAttributes iFID INTEGER 5 0 iAvg Zi FLOAT 12 2 A Stereo Analyst feature class file fcl for a polyline feature contains the following information e Feature Class Name See General Information e Feature Class Category e Icon File e Feature Code e Feature Shape The feature shape describes the shape POLYLINE e Polyline Display Attributes and The polyline display attributes characterize the color and line width used to display the polyline feature in Stereo Analyst e Polyline Feature Attributes The p
101. aphic Imaging Techniques in Forestry 27 Topography i s cux qox a A A a Re ee SR do Eod 31 Analog Stereo Plotter s i sre a gant daig eo oe a oon om n 32 LPS Project Manager Point Measurement Tool Interface 33 Satellite 29 x 3eR3co Rc93 3 oy exc Y a X X dor wo Seed 34 Exposure Station se erada eae 4 xod Hew eee bee OE ES ee ds 36 Exposure Stations Along a Flight Path o 36 A Regular Rectangular Block of Aerial Photos lens 37 Overlapping Images e a ohh oa y o n on nn 37 Pixel Coordinates and Image Coordinates llle sen 40 Image Space and Ground Space Coordinate System s n 41 Terrestrial Photography 4 es 43 Internal Geometry lee sees ehh ohh ooh n on n n nn 44 Pixel Coordinate System vs Image Space Coordinate System 45 Radial vs Tangential Lens Distortion ee 4 46 Elements of Exterior Orientation 0 4 4 0 4 48 Omega Phi and KapDa o ele s 48 Space Forward Intersection lel hens 52 Photogrammetric Block Configuration 2 e e e 2 o 54 Two Overlapping Photos lee horns 62 Stereo VIeW s a xx eG a A a Dak wx m Gee Ee nme de es d 63 3D Shapefile Collected in Stereo Analyst 0 o a 64 Left and Right Images of a Stereopair o
102. arts 1 Part 0 Number of Points 1 0 477831 987510 4761599 411265 250 306677 0 000000 Shape 4 Attribute Values 0 5 000000 1 250 220000 Number of Parts 1 Part 0 Number of Points 1 0 477923 232009 4761651 720452 250 219824 0 000000 Shape 5 Attribute Values 0 6 000000 1 252 400000 Number of Parts 1 Part 0 Number of Points 1 0 477692 491579 4761488 963133 252 403413 ASCII File Example 261 Stereo Analyst 0 000000 Shape 6 Attribute Values 0 7 000000 1 250 040000 Number of Parts 1 Part 0 Number of Points 1 0 477682 114596 4761405 622751 250 044994 0 000000 Shape Class 10 iwoods FCode 7000 Shape Type 3D POLYGON Number of Attributes 4 0 type NUMERIC width 5 numdecs 0 name iFIDi 1 type FLOAT width 12 numdecs 2 name iAreai 2 type FLOAT width 12 numdecs 2 name iPerimeteri 3 type FLOAT width 12 numdecs 2 name 1Avg_Z1 Number of Shapes 1 Shape 0 Attribute Values 0 1 000000 1 8390 510000 2 413 790000 3 248 160000 Number of Parts 1 Part 0 Number of Points 9 0 477758 317729 4761553 735138 253 565267 0 000000 1 477754 754678 4761532 416856 252 219727 0 000000 2 477760 762991 4761502 755170 252 358410 0 000000 3 477804 215829 4761494 510509 249 930082 0 000000 4 477810 416840 4761487 257458 250 078908 0 000000 5 477882 250052 4761475 361479 243 391896 0 000000 6 477923 795964 4761499 612660 241 411015 0 000000 7 477915 573326 4761525 874234 242 352411 0 000
103. as the Reshape tool are available to you See also Disabled tool EOSAT See Earth Observation Satellite Company Ephemeris Data contained in the header of the data file of a SPOT scene provides information about the recording of the data and the satellite orbit Epipolar stereopair A stereopair without y parallax Exposure station During image acquisition each point in the flight path at which the camera exposes the film Exterior orientation All images of a block of aerial photographs in the ground coordinate system are computed during photogrammetric triangulation using a limited number of points with known coordinates The exterior orientation of an image consists of the exposure station and the camera attitude at the moment of image capture Exterior orientation parameters The ground coordinates of the perspective center in a specified map projection and three rotation angles around the coordinate axes Eye base to height ratio b h The eyebase is the distance between a person s eyes The height is the distance between the eyes and the image datum When two images of a stereopair are adjusted in the X and Y direction the b h ratio is also changed You change the X and Y positions to compensate for parallax in the images Feature collection The process of identifying delineating and labeling various types of natural and human made phenomena from remotely sensed images Feature collection mode One of the two featu
104. ass the number of shapes would be 20 Shape Number The shape number value states the shape that is described in the following description Stereo Analyst ASCII Categories 256 Attribute Values The attribute value for a given attribute is a series of alpha numeric characters which has been automatically computed by Stereo Analyst for example AvgZ or input by you for example the address of shape 354 is 741 Pacific Ave The following is an example of attribute values 0 2 0 1 3001 5 2 220 57 3 256 22 In this example the 0 attribute is FID and the value is 2 0 The 1 attribute is Area and the value is 3001 5 The 2 attribute is Perimeter and the value is 220 57 The 3 attribute is Avg Z and the value is 256 22 Stereo Analyst Number of Parts This value indicates the number of parts or feature elements associated with a given feature A Part is also referred to as a feature element For example a building feature can have several feature elements associated with it A feature element is a feature for example point polyline polygon having an association with an existing feature Therefore when you select a feature within Stereo Analyst all of the elements if they are available associated with the feature are selected Part Number This value indicates which part is described in the following portion of the ASCII file Number of Points The number of points is the number of vertices associated with a f
105. ate system directs the z axis toward the imaged object and the y axis directed North up The image x axis is similar to that used in aerial applications The X Y and Z coordinates define the position of the perspective center as it existed atthe time of image capture The ground coordinates of ground point A Xa Ya and Z4 are defined within the ground space coordinate system Xg Yc and Zo With this definition three rotation angles o Omega Phi and x Kappa define the orientation of the image You can also use the ground X Y Z coordinate system to directly define GCPs Thus GCPs do not need to be transformed Then the definition of rotation angles 9 and are different as shown in Figure 16 Stereo Analyst Scanning Aerial Photography 43 Interior Orientation Principal Point and Focal Length Stereo Analyst Interior orientation defines the internal geometry of a camera or sensor as it existed at the time of image capture The variables associated with image space are obtained during the process of defining interior orientation Interior orientation is primarily used to transform the image pixel coordinate system or other image coordinate measurement systems to the image space coordinate system Figure 17 illustrates the variables associated with the internal geometry of an image captured from an aerial camera where o represents the principal point and a represents an image point Figure 17
106. ation is used to characterize each polygon feature attribute type of polygon feature attribute STRING INTERGER FLOAT DATE maximum width of attribute display and number of decimal places used to display the attribute Stereo Analyst Feature Classes 247 The following feature class provides an example of a Building 1 polygon feature class FeatureClass Building 11 Category iBuildings and Related Featuresi IconFile 181 bmp1 FeatureCode 12000 FeatureShape POLYGON PolygonDrawAttributes DrawFilled FillColor 0 00 0 00 0 00 Opacity 40 DrawBorder BorderColor 1 00 1 00 1 00 BorderWidth 1 FeatureAttributes iFIDiINTEGER50 iAreaiFLOAT122 iPerimeteri FLOAT122 iAvg_ZiFLOAT122 Default Stereo The default Stereo Analyst feature classes can be located within the Analyst Feature lt IMAGINE_HOME gt etc FeatureClasses directory When a feature project is created the feature classes you select are copied into the Classes feature project directory The addition of new feature attribute information does not affect the template feature class files It is highly recommended that the original feature class files not be edited or modified If you edit feature class properties in a feature project the next time you save the project you are prompted as to whether or not you want to save the display properties and attributes changes to the global feature class If y
107. ature Class Palette The feature class name is also used as the name for the output 3D Shapefile Stereo Analyst Feature Classes 244 Point Feature Class Stereo Analyst e Feature Class Category Stereo Analyst provides a default set of feature class categories Feature class categories contain a series of feature classes A feature class category can be created within the General tab of the Create Custom Class dialog e Icon File The icon file is a bitmap bmp file used to represent the feature class in the feature class palette The icon file must be a bitmap file e Feature Code The feature code is a unique numeric value used to identify and index a feature class e Feature Display Attributes The feature display attributes characterize how a given feature class displays once it has been collected e Feature Attributes The feature attributes define the attributes to be used for the specific feature class The following information is used to characterize each feature attribute type of feature attribute STRING INTEGER FLOAT DATE maximum width of attribute display and number of decimal places used to display each feature attribute A Stereo Analyst feature class file fcl for a point feature contains the following information e Feature Class Name ai See General Information e Feature Class Category e Icon File e Feature Code e Feature Shape The feature shape describes the sh
108. atures contained in a DSM With the stereopair 252 img and 253 img displayed in the Digital Stereoscope Workspace click the 3D Measure tool icon e The 3D Measure tool occupies the bottom portion of the Digital Stereoscope Workspace Nm lum Hiara gJ B 2 Mas ID HIPPIE RTT DE EI PR Rad etd Tools you open display at the bottom of the Digital Stereoscope Workspace Stereo Analyst Since you have used the Position tool in the previous tour guide you are familiar with entering 3D coordinates into it to drive to certain locations in the DSM Next you can use the Position tool to drive to areas in the stereopair and then take measurements with the 3D Measure tool Take 3D Measurements 152 2 Click the Position tool icon The Position tool occupies the lower half of the Digital Stereoscope Workspace along with the 3D Measure tool If you would rather have the tools display horizontally click the a4 icon located in the upper right corner of each tool o o ui Du Eo lt DATO amp mm CUL Tis Fae ks A as Dima luem P oW Sec Dur Edu oe s jm Lain ae Mer us am Wi E 3 Dm m E i 2 BAI STR AILES A A a dde E 0 gt e The Digital Stereoscope Workspace adjusts to accommodate both tools You may find the terrain following cursor helpful in completing this exercise Stereo Analyst Take 3D Measurements 153
109. ause the polygon no longer appears filled and the vertices that create the polygon are highlighted If you cannot select the polygon first click the Select icon amp located on the feature toolbar Your building should look like the one pictured in the following illustration Stereo Analyst Collect Building Features 187 You can see individual vertices that make up the polygon when the building is selected 5 Click to select the 3D Polygon Extend tool from the feature toolbar 6 Click to select any one of the vertices that makes up the roofline Stereo Analyst creates a 3D footprint of the roof which touches the ground It appears in the Main View as a duplicate of the roof line you digitized but slightly offset Notice the individual vertices this indicates that the polygon feature is selected 7 Left click outside the 3D polygon to deselect it The polygon changes appearance to reflect all of the vertices you digitized to capture the roofline It now appears as a 3D feature 8 Zoom in or out until you can comfortably see the 3D polygon in the Main View Stereo Analyst Collect Building Features 188 m buo cum emm ee cb sw NJ O Ree O wedl ga to a Lt r1 Ea At each vertex location a line extends to the ground The polygon is now 3D and has the added Z or elevation component 9 Click the Zoom to Image Resolution icon gl Collect the Second Again practice using the 3D Polygon Extend
110. ce 40 Coplanarity condition 263 278 Copy icon 8 Correlate 278 Create custom feature class 175 Create DSM 111 Create Stereo Model icon 7 Cursor Tracking icon 6 Custom feature class 175 Cut icon 8 D Datum 278 dBase 241 Degrees of freedom 56 278 Delta 278 Delta Z 147 278 DEM 278 279 Desktop scanners 38 Digital elevation model 279 Digital orthophoto 279 Digital photogrammetric workstations 279 Digital photogrammetry 21 33 279 Digital stereo model 279 Index 291 Digital terrain model 279 Direction of flight 35 279 Disabled tool 279 DLL 4 279 DPW 279 DSM creation 111 DTM 279 Dynamically Loaded Library DLL 4 279 E Earth Observation Satellite Company 279 Edit features 171 Elements of exterior orientation 47 279 Ellipsoid 279 Enabled tool 280 EOSAT 279 280 Ephemeris 279 280 Epipolar focal length 265 line 264 plane 264 resampling 263 resampling on the fly 68 stereopair 280 Exposure station 36 280 Exterior orientation 47 280 Exterior orientation parameters 280 Eye base to height ratio 280 F FCODE 255 Feature collection 280 Feature collection mode 280 Feature editing mode 280 Feature extraction 280 Feature ID 280 Feature project 281 Features collecting and editing 171 Fiducial 281 center 281 marks 45 Fit Scene icon 6 Fixed Cursor Mode icon 7 Flight path 36 Floating mark 281 Focal length 44 281 Focal plane 44 G GCP 281 Geocentric 281 coordinate system 42 Stereo A
111. ch uses digital image correlation techniques to determine the image coordinate positions of a feature appearing on the left and right images of the stereopair During 3D feature collection the elevation of the 3D floating cursor must be continually adjusted so that the floating cursor rests on the surface of the feature being collected In order to interpret and collect 3D information directly from imagery at least two overlapping images taken from different perspectives are required When using aerial photography the photography is captured from two different camera exposure stations located along the direction of flight As a result a strip of overlapping images is captured The amount of overlap varies according to distance between the two camera exposure stations A greater distance between photographic exposure separations results in less overlap A smaller photographic exposure separation results in greater overlap Sixty percent overlap is the optimum overlap between the left and right photographs or images comprising a stereopair For an illustration of overlap see Figure 12 In order to collect 3D information from a stereopair the following input information is required e position of each image comprising a stereopair that is X Y and Z referenced to a ground coordinate system e the attitude or orientation of each image comprising a stereopair which is defined by three angles Omega Phi and Kappa and e camer
112. chnical University of Surveying and Mapping and Publishing House of Surveying and Mapping Beijing China Wolf P R 1980 Definitions of Terms and Symbols used in Photogrammetry Manual of Photogrammetry Ed Chester C Slama Falls Church Virginia American Society of Photogrammetry 1983 Elements of Photogrammetry New York McGraw Hill Inc Wong K W 1980 Basic Mathematics of Photogrammetry Manual of Photogrammetry Ed Chester C Slama Falls Church Virginia American Society of Photogrammetry Yang X 1997 Georeferencing CAMS Data Polynomial Rectification and Beyond Dissertation University of South Carolina Columbia SC Yang X and D Williams 1997 The Effect of DEM Data Uncertainty on the Quality of Orthoimage Generation Proceedings of GIS LIS 97 Cincinnati Ohio Works 273 Stereo Analyst Works 274 Glossary H Introduction Numerics H Symbols Stereo Analyst The following glossary defines terms commonly used in Stereo Analyst 2D Images or photos in X and Y coordinates only there is no vertical element Z to 2D images Viewed in mono 2D images are good for qualitative analysis 3D Images or photos in X Y and Z vertical coordinates Viewed in stereo 3D images approximate true Earth features 3D floating cursor The 3D floating cursor is apparent when you have a DSM that is two images of approximately the same area displayed in t
113. ction with an emitter Now you can add a second image to the Main View so that you can view the overlap portion of the two images in stereo From the File menu of the Digital Stereoscope Workspace select Open Add a Second Image for Stereo In the Select Layer To Open dialog navigate to the directory where you loaded the images and select the image la right img Click OK in the Select Layer To Open dialog If you receive the following message prompting you to save raster edits click No in the dialog Kitentian 2 Do you ih to quaeve Hon raster edir Click No Click OK to generate pyramid layers for this image too Aiea The fps la ihi imag does nol barre Pulls resaltos peed A owes fur mapep rath peered leper an Cus so ieradenng oeramance depending an the are of the rage dl pou Be te compute complete breed pli Lg rice e If you have not viewed an image before you are prompted to create pyramid layers Pyramid layers of the image la right img make it display faster in the Workspace at any resolution NOTE The following picture displays the images in Color Anaglyph Stereo That is so you can view the images in this book using red blue glasses Your images will appear different if you have your stereo mode set to Quad Buffered Stereo You notice that the initial image la left img no longer displays as a typical raster red green blue image This is due to the default settings of Stereo Analys
114. ctive status is indicated by its apparent depression in the Stereo Analyst feature toolbar The active tool can be locked for repeated use using the Lock tool Adjusted stereopair An adjusted stereopair is a pair of images displayed in a Digital Stereoscope Workspace that has a map projection system associated with it Aerial photographs Photographs taken from vertical or near vertical positions above the Earth captured by aircraft or satellite Photographs used for planimetric mapping projects Aerial triangulation AT The process of establishing a mathematical relationship between images the camera or sensor model and the ground The information derived is necessary for orthorectification DEM generation and stereopair creation Affine transformation Defines the relationship between the pixel coordinate system and the image space coordinate system using coefficients Air base The distance between the two image exposure stations See also Base height ratio Airborne GPS A technique used to provide initial approximations of exterior orientation which defines the position and orientation associated with each image as they existed during image capture See also Global positioning system Airborne INS INS stands for inertial navigation system Airborne INS data is available for each image and defines the position and orientation associated with an image as they existed during image capture American Standard Code for Informa
115. cuments which are delivered as PDF files suitable for printing or on line viewing and On Line Help Documentation delivered as HTML files The PDF documents are found in lt IMAGINE_HOME gt help hardcopy Many of these documents are available from the Leica Geosystems Start menu The on line help system is accessed by clicking on the Help button in a dialog or by selecting an item from a Help menu In Stereo Analyst the names of menus menu options buttons and other components of the interface are shown in bold type For example In the Select Layer To Add dialog select the Files of type dropdown list When asked to use the mouse you are directed to click double click Shift click middle click right click hold drag etc e Click designates clicking with the left mouse button Conventions Used in This Book xiv Stereo Analyst Double click designates rapidly clicking twice with the left mouse button Shift click designates holding the Shift key down on your keyboard and simultaneously clicking with the left mouse button Middle click designates clicking with the middle mouse button Right click designates clicking with the right mouse button Hold designates holding down the left or right as noted mouse button Drag designates dragging the mouse while holding down the left mouse button Stereo Analyst has additional mouse functionality Control left designates holding both the Contro
116. d Polyline 1 Length 173 6013 meters This means that the length of the entire segment of sidewalk you digitized is approximately 173 meters long 2 Notice the second line Stereo Analyst Take 3D Measurements 157 Z difference 9 0349 meters Z mean 248 6154 meters This means that the elevation change between the first point and the last point Z difference is approximately 9 meters The average elevation of the polyline Z mean is approximately 249 meters NOTE The 3D coordinates associated with the starting point of the polyline are displayed as Pt 1 3 Notice the statistics for Pt 2 in this example Pt 2 477761 466880 4761556 588114 meters 252 5246 meters Delta z 0 0007 meters Slope 0 0307 Azimuth 103 6312 degrees These statistics give the X and Y coordinates and Z in meters for the second vertex associated with the polyline The Delta z value is the difference in elevation between Pt 1 and Pt 2 Slope is computed as the difference in elevation between two points that is Delta Z divided by the distance between the same two points Azimuth is the direction of a line segment relative to North Refer to the following figure In this case the azimuth would be approximately 90 PE1 e 4 Scroll down to the end of the Pt measurements to reach the Angle measurements JD Manus Tool oB X dai E Aree MENG ATM TIA made 2401 ARP netur NS E EE d Pea deus Angle measurements are listed afte
117. d include the image coordinates of the GCPs and tie points along with the known ground coordinates of the GCPs A simplified version of the least squares condition can be broken down into a formula as follows V AX L including a weight matrix P where V the matrix containing the image coordinate residuals A the matrix containing the partial derivatives with respect to the unknown parameters including exterior orientation interior orientation X Y Z tie point and GCP coordinates X the matrix containing the corrections to the unknown parameters L the matrix containing the input observations that is image coordinates and GCP coordinates The components of the least squares condition are directly related to the functional model based on collinearity equations The A matrix is formed by differentiating the functional model which is based on collinearity equations with respect to the unknown parameters such as exterior orientation The L matrix is formed by subtracting the initial results obtained from the functional model with newly estimated results determined from a new iteration of processing The X matrix contains the corrections to the unknown exterior orientation parameters The X matrix is calculated in the following manner 1 X APA A PL where X the matrix containing the corrections to the unknown parameters Digital Mapping Solutions 57 Stereo Analyst A the matrix containing the partial deri
118. d stretch This is particularly evident along the diagonal that joins the two selected polygons 16 Fine tune the position of each vertex to eliminate any warping or stretching NOTE Sometimes the corner of a Feature of interest will be occluded in the Active Image as is the case of the bottom right vertex in this model You must estimate where that corner lies Stereo Analyst Texturizing the Model 225 Texturize a Perspective Distorted Face Stereo Analyst 17 18 19 Right click outside of the model to deselect the faces The front face of the model is textured Save the model by selecting File gt Save As gt Multigen OpenFlight Database from the Texel Mapper menu bar Enter texel_mapper_tour flt in the Save As dialog and click OK It is the nature of photography that the sides of features may be distorted due to perspective That is objects or vertices that are further away from the camera lens may appear smaller than those that are closer to the camera lens If we were to simply use the affine map mode to map a perspective distorted texture directly onto the model we would end up with a very warped and stretched texture rather than an accurate depiction of the model You can compensate for these perspective distortions while texturizing a model by adjusting the position of the model so that it mimics as closely as possible the position Field of View FOV and perspective of the feature in th
119. d were later extended to robust estimation Wang 1990 The most common robust estimation method is the iteration with selective weight functions Based on the scientific research results from the photogrammetric community LPS Project Manager offers two robust error detection methods within the triangulation process Itis worth mentioning that the effect of the automatic error detection depends not only on the mathematical model but also depends on the redundancy in the block Therefore more tie points in more overlap areas contribute better gross error detection In addition inaccurate GCPs can distribute their errors to correct tie points therefore the ground and image coordinates of GCPs should have better accuracy than tie points when comparing them within the same scale space Next you can learn about stereo viewing and feature collection This information prepares you to start viewing and digitizing in stereo Next 59 Stereo Analyst Next 60 Stereo Viewing and 3D Feature Collection Introduction This chapter describes the concepts associated with stereo viewing parallax the 3D floating cursor and the theory associated with collecting 3D information from DSMs o Principles of Stereo Viewing Stereoscopic Viewing On a daily basis we unconsciously perceive and measure depth using our eyes Persons using both eyes to view an object have binocular vision Persons using one eye to view an object have monocular vi
120. d y axis are parallel to the x axis and y axis in the image plane coordinate system The z axis is the optical axis therefore the z value of an image point in the image space coordinate system is usually equal to the focal length of the camera f Image space coordinates are used to describe positions inside the camera and usually use units in millimeters or microns This coordinate system is referenced as image space coordinates x y z in this chapter Figure 15 Image Space and Ground Space Coordinate System y Image coordinate system Za Height Ground coordinate system gt X Scanning Aerial Photography 41 Ground Coordinate System A ground coordinate system is usually defined as a 3D coordinate system that utilizes a known geographic map projection Ground coordinates X Y Z are usually expressed in feet or meters The Z value is elevation above mean sea level for a given vertical datum This coordinate system is referenced as ground coordinates X Y Z in this chapter Geocentric and Topocentric Coordinate System Terrestrial Photography Stereo Analyst Most photogrammetric applications account for the curvature of the Earth in their calculations This is done by adding a correction value or by computing geometry in a coordinate system that includes curvature Two such systems are geocentric and topocentric coordinates A geocentric coordinate system has its origin at the center of the Eart
121. data into other products for various applications For example if 3D point positions along a river bank have been collected the information can be used to create a DEM for that specific area of interest The DEMs generated for the successive time periods can be statistically compared to determine rates of erosion and deposition and the change in volume If photography for various time periods is available the same river bank area can be viewed and collected in 3D Click the Clear View icon amp to clear the Digital Stereoscope Workspace In the next tour guide you are going to use all of the techniques you have learned in the previous tour guides to collect features from a DSM Next 169 Stereo Analyst Next 170 Collecting and Editing 3D GIS Data Ej Introduction In the previous tour guides you have learned about the basic elements of Stereo Analyst You have learned how to open DSMs in the Digital Stereoscope Workspace and manipulate them so that they can be viewed in stereo You have also learned how to adjust parallax and cursor elevation You can now create your own block files using information from external sources Also you can check block files to ensure their accuracy using check points Finally you learned how to collect 3D information from a DSM You are going to use these techniques in order to collect features from a DSM This tour guide shows you how to use the tools provided by Stereo Analyst
122. degree Delta Z Difference in elevation between points DEM See Digital elevation model Terms 278 Stereo Analyst Digital elevation model Continuous raster layers in which data file values represent elevation DEMs are available from the USGS at 1 24 000 and 1 250 000 scale Digital orthophoto An aerial photo or satellite scene that has been transformed by the orthogonal projection yielding a map that is free of most significant geometric distortions Digital photogrammetric workstations DPW These include PCI OrthoEngine SOCET SET Intergraph Zeiss and others Digital photogrammetry Photogrammetry as applied to digital images that are stored and processed on a computer Digital images can be scanned from photographs or can be directly captured by digital cameras Digital stereo model DSM Stereo models that use imaging techniques of digital photogrammetry that can be viewed on desktop applications such as Stereo Analyst Digital terrain model DTM A DTM is a discrete expression of topography in a data array consisting of a group of planimetric coordinates X Y and the elevations Z of the ground points and breaklines See also Breakline Direction of flight Images in a strip are captured along the aircraft or direction of flight of the satellite Images overlap in the same manner as the direction of flight Disabled tool In Stereo Analyst a disabled tool is a tool that is not available to you based on t
123. dewalk Stereo Analyst Take 3D Measurements 154 2 Click and hold the wheel and zoom out of the image until the entire sidewalk can be seen in the Main View X parallax increases as you digitize in this direction Notice that as you travel southward along the sidewalk the x parallax increases Remember x parallax is a function of elevation Once you begin to digitize in those areas you have to adjust the 3D floating cursor so that it rests on the terrain while the measurements are being taken Now that you have examined the sidewalk you are about to digitize you can take a measurement In the next series of steps you are going to take a measurement using the Polyline tool ri For information about adjusting the height of the cursor to rest on a particular feature of interest see Cursor Height Adjustment on page 105 3 Click in the 3D Measure tool and select the Polyline tool The Polyline tool allows for the continuous 3D collection of line segments Each vertex associated with the start and end of a line segment as well as all those in between has a 3D coordinate associated with it The slope azimuth and difference in elevation between the start and end of a line segment are also recorded 4 Move your mouse into the Main View click and hold the wheel and zoom into the northern point of the sidewalk Notice that as you zoom into the origin of the sidewalk the cursor appears to separate This
124. displayed All operations performed using the toolbar icons can also be performed with the menu bar options Stereo Analyst is also equipped with a feature toolbar These tools allow you to create and edit features you collect from your DSMs Stereo Analyst has built in checks that determine whether you are creating or editing features therefore icons are only enabled when they are usable Table 3 shows the Stereo Analyst feature tools Table 3 Stereo Analyst Feature Toolbar Select Click the Select icon to select an existing feature in a feature project You can then use some of the feature editing tools to change it Box Click this icon to drag a box around existing 4 Feature features in a feature project You can then perform operations on multiple features at once Lock Unlo Click the unlocked icon to lock a feature ck collection or editing tool for repeated use When Gi a you are finished click the locked icon to unlock the tool Cut Click this icon to cut features or vertices from de features Copy Click this icon to copy a selected feature Paste Click this icon to paste a feature you have cut or El copied Orthogona Click this icon to create features that have only LI 90 degree angles The tool restricts the collection of features to only 90 degrees About Stereo Analyst 8 Next Stereo Analyst Table 3 Stereo Analyst Feature Toolbar Continued
125. djust the cursor elevation by rolling the mouse wheel until it rests on top of the roof of the building For more information on adjusting the elevation of the cursor see Position the 3D Cursor Alternately you can use the Terrain Following Cursor to ensure that the cursor is always on the feature of interest To enable the Terrain Following Cursor select Utility gt Terrain Following Cursor The Building 1 feature class is depressed indicating it is active and you may collect this type of feature from the DSM Jic sow bef DE i AS m y a aa dem Start at this corner sms a of the roof al dl fw Do TC a A o You can tell the cursor is positioned on the roof since it appears in the same position in the Left and Right Views 4 Click to collect that corner of the roof then move the mouse right and continue to digitize along the roof line adjusting the cursor elevation and x parallax as necessary Stereo Analyst Collect Building Features 185 As you approach the display extent of the Main View the image automatically pans so that you can continue digitizing The image area at the edge of the Main View that activates panning is called the auto panning trigger region The width of this region can be adjusted by changing the setting for Auto Panning Trigger Threshold jn the Stereo Analyst Digitizing Options Other adjustments for panning and roaming can also be made in the Stereo Anal
126. e nnn 114 Add a Second Image eee 116 Open the Create Stereo Model Dialog 117 Name the Block File leen 118 Enter Projection Information oooo 119 Enter Frame 1 Information c n 121 Apply the Information o ooo oooo ooo mos 125 Open the Block File lt lt lt lt 126 Next 3 ae eS aa a He ee qe RUE a a D cq DU TN 127 of a DSM xa usus oe ee aa oe ee L29 Introduction es 129 Getting Started 2 2 2 ee ee 130 Open a Block File nna 130 Open the Stereo Pair Chooser 132 Open the Position Tool 135 Use the Position Tool 136 First Check Point o o o o oooooo es 136 Second Check Point leen 139 Third Check Point llle 140 Fourth Check Point lle 141 Fifth Check Point err 142 Sixth Check Point eee 143 Seventh Check Point eee eee eee 144 Close the Position Tool 145 N t o RC PPP PII PCI 146 Measuring 3D Information ccr ee ee 147 Stereo Analyst Introduction ern onm nnn on 147 Getting Started ss 148 Open a Block File 148 Open the Stereo Pair Chooser 150 Take 3D Measurements cr n n n n 152 Open the 3D Measure Tool and the Position To
127. e NUMERIC width 5 numdecs 0 name iFIDi 1 type FLOAT width 12 numdecs 2 name iAreai ASCII File Example 259 Stereo Analyst 2 type 3 type Number of Shape 0 Attribu 0 14 1 80 2 12 3 26 Number Part Numbe 0 0 000000 1 0 000000 2 0 000000 3 0 000000 4 0 000000 5 0 000000 6 0 000000 7 0 000000 8 0 000000 9 0 000000 10 0 000000 11 0 000000 Shape Cla FCode 130 Shape Typ Number of 0 type 1 type 2 type Number of Shape 0 Attribu 0 1 1 49 2 24 Number Part Numbe 0 0 000000 1 0 000000 2 0 000000 3 0 000000 4 0 000000 5 FLOAT width FLOAT width Shapes 1 te Values 000000 8 480000 9 830000 3 790000 of Parts 1 0 r of Points 1 477696 910594 477702 250185 477714 423688 477716 098500 477728 114636 477724 339682 477735 601556 477732 200530 477724 137993 477721 404243 12 numdecs 12 numdecs 2 4761586 4761602 4761600 4761607 4761604 4761595 4761593 4761583 4761583 4761572 826069 537792 282062 085565 300293 227101 899420 888528 551767 958093 2 name 2 name 262 263 265 266 262 263 265 256 264 264 iPerimeteri iAvg Zi 175821 426152 504668 890308 354671 610381 574982 712508 496121 389131 477709 656544 4761572 711264 266 593709 477696 910594 4761586 826069 262 175821 ss 3 ipri hi g
128. e view In the following illustration the roof features display Click the 3D Feature View icon Bl to close the view Click outside the tower in the Main View to deselect it In the last two sections you practiced collecting 3D buildings using the 3D Polygon Extend tool In this portion of the tour guide you are going to use another handy tool the Orthogonal Snap tool With it you can easily create 90 angles Open the Position Tool Stereo Analyst Click the Position tool icon in the toolbar of the Digital Stereoscope Workspace The Digital Stereoscope Workspace adjusts to accommodate the Position tool In the Position tool type the value 477623 in the X field then press Enter on your keyboard Type 4761050 in the Y field then press Enter Type 245 39 in the Z field then press Enter Collect Building Features 195 5 Type 0 8 in the Zoom field then press Enter The following building displays in the Digital Stereoscope Workspace All of its corners are 90 angles You can use the Orthogonal Snap tool in the collection of this building o ML 1 Mi git _ a 6 Click the Close icon X in the Position tool to maximize the display area 7 Adjust the zoom so that the building fills the Main View 8 Adjust the x parallax as necessary Select the Building Feature and Digitize Stereo Analyst 1 From the Feature Class Palette at the left of the Digital Stere
129. e 2D image Select karolinerplatz right from the Active Image dropdown list You can see that this is an example of a perspective distorted image The far corner of the building seems smaller that the near corner Texturizing the Model 226 2 Check the Wireframe checkbox so you can see the image through the model Adjust the Active Image 1 To zoom in on the Active Image select the Image Options mode by clicking the Mm button on the Texel Mapper toolbar 2 Hold the middle mouse button and drag to zoom in Hold the Left mouse button and drag to pan through the image Display as much of the left side of the building as possible It is important that you are still able to see all of the vertices in the picture Select the Faces 1 Enter the Model Options mode by clicking the x button on the Texel Mapper toolbar 2 Drag the cursor so that the left side of the model is entirely visible in the workspace 3 Right hold and drag a selection box that intersects all of the polygons on the right side of the model All of these polygons are highlighted in the workspace Align the Model 1 Inthe Model Options dialog click the Geometry Locked icon T to unlock the geometry The vertices of the selected faces display as yellow boxes Stereo Analyst Texturizing the Model 227 Stereo Analyst 2 Drag each of these vertices so that they rest just outside of the corresponding building corners in the Active Image
130. e Options icon zs on the Texel Mapper toolbar The Tile Options dialog displays Create a new Image Class by clicking the Add Class icon next to the Image Class dropdown list The New Image Class dialog displays Enter Roof into the text box and click OK Roof appears in the Image Class dropdown list To add an image to the Building Sides class click the Add Image button next to the Image Name dropdown list A File Selector displays Select JFIF from the Files of Type dropdown list Tiling a Texture 235 Autotiling the Rooftop Stereo Analyst Select metal_roofing jpg from the list of files On the Options tab check No Stretch Click OK The image metal roofing is added to the Roof Image Class and displays in the Texel Mapper workspace The Texel Mapper provides the ability to automatically tile all of the rooftops or walls on all of the models that are displayed in the workspace Enter the Autotile Options mode by clicking the Autotile button El on the Texel Mapper toolbar The Autotile Options dialog displays Select Roof from the Geometry Type dropdown list Check the Apply To Locked Geometry checkbox All of the rooftop polygons on the model are highlighted 4 Enter 1 000 in the Scale field and click Apply The metal_roofing tile is uniformly applied to the roof of the model 5 Click the Clear Highlight button Tiling a Texture 236 Orient the Tiles Stereo Analyst
131. e Tool Palette at any time First create the custom feature class Parking Lot then you can use the Boundary Snap tool to join the parking lot with the forest feature From the Feature menu select Feature Project Properties Click the Feature Classes tab in the Feature Project dialog Click the Create Custom Feature Class button In the Create Custom Class dialog type Parking Lot in the Feature Class field Type parkinglot in the Filename field Click the Category dropdown list and choose Buildings and Related Features Click the Display Properties tab Click Polygon in the Select shape for drawing field Click OK in the Create Custom Class dialog Click No in the dialog asking you if you want to save the new class to the global features In the Feature Project dialog click the Category dropdown list and select Buildings and Related Features Click the checkbox next to Parking Lot then click OK in the Feature Project dialog The Parking Lot class displays on the Feature Tool Palette Collect a Forest Feature 213 Su ml BHEZUIHEHEMCEU es CUL os saa Lescortisaoge The new feature class is added to the bottom of the Feature Class Palette Use the Boundary Snap Tool This forest has a neighboring parking lot with which it shares a boundary You can use the Boundary Snap tool to connect them You can only share boundaries with features that are at the same elevation 1 Zoom to see the parking lot at the
132. e adjusts to accommodate the Position tool The Position tool occupies the lower portion of the Digital Stereoscope Workspace 2 Inthe Position tool type the value 477609 in the X field then press Enter on your keyboard 3 Type 4761280 in the Y field then press Enter 4 Type 263 78 in the Z field then press Enter Stereo Analyst Collect Building Features 183 Type 0 8 in the Zoom field then press Enter NOTE The zoom extent is an approximate value which is recorded to four decimal places The following building displays in the Digital Stereoscope Workspace Click the Close icon X in the Position tool to maximize the display area Zoom in so that the building fills the Main View Adjust the x parallax as necessary Select the Building Feature and Digitize Stereo Analyst Now that you have located the correct building you can select the Building 1 feature class and start digitizing using some of the feature collection tools in Stereo Analyst From the list of feature classes click to select the Building 1 icon E Bulkeg mi Once you select the feature class it appears to be depressed and outlined in the Feature Class Palette Notice that the Building 1 i class has a border around ame FF Light Dey Peel which indicates it is active Collect Building Features 184 2 Move your mouse into the display area and position the cursor at the northernmost corner of the building 3 A
133. e aerial photography or imagery Aerial photographs have the optical axis of the camera directed toward the Z axis of the ground coordinate system If ground based or terrestrial imagery is being used the Y axis should be selected as the photo direction When you have finished the Common tab of the Create Stereo Model dialog looks like the following Open the Create Stereo Model Dialog Creale Seres Model Projection information Frame Once the common displays here elements are specified you can enter information about the first image in the Frame 1 tab Dock erum g mem Prospecto LITIM Zem 11 Spheei GAE 1560 Dane MADES Maps Dra Catesan rii AwagaHeg Pem a Degrees mega Pri Fac Z ni E Fhota Dechert Enter Frame 1 Next you must define the parameters of the camera that collected Information the first image you intend to use in the block file To incorporate this information you must do so in the Frame 1 tab of the Create Stereo Model dialog 1 Click the Frame 1 tab located at the top of the Create Stereo Model dialog Crealo Steres Model Demon Framed Frome 2 Tie Posa This information is also kasga Heres interne Allie Tapes Camas Let la left md lenge la Fils dlrs J QUO H palcos EE DMG mentis in the Frame 2 tab Ar UND altos Notice that the Image filename section of the Frame 1 tab
134. e display here zu APDO A 40 GIL k of 13000 The views resize to accommodate the Feature Class Palette The classes you selected in the Feature Classes tab of the Feature Project dialog display here in the Feature Class Palette The Feature Class Palette Once you select feature classes you want to digitize in the DSM they appear in a column to the left of the Main View This area of the Digital Stereoscope Workspace is referred to as the Feature Class Palette Notice that to the immediate right of each feature class there is a icon which accesses feature properties By clicking this icon you can access attribute information for all features of that particular type Also notice a sj icon immediately below the feature properties icon of each feature class By clicking this icon an attribute table occupies the lower portion of the Digital Stereoscope Workspace Clicking it again causes the Attribute table to close Create a New Feature Project 182 Collect Building Features Collect the First Building This section shows you how to collect a building then make the feature 3D by using the 3D Polygon Extend tool Open the Position Tool If you remember from Checking the Accuracy of a DSM you can use the Position tool to drive to certain coordinate positions in an image 1 Click the Position tool icon in the toolbar of the Digital Stereoscope Workspace The Digital Stereoscope Workspac
135. e project file fpj contains all of the feature class and image information associated with a feature project A feature project file contains references to the following information e feature class files e LPS Project Manager block file or stereopair STP files and e specific references to the individual images contained within an LPS Project Manager block file or STP file Stereo Analyst Feature Project and Project When a feature project opens in Stereo Analyst all of the information contained within the feature project file is referenced for subsequent display and use in Stereo Analyst The following example illustrates a feature project containing 20 unique feature classes and two separate LPS Project Manager block files each block file containing one stereopair FeatureProjectDescription ii AssociatedFeatureClasses id idi idt id s id s id s id s id s id s id s id s id s id s id s id s id s id s id s id s id s S S S ProjectDate ProjectScale ProjectLocation SceneName Cereo cereo cereo Cereo Cereo cereo tereo Cereo tereo cereo cereo Cereo tereo cereo cereo Cereo Cereo cereo cereo Cereo analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes analyst wes a
136. e that you would like to digitize an additional portion of the road Using the Polyline Extend tool in Stereo Analyst you can add length to an existing feature 1 Make sure that the Selector tool is enabled in the Stereo Analyst feature toolbar 2 Zoom in to see the end of the road 3 Click to select the end of the road feature you just digitized The vertices at the end of the road are visible 4 Click the Polyline Extend tool amp 5 Click on the last vertex you digitized and continue collecting vertices along the road 6 Click to continue to digitize the road Note that the Parallel Line tool is still active so the road again has parallel lines 7 Continue to digitize the road until you come to the tower you digitized in Collect the Second Building ES The road feature has been extended to the tower you collected earlier in this Tour Guide 8 Double click to terminate the collection of the road 9 Click outside the road to deselect it Stereo Analyst Collect Roads and Related Features 204 10 Click the Zoom to Full Extent icon sz All of the features you have digitized are apparent in the Main View Collect a River Some features you collect are not linear Such is the case with the Feature river located in this DSM you can use stream digitizing to easily collect a feature with irregular contours Select a Different Stereo Model The features you are going to collect are located
137. e y parallax to a comfortable viewing perspective Adjust and Rotate the Display 96 E Position the 3D Cursor Stereo Analyst Click the Zoom to Full Extent icon ei f E 2j The full DSM displays in the Digital Stereoscope Workspace In Stereo Analyst the 3D position of the cursor is very important Because you may want to collect 3D features you must be able to position the cursor on the ground on a rooftop or some other feature You can adjust the elevation of the cursor in a number of ways For more information about how to position the cursor please refer to Cursor Height Adjustment on page 105 With the DSM fit in the window you use the OverView adjust the DSM so that you can see a portion of it that has changes in elevation Click on the Zoom to 1 1 icon an Click on an edge of the crosshair in the OverView Hold and drag it to the area of the expressway that runs through the approximate center of the image Adjust the display of the DSM in the views by moving the link box The expressway is constructed in a number of levels Position the 3D Cursor 97 Stereo Analyst Three levels are represented Lz in this portion of the expressway n which is a good location for adjusting cursor elevation Zoom in to see a detailed portion of the expressway with many overpasses Adjust the x parallax and y parallax as necessary Position the cursor over one of the elevated areas of the express
138. eO nn 18 Example 2 424 4 4 bah da babe ela eee e do do ds 18 Example 3 s 385 ayes acce a te eel wt Sy a a 18 Example 4 aaa y a a es 19 Stereo Analyst Table of Contents iii Example 5 ssc ee eee a a n E nin 19 Geographic Imaging ee eee 19 From Imagery toa 3D GIS 21 Imagery VY PES s xxix p Ri RET RC ERE 22 Workflow aa nnn 22 Defining the Sensor Model llle oo 23 Measuring GCPs icc m ah 23 Automated Tie Point Collection 24 Bundle Block Adjustment o o oooooooo oo 24 Automated DTM Extraction o ooo ooo 24 Orthorectification cler 25 3D Feature Collection and Attribution 25 3D GIS Data from Imagery 27 3D GIS Applications lens 27 Next uud ue uox Rake Rub RUSO MOREM ur ee ea 30 Photogrammetry use ue anu ew wor ase eee aa L Introduction een 31 Principles of Photogrammetry 31 What is Photogrammetry o o o o o ooo ooo 31 Types of Photographs and Images 34 Why use Photogrammetry ees 35 Image and Data Acquisition 35 Scanning Aerial Photography 37 Photogrammetric Scanners eres 37 Desktop Scanners ns 38 Scanning Resolutions ee es 38 Coordinate Systems es 40 Terrestrial Photography
139. eature part The following example illustrates 5 points that is vertices associated with a feature 0 477632 419597 4761198 995795 249 739925 0 000000 1 477674 118857 4761258 376408 248 880872 0 000000 2 477691 239580 4761246 461239 242 856737 0 000000 3 477648 942288 4761185 853104 242 626527 0 000000 4 477632 419597 4761198 995795 249 739925 0 000000 Each row of information contains Point ID X Y Z and O indicating the end of the line Part Number 2 repeat for each feature element or part comprising the specific feature Number of Points Repeat as above Part Number N repeat for each feature element or part comprising the specific feature Number of Points Repeat as above ASCII Categories 257 Shape Class 2 Shape Class N H ASCII File Example Stereo Analyst Shape Number 2 Shape Number 2 Description repeat for each shape collected for the given feature class Shape Number N Shape Number N Description repeat for each shape collected for the given feature class Shape Class 2 repeat for the second feature class defined and collected within Stereo Analyst Shape Class N repeat for each feature class defined and collected within Stereo Analyst The following example pertains to a Stereo Analyst Feature Project having the following characteristics e Eleven feature classes are defined within the Stereo Analyst feature project Only five feature classes have been used to collect f
140. eatures This includes shape class 1 building1 shape class 2 building2 shape class 3 pri highway shape class 7 unmonumented and shape class 10 woods e Shape Class 1 is a polygon feature class containing two 3D polygon shapes for example building1 Each building shape has five points that is vertices associated with it The 3D polygon shape has four attributes that is FID Area Perimeter AvgZ e Shape Class 2 is a polygon feature class containing one 3D polygon shape for example building2 The polygon shape has twelve points that is vertices associated with it The 3D polygon shape has four attributes that is FID Area Perimeter AvgZ e Shape Class 3 is a polyline feature class containing one 3D polyline shape for example primary highway The polyline shape has three attributes that is FID Length AvgZ and seven points that is vertices e Shape Class 7 is a point feature class for example unmonumented control containing seven 3D point shapes The point shape has two attributes that is FID AvgZ and each shape has one point that is vertex associated with it e Shape Class 10 is a polygon feature class that is woods containing one 3D polygon shape The 3D polygon shape has four attributes that is FID Area Perimeter AvgZ and the 3D polygon shape has nine points that is vertices associated with it ASCII File Example 258 Stereo Analyst The Stereo Analyst ASCII file b
141. ed to as symmetric lens distortion Terms 285 Stereo Analyst Raw stereopair A raw stereopair is a stereopair displayed in a stereo view that does not have a map projection system associated with it However because the images are of the same relative area they can be displayed in a stereo view Reference coordinate system Defines the geometric characteristics associated with events occurring in object space Also referred to as the object space coordinate system Rendering An image is rendered in the stereo view when it is redrawn at the scale indicated by the zoom in or out factor Rendering is another term for drawing the image in the stereo view Right hand rule A convention in 3D coordinate systems X Y Z that determines the location of the positive Z axis If you place your right hand fingers on the positive X axis and curl your fingers toward the positive Y axis the direction your thumb is pointing is the positive Z axis direction RMSE See Root Mean Square Error Root Mean Square Error RMSE Used to measure how well a specific calculated solution fits the original data For each observation of a phenomena a variation can be computed between the actual observation and a calculated value The method of obtaining a calculated value is application specific Each variation is then squared The sum of these squared values is divided by the number of observations and then the square root is taken This is the RMSE val
142. eel For information on cursor height adjustment see Position the 3D Cursor Use the Position Tool 138 Second Check Point Stereo Analyst As the 3D floating cursor is being adjusted the elevation value associated with the Z coordinate is adjusted in the status area Once the floating cursor is adjusted record the new Z coordinate value displayed in the Position tool To determine the offset associated with the original and displayed Z coordinate value subtract the old value from the new value The resulting value indicates the accuracy of the DSM over that specific check point Determining Stereo Model Accuracy Z Coordinate Like the X and Y coordinates you determine the accuracy of the Z elevation coordinate by subtracting your results from the values provided to you Original Check New Check Point A Point 1 Z Elevation 1 Z Elevation 247 24 247 2485 0 0085 Check that Enable Update button is not active and the Zoom is set to approximately 1 0 In the Position tool type the following X Y and Z values respectively 478067 22 4761584 73 and 259 96 Use the Position Tool 139 3 Position the cursor and visually interpret the location of the 3D floating cursor over the feature Compute X Y Coordinate and Z Elevation Accuracy Third Check Point Stereo Analyst For more detailed instructions see First Check Point If necessary adjust the image so tha
143. eft and or right until the same features overlap X Hold down the E left button gt MP a n RE Move the mouse in this direction Experiment with the x parallax by over adjusting to see the features separate again Return the images to their aligned positions Adjust and Rotate the Display 95 Adjust Y parallax Stereo Analyst Once the x parallax has been properly adjusted you can comfortably perceive the stereopair in 3D Now that you have learned how to adjust the x parallax of an image you can use some other methods to improve the display of the stereopair in the Main View At the same location you adjusted x parallax you can also experiment with adjusting y parallax Typically y parallax does not need as much adjustment as x parallax For more information please refer to Adjusting Y Parallax on page 104 Hold down the Y key on your keyboard while simultaneously holding down the left mouse button Move the mouse up and down until the same features overlap Hold down the left button gt gt Move the mouse in this direction Once you have moved the images sufficiently far apart you can perceive the y parallax as depicted in the following illustration which has been exaggerated for the purposes of this tour guide Y parallax is especially Y parallax apparent in this portion has been adjusted of the image note that the features do not overlap 3 Return th
144. egins here Stereo Analyst 3D ascii shapes file Version x x This file is in Stereo Analyst 3D ascii format and should not be altered The format of this file could change in future versions of Stereo Analyst Number of Classes 11 Shape Class 1 ibuildingli FCode 12000 Shape Type 3D POLYGON Number of Attributes 4 0 type NUMERIC width 5 numdecs 0 name iFIDi 1 type FLOAT width 12 numdecs 2 name iAreai 2 type FLOAT width 12 numdecs 2 name iPerimeteri 3 type FLOAT width 12 numdecs 2 name iAvg Zi Number of Shapes 2 Shape 0 Attribute Values 0 1 000000 1 1535 400000 2 188 440000 3 246 030000 Number of Parts 1 Part 0 Number of Points 5 0 477632 419597 4761198 995795 249 739925 0 000000 1 477674 118857 4761258 376408 248 880872 0 000000 2 477691 239580 4761246 461239 242 856737 0 000000 3 477648 942288 4761185 853104 242 626527 0 000000 4 477632 419597 4761198 995795 249 739925 0 000000 Shape 1 Attribute Values 0 2 000000 1 3001 500000 2 220 570000 3 256 220000 Number of Parts 1 Part 0 Number of Points 5 0 477715 040049 4761423 312186 254 413795 0 000000 1 477773 206585 4761413 022898 259 199663 0 000000 2 477782 550252 4761460 154519 258 961248 0 000000 3 477721 068481 4761473 489381 252 301078 0 000000 4 477715 040049 4761423 312186 254 413795 0 000000 Shape Class 2 ibuilding2i FCode 12001 Shape Type 3D POLYGON Number of Attributes 4 0 typ
145. eld adjusting x parallax and cursor elevation as necessary Once you have finished digitizing the field double click to close the polygon Zoom out by holding the wheel and moving the mouse toward you to see the entire polygon Your digitized field should look similar to the following The polygon border representing the open field displays after digitizing Evaluate Results Take the Fifth Measurements Stereo Analyst The measurements are reported in the text field of the 3D Measure tool NOTE Your measurements may differ from those presented here Use the scroll bar to see the first line of data associated with the polyline you just digitized Polygon 2 Polygon 2 Area 9 0418 acres Length 844 9017 meters Notice the second line of data Z difference 4 2958 meters Z mean 256 9078 meters Continue to scroll down to view the rest of the results in the 3D Measure tool text field You get results for each of the points you digitized to create the field boundary Another tool you can use to measure 3D information is the Point tool With it you can measure individual points in a DSM This technique is especially useful if you are attempting to collect 3D point positions to be used for creating a DEM In this section of the tour guide you are going to collect some points along the roof line of a building to see how its elevation changes Take 3D Measurements 165 3D Measurement Uses Measuring 3D point pos
146. eo Analyst tools to check the accuracy of the data In this portion of the tour guide you are going to work with the Position tool You can use the Position tool to check the accuracy of the DSM and the associated quality of the sensor model information contained in the block file With the stereopair 252 img and 253 img displayed in the Digital Stereoscope Workspace click the Position tool Once selected the Position tool becomes embedded in the bottom portion of the Digital Stereoscope Workspace Thus all of the tools required for checking accuracy are contained within one environment Open the Position Tool 135 Tools you open display at the bottom of the Workspace The views resize automatically to accommodate the tools E Use the Position Tool First Check Point Stereo Analyst To use the Position tool you are going to type in X Y and Z coordinates of check points Check points can be used to check the accuracy of the DSM in the block file Ensure that the Enable Update button is not checked in the Position tool Ensure that the Map X Y option is set to Map NOTE The units of the X Y and Z check point positions are determined based on the sensor model information contained in the block file Type 1 0 in the Zoom field NOTE The zoom is approximately 1 0 Use the Position Tool 136 In the Position tool double click the value in the X field and type the value 478221 57 then press Enter on
147. er de Gruyter Verlag Berlin Kraus K 1984 Photogrammetrie Band II D mmlers Verlag Bonn Krzystek P 1998 On the use of matching techniques for automatic aerial triangulation Proceedings of ISPRS commission III conference 1998 Columbus Ohio USA Kubik K 1982 An error theory for the Danish method ISPRS Commission III conference Helsinki Finland Li D 1983 Ein Verfahren zur Aufdeckung grober Fehler mit Hilfe der a posteriori Varianzsch tzung Bildmessung und Luftbildwesen Vol 5 1985 Theorie und Untersuchung der Trennbarkeit von groben PaBpunktfehlern und systematischen Bildfehlern bei der photogrammetrischen punktbestimmung Ph D dissertation Deutsche Geodatische Kommission Reihe C No Stereo Analyst Works 271 Stereo Analyst 324 L Y 1988 Interest operator and fast implementation IASPRS Vol 27 B2 Kyoto 1988 Mayr W 1995 Aspects of automatic aerotriangulation Proceedings of 45th Photogrammetric Week Wichmann Verlag Karlsruhe pp 225 234 Merriam Webster OnLine Dictionary ellipsoid at http www m w com 29 May 2000 Merriam Webster On Line Dictionary theodolites at http www m w com 29 May 2000 Moffit F H and E M Mikhail 1980 Photogrammetry New York Harper amp Row Publishers OpenGL Architecture Review Board 1992 OpenGL Reference Manual The Official Reference Document for OpenGL Release 1 Reading Addison Wesley Pub
148. er for the image and ground vectors to be within the same coordinate system the ground vector must be multiplied by the rotation matrix M The following equation can be formulated a kMA where Xa X x o Yp E m kM p No f Zp La The previous equation defines the relationship between the perspective center of the camera sensor exposure station and ground point P appearing on an image with an image point location of p This equation forms the basis of the collinearity condition that is used in most photogrammetric operations The collinearity condition specifies that the exposure station of the image ground point and its corresponding image point location must all lay along a straight line thereby being collinear Two equations comprise the collinearity condition f __ ee Ue E 1a Exterior Orientation 50 H Digital Mapping Solutions Space Resection Stereo Analyst One set of equations can be formulated for each ground point appearing on an image The collinearity condition is commonly used to define the relationship between the camera sensor the image and the ground Digital photogrammetry is used for many applications ranging from orthorectification automated elevation extraction stereopair creation stereo feature collection highly accurate 3D point determination and GCP extension For any of the aforementioned tasks to be undertaken a relationship between the camera sensor the ima
149. er or better with tablet v_control_3 V Control 3rd 4 bmp 1003 Point Third order or better recoverable r_v_control_3 Rec V Cont 3rd 5 bmp 1004 Point mark Spot elevation spot_elev Spot Elevation 6 bmp 1005 Point Boundary Monument With tablet b_mon_w_tab Bound Mon Tab 7 bmp 1006 Point Without tablet b_monument Bound Mon 8 bmp 1007 Point U S mineral or location monument us_min_mon U S Mineral 10 bmp 1008 Point Mon Topographic Contours Intermediate inter_cont Inter Contour 11 bmp 2000 Polyline Index ind_cont Index Contour 12 bmp 2001 Polyline Supplementary sup_cont Suppl Contour 13 bmp 2002 Polyline Depression depression Depression 14 bmp 2003 Polygon Cut Fill cut Cut Fill 15 bmp 2004 Polygon Boundaries National nat boundary National 17 bmp 3000 Polyline Boundary State or territorial state bound State Boundary 18 bmp 3001 Polyline County or equivalent county bound County 19 bmp 3002 Polyline Boundary Civil township or equivalent town boundary Town Boundary 20 bmp 3003 Polyline Incorporated city or equivalent city bound City Boundary 20 bmp 3004 Polyline Park reservation or monument park boundary Park Boundary 21 bmp 3005 Polyline Small park sm park bound lp a 22 bmp 3006 Polyline Bound U S Public Land Survey System Stereo Analyst Default Stereo Analyst Feature Classes 249 Table 9 Stereo Analyst Default Feature Classes Continued
150. ereo the brain automatically compares the relative positions of the building and the ground from the two different perspectives that is two overlapping images The brain also determines which is closer and which is farther the building or the ground Thus as left and right eyes view the overlap area of two images depth between the top and bottom of a building is perceived automatically by the brain and any changes in depth are due to changes in elevation During the stereo viewing process the left eye concentrates on the object in the left image and the right eye concentrates on the object in the right image As a result a single 3D image is formed within the brain The brain discerns height and variations in height by visually comparing the depths of various features While the eyes move across the overlap area of the two photographs a continuous 3D model of the Earth is formulated within the brain since the eyes continuously perceive the change in depth as a function of change in elevation The 3D image formed by the brain is also referred to as a stereo model Once the stereo model is formed you notice relief or vertical exaggeration in the 3D model A digital version of a stereo model a DSM can be created when sensor model information is associated with the left and right images comprising a stereopair In Stereo Analyst a DSM is formed using a stereopair and accurate sensor model information Using the stereo viewing and 3D
151. ereopair The independent left and right image cursors define the exact image positions of a feature on the images defining a stereopair It is referred to as a 3D floating cursor since the cursor commonly floats above below or on a feature while viewing in stereo The 3D floating cursor is the primary measuring mark used in Stereo Analyst to collect and measure accurate 3D geographic information 3D Floating Cursor and Feature Collection 69 E 3D Information from Stereo Models Stereo Analyst To collect 3D GIS data in Stereo Analyst the location of the cursor on the left image must correspond to the location of the cursor on the right image Using Stereo Analyst the two cursors that comprise the 3D floating cursor are adjusted simultaneously so that they fuse into one floating cursor that is located in 3D space on the feature being collected or measured The elevation of the 3D floating cursor can be adjusted as a function of x parallax Since the x parallax contained within a 3D DSM varies as a function of elevation the x parallax of the cursor must be adjusted so that the elevation of the cursor is equivalent to the elevation of the feature being collected When these two variables are equivalent the 3D floating cursor should rest on the surface of the feature being collected Stereo Analyst uses an approach referred to as automated terrain following to automatically adjust the x parallax of the 3D floating cursor This approa
152. error detection PE amp RS 1984 6 FGDC 1997 Content Standards for Digital Orthoimagery Federal Geographic Data Committee Washington DC F rstner W and E G lch 1987 A fast operator for detection and precise location of distinct points corners and centers of circular features Proceedings of Intercommission Conf on Fast Processing of Photogrammetric Data 2 4 June Interlaken Switzerland pp 281 305 Available from Institute of Geodesy and Photogrammetry ETH Zurich Free On Line Dictionary of Computing American Standard Code for Information Interchange from FOLDOC American Works 269 Stereo Analyst Standard Code for Information Interchange at http foldoc doc ic ac uk foldoc 24 October 1999 Free On Line Dictionary of Computing Charge Coupled Device from FOLDOC Charge Coupled Device at http foldoc doc ic ac uk foldoc 29 May 2000 Free On Line Dictionary of Computing GPS from FOLDOC GPS at http foldoc doc ic ac uk foldoc 29 May 2000 Gr n A 1978 Experiences with self calibrating bundle adjustment Proceedings of ACSM ASP Convention Washington Gr n A and E P Baltsavias 1988 Geometrically constrained multiphoto matching Photogrammetric Engineering and Remote Sensing Vol 54 5 pp 309 312 Heipke C 1996 Automation of interior relative and absolute orientation International Archives of Photogrammetry and Remote Sensing Vol 31 Part B3 pp 297 311
153. esection techniques can be used to determine the six exterior orientation parameters associated with an image Space resection assumes that camera information is available Space resection is commonly used to perform single frame orthorectification where one image is processed at a time If multiple images are being used space resection techniques require that a minimum of three GCPs be located on each image being processed Digital Mapping Solutions 51 Space Forward Intersection Stereo Analyst Using the collinearity condition the positions of the exterior orientation parameters are computed Light rays originating from at least three GCPs intersect through the image plane through the image positions of the GCPs and resect at the perspective center of the camera or sensor Using least squares adjustment techniques the most probable positions of exterior orientation can be computed Space resection techniques can be applied to one image or multiple images Space forward intersection is a technique that is commonly used to determine the ground coordinates X Y and Z of points that appear in the overlapping areas of two or more images based on known interior orientation and known exterior orientation parameters The collinearity condition is enforced stating that the corresponding light rays from the two exposure stations pass through the corresponding image points on the two images and intersect at the same ground point Figure 22 il
154. ew in overlap area 3D floating cursar D f i The cursor rests E on the same feature n j in both images Sp coordinate Mono view of left information and right images If the 3D floating cursor does not rest on the feature of interest the resulting image positions of the feature on the left and right image are incorrect Since the image position information is used in conjunction with the sensor model information to calculate 3D coordinate information it is important that the image positions of the feature be geographically accurate Next Now that you have learned about 3D imaging photogrammetry and stereo viewing you are ready to start the tour guides They are contained in the next section Stereo Analyst Next 72 Tour Guides Stereo Analyst 73 Stereo Analyst 74 Creating a Nonoriented DSM Introduction Using two overlapping aerial photographs or images a 3D stereo view can be created This is achieved by superimposing the overlapping portion ofthe two photographs The process of manually orienting two overlapping photographs has been extensively used with airphoto interpretation applications involving a stereoscope The two overlapping photographs are rotated scaled and translated until a clear and optimum 3D stereo view has been achieved This process is referred to as removing parallax Stereo Analyst extends the use of overlapping photography for the interpretation visualization and col
155. formed coordinates of the output pixel Nonoriented stereopair A nonoriented stereopair is made up of two overlapping photographs or images that have not been photogrammetrically processed Neither the interior nor the exterior orientation which define the internal geometry of the camera of the sensor as well as its position during image capture has been defined You can collect measurements from a nonoriented stereopair however the measurements are in pixels and 2D Nonorthogonality The degree of variation between the x axis and the y axis Object space coordinate system The origin is defined by the projection spheroid and datum of the area being imaged Terms 283 Stereo Analyst Oblique photographs Photographs captured by an aircraft or satellite deliberately offset at an angle Oblique photographs are usually used for reconnaissance and corridor mapping applications Off nadir Any point that is not directly beneath the detectors of a scanner but off to an angle The SPOT scanner allows off nadir viewing Omega o A measurement used to define camera or sensor rotation in exterior orientation Omega is rotation about the photographic x axis OpenGL OpenGL is a development environment that allows stereopairs to be displayed in a stereo view in 3D space For more information visit the web site www opengl org Orientation matrix A three by three matrix defining the relationship between two coordinate systems that
156. from picture element the smallest part of a picture image Point A point is a feature collected in Stereo Analyst that has X Y and Z coordinates A point can represent a feature such as a manhole cover fire hydrant or telephone pole You can collect multiple points for the purposes of creating a TIN or DEM Polygon A polygon is a set of closed line segments defining an area and is composed of multiple vertices In Stereo Analyst polygons can be used to represent many features from a building to a field to a parking lot Additionally polygons can have an added elevation value Polyline A polyline is an open vector attribute made up of two or more vertices In a DSM polylines have X Y and Z coordinates associated with them Principal point Xp Yp The point in the image plane onto which the perspective center is projected located directly beneath the interior orientation The origin of the coordinate system Where the optical axis intersects the image plane Pushbroom A scanner in which all scanning parts are fixed and scanning is accomplished by the forward motion of the scanner such as the SPOT scanner Pyramid layer A pyramid layer is an image layer that is successively reduced by a power of 2 and resampled Pyramid layers enable large images to be displayed faster in the stereo views at any resolution Radial lens distortion Imaged points are distorted along radial lines from the principal point Also referr
157. ft img a b a0 116 5926 bO 116 5700 al 0 000043 b1 0 023995 a2 0 023991 b2 0 000041 2 Click the Exterior tab Do not enter commas in the Exterior orientation CellArray 3 Using the following table type the six exterior orientation parameters into the Exterior tab Table 6 Exterior Orientation Parameters for Frame 1 la left img position rotation X 382496 9993 Omega 0 3669 Y 3765072 1510 Phi 0 1824 Z 3921 7234 Kappa 91 5355 Stereo Analyst Open the Create Stereo Model Dialog 123 When you have finished the Frame 1 tab of the Create Stereo Model dialog looks like the following EE E BR Next you enter information for the second image in the Frame 2 tab Corn Frame d intone Afing Type Cafres orta Focal Length Pinepla Ponit ms Pinepla Ponit e prr Exieriex Add Interior and Exterior Information for Frame 2 la right img Do not enter commas in the Interior and Exterior orientation CellArrays 1 Click the Frame 2 tab at the top of the Create Stereo Model dialog Information from the Frame 1 tab Focal Length and Principal Point xo and yo transfers to the Frame 2 tab automatically 2 Using the following table type the six coefficients into the Interior tab Table 7 Interior Orientation Parameters for Frame 2 la right img a b a0 116 2486 bO 116 8011 al 0 000018 bi 0 023992 a2 0 023987 b2 0 000017 3 Click the Exterior t
158. g 124 Table 8 Exterior Orientation Parameters for Frame 2 la right img 125 Table 9 Stereo Analyst Default Feature Classes a 249 Stereo Analyst xi Stereo Analyst xii Preface E About This Manual a Example Data E Tour Guide Examples Creating a Nonoriented DSM Creating a DSM from External Sources Stereo Analyst The Stereo Analyst User s Guide provides introductions to Geographic Information Systems GIS three dimensional 3D geographic imaging and photogrammetry tutorials and examples of applications in other software packages Supplemental information is also included for further study Together the chapters of this book give you a complete understanding of how you can best use Stereo Analyst in your projects Data sets are provided with the Stereo Analyst software so that your results match those in the tour guides Example data is optionally loaded during the software installation process into the lt IMAGINE_HOME gt examples Western directory IMAGINE HOME is the variable name of the directory where Stereo Analyst and ERDAS IMAGINE reside When accessing data files you replace IMAGINE HOME with the name of the directory where Stereo Analyst and ERDAS IMAGINE are loaded on your system A second data set is provided on the data CD that comes with Stereo Analyst This data set IMAGINE HOME VexamplesMa is used in some of the
159. g icon 9 Strip of photographs 287 Symmetric lens distortion 47 T Tangential lens distortion 46 287 Terrestrial photographs 34 42 287 Texels 287 Texture map 287 Theodolites 287 Tie point 288 TIN 288 Topocentric 288 coordinate system 42 coordinates 42 Topographic information 32 Transparency 288 Triangulated Irregular Network TIN Project 288 Triangulation 288 U Unit X and Y 265 Unit Z 265 United States Geological Survey 288 Unlock icon 8 Update Scene icon 7 USGS 288 Index 294 Vv V residual matrix 58 Vertex 288 Vertical exaggeration 288 Vertices 288 W Workspace 289 X X matrix 57 Xp Yp 285 X parallax 289 Y Y parallax 289 Z Zoom one to one icon 6 Stereo Analyst Index 295 Stereo Analyst Index 296
160. ge s in a project and the ground must be defined The following variables are used to define the relationship e exterior orientation parameters e interior orientation parameters and e Camera or sensor model information Well known obstacles in photogrammetry include defining the interior and exterior orientation parameters for each image in a project using a minimum number of GCPs Due to the costs and labor intensive procedures associated with collecting ground control most photogrammetric applications do not have an abundant number of GCPs Additionally the exterior orientation parameters associated with an image are normally unknown Depending on the input data provided photogrammetric techniques such as space resection space forward intersection and bundle block adjustment are used to define the variables required to perform orthorectification automated DEM extraction stereopair creation highly accurate point determination and control point extension Space resection is a technique that is commonly used to determine the exterior orientation parameters associated with one image or many images based on known GCPs Space resection uses the collinearity condition Space resection using the collinearity condition specifies that for any image the exposure station the ground point and its corresponding image point must lay along a straight line If a minimum number of three GCPs are known in the X Y and Z direction space r
161. ghlighted in the Digital Stereoscope Workspace Next collect a forest feature You can collect the forest that borders the river Position the DSM in the Digital Stereoscope Workspace at the origin of the river feature Collect a Forest Feature 208 E eek 2 Click the Woods feature i in the Feature Class Palette 3 From the feature toolbar select the Stream Digitizing tool gl 4 Click to collect the first vertex 5 Holdthe left mouse button and drag the 3D floating cursor adjusting the elevation as necessary over the forest boundary to trace the feature During the continuous collection of the polyline or polygon feature vertices are automatically placed over the traced X and Y locations 6 Double click to close the forest feature 7 Zoom out to see the entire feature in the Main View d aliti UE RN 48 AAA A cuc MU raa Leto 2nrs igg B biet The forest feature displays as a green filled polygon Reshape the Feature You can zoom in and reshape the feature to correct any mistakes you may have made in the stream digitizing process Stereo Analyst Collect a Forest Feature 209 1 Adjust the display of the image in the view to see details of the forest boundary 2 Click to select the forest feature 3 Click the Reshape icon 4 Zoom in to see a more detailed portion of the forest You can use Reshape to correct a portion of the border of the forest 5 Click hold
162. ght of each image as required Scaling the stereo model accounts for the differences in altitude as they existed when the left and right photographs were captured Translating the stereo model involves adjusting the relative X and Y positions of the left and right images in order to minimize x parallax and y parallax Translating the positions of the left and right images accounts for misaligned images along a flight line Rotating the left and right images adjusts for the large relative variation in orientation that is Omega Phi Kappa for the left and right images When viewing a pair of tilted overlapping photographs in stereo the left and right images must be continually scaled translated and rotated in order to maintain a clear continuous stereo model Thus it is your responsibility to adjust y parallax in order to create a clear stereo view Once properly oriented you should notice that the images are oriented parallel to the direction of flight which was originally used to capture the photography Scaling Translation and Rotation 67 Stereo Analyst When using DSMs created from sensor model information Stereo Analyst automatically rotates scales and translates the imagery to continually provide an optimum stereo view throughout the stereo model Thus the y parallax is automatically accounted for The process of automatically creating a clear stereo view is referred to as epipolar resampling on the fly As you roam thr
163. ght Views as a guide adjust the height of the cursor with the mouse wheel until the cursor rests on the ground Ensure that the cursor is at the same location in both images Click on a line segment of the polygon you created Click to select the 3D Polygon Extend tool from the feature toolbar Click to select any one of the vertices that makes up the roof line Click outside of the building to deselect it Stereo Analyst creates a 3D footprint of the building that touches the ground Collect Building Features 197 9 Zoom in or out until you can comfortably see the 3D polygon in the Main View A ei ae emus P cn a FO Emu E amp 4I OAL Toe ee Lr S 11000 The 3D building displays in the Digital Stereoscope Workspace Because it is a relatively short building the 3D effect is not as evident as with a tall building such as the tower 10 Click the Zoom to Full Extent icon a Collect Roads and Stereo Analyst also provides you with tools with which to collect Related Features roads and the like In this portion of the tour guide you are going to practice collecting a sidewalk first then you progress to roads Collect a Sidewalk You can locate the sidewalk to be digitized using the Position tool Open the Position Tool 1 Click the Position tool icon in the toolbar of the Digital Stereoscope Workspace The Digital Stereoscope Workspace adjusts to accommodate the Position tool 2 Inthe Position
164. gure 16 for an illustration of the three axes Over the last several years it has been common practice to collect airborne GPS and inertial navigation system INS information at the time of image collection If this information is available the external sensor model information can be directly input for use in subsequent photogrammetric processing If external sensor model information is not available most photogrammetric systems can determine the exact position and orientation of each image in a project using the bundle block adjustment approach Unlike traditional georectification techniques GCPs in digital photogrammetry have three coordinates X Y and Z The image locations of 3D GCPs are measured across multiple images GCPs can be collected from existing vector files orthorectified images DTMs and scanned topographic and cartographic maps GCPs serve a vital role in photogrammetry since they are crucial to establishing an accurate geometric relationship between the images in a project the sensor model and the ground This relationship is established using the bundle block adjustment approach Once established 3D GIS data can be accurately collected from imagery The number of GCPs varies from project to project For example if a strip of five photographs is being processed a minimum of three GCPs can be used Optimally five or six GCPs are distributed throughout the overlap areas of the five photographs Workflow 23 Aut
165. h ellipsoid The Z axis equals the rotational axis of the Earth and the X axis passes through the Greenwich meridian The Y axis is perpendicular to both the Z axis and X axis so as to create a three dimensional coordinate system that follows the right hand rule A topocentric coordinate system has its origin at the center of the image projected on the Earth ellipsoid The three perpendicular coordinate axes are defined on a tangential plane at this center point The plane is called the reference plane or the local datum The x axis is oriented eastward the y axis northward and the z axis is vertical to the reference plane up For simplicity of presentation the remainder of this chapter does not explicitly reference geocentric or topocentric coordinates Basic photogrammetric principles can be presented without adding this additional level of complexity Photogrammetric applications associated with terrestrial or ground based images utilize slightly different image and ground space coordinate systems Figure 16 illustrates the two coordinate systems associated with image space and ground space Scanning Aerial Photography 42 Figure 16 Terrestrial Photography Ground point A o UT YA The image and ground space coordinate systems are right handed coordinate systems Most terrestrial applications use a ground space coordinate system that was defined using a localized Cartesian coordinate system The image space coordin
166. he Digital Stereoscope Workspace The position of the 3D floating cursor position is determined by the amount of x parallax evident in the DSM and your positioning of it on the ground or feature or interest You adjust the position of the 3D floating cursor using your keyboard and your mouse See also x parallax 3D shapefile A 3D shapefile is a standard shapefile with the added Z or elevation dimension In Stereo Analyst you can create 3D shapefiles using feature collection tools such as Extend Feature which extends the corners of a feature for example a building to touch the ground blk The blk extension stands for a block file containing one or more images that can be viewed in stereo You can use the Stereo Pair Chooser to select a stereopair from a block file fp The fpj extension stands for feature project In an fpj project you can collect features in vector format from stereo imagery stp The stp extension stands for stereopair An stp image is made of two images x Kappa An angle used to define angular orientation x is rotation about the z axis Omega An angle used to define angular orientation is rotation about the x axis 9 Phi An angle used to define angular orientation is rotation about the y axis Symbols 275 Terms Stereo Analyst Active tool In Stereo Analyst the active tool is the one you are currently using to collect or edit features in a Feature Project Its a
167. he STP file supports IMG and TIF image files If the output STP file and the image files are not stored in the same directory the image name and path must be defined Output Image Number Second The output image number second field defines the image ID to be used for the right image comprising the stereopair of interest Inner Parameter Second The inner parameter second field defines the six affine coefficients computed from the epipolar resampling process associated with the interior orientation of the right image The units of the coefficients should be equivalent to the units used for the focal length The affine transform coefficients should be defined according to the image that is pixel to film format Outer Parameter Second The outer parameter second field defines the six exterior orientation values for the right image computed from the epipolar resampling process The units of the positional elements of exterior orientation must be equivalent to the UNIT X Y and UNIT Z definitions The following example illustrates the STP file used for a data set STP File Example 266 EPIPOLAR_OUTPUT_FILE GEOMETRY FRAME PROJECTION NAME UTM UNIT X Y METER UNIT Z2 METER RESAMPLING MODE 2 ROTATION ANGLE MODE 2 AVERAGE FLYING HEIGHT 7500 000000 EPIPOLAR FOCAL LENGTH 152 782 OUTPUT IMAGE FILE FIRST c2rgb50ep img OUTPUT IMA
168. he operation you are attempting to perform For example if you are using the Parallel Line tool to collect a road feature the Reshape tool is disabled as it has no application at the time you are collecting the feature however once you finish collecting the road feature the Reshape tool becomes enabled See also Enabled tool DLL See Dynamically loaded libraries DPW See Digital photogrammetric workstations DSM See Digital stereo model DTM See Digital terrain model Dynamically loaded library DLL A Dynamically Loaded Library is loaded by the Stereo Analyst application as they are needed DLLs provide added functionality such as stereo display and import export capabilities Earth Observation Satellite Company EOSAT A private company that directs the Landsat satellites and distributes Landsat imagery Elements of exterior orientation Variables that define the position and orientation of a sensor as it obtained an image It is the position of the perspective center with respect to the ground space coordinate system Ellipsoid A surface all plane sections of which are ellipses or circles Merriam Webster OnLine Dictionary 2000a Terms 279 Stereo Analyst Enabled tool An enabled tool is one that is active for your current application For example feature collection tools such as the Parallel Line tool are enabled when you are collecting features If your current application is feature editing then tools such
169. hly accurate geographic information such as orthorectified imagery Digital Terrain Models DTMs and 3D vector data sets e Remote sensing techniques such as multi spectral classification have traditionally been used for extracting geographic information about the surface of the Earth These approaches have been widely accepted within the GIS industry as the primary techniques used to prepare collect and maintain the data contained within a GIS however GIS professionals throughout the world are beginning to face the following issues Introduction 11 e The original sources of information used to collect GIS data are becoming obsolete and outdated The same can be said for the GIS data collected from these sources How can the data and information in a GIS be updated e The accuracy of the source data used to collect GIS data is questionable For example how accurate is the 1960 topographic map used to digitize contour lines e The amount of time required to prepare and collect GIS data from existing sources of information is great e The cost required to prepare and collect GIS data is high For example georectifying 500 photographs to map an entire county may take up to three months which does not include collecting the GIS data Similarly digitizing hardcopy maps is time consuming and costly not to mention inaccurate e Most of the original sources of information used to collect GIS data provide only 2D information
170. hose portions of the image that were blocked by the model Drag each of the yellow vertices so that they roughly overlay the corresponding parts of the Active Image Do not worry about being precise here just roughly estimate the positions on the image We will enlarge the image and fine tune our vertices in a moment Texturizing the Model 224 9 Click the Fit Points to Screen button to resize the view within the workspace 10 To zoom in on the Active Image select the Image Options mode by clicking the Su button on the Texel Mapper toolbar 11 Hold the middle mouse button and drag to zoom in Hold the Left mouse button and drag to pan through the image When fine tuning your vertices it is a good idea to maximize the Texel Mapper display and to zoom in as far as possible on the Active Image This allows you to be more accurate when adjusting the positions of the vertices 12 Click the Affine Map Options button Es to return to the Affine Map mode 13 Middle drag to zoom in on the model It should be large enough to see the effects of moving the vertices and small enough that it does not block your view of any of the corners of the building in the image 14 Uncheck the Wireframe button so you can see the texture as it is mapped on the model 15 Drag the vertices so that they accurately rest on the corresponding building corners in the image As you move the vertices the texture on the model will warp an
171. hree points e average elevation value in a polygon e average elevation value in a polyline The 3D Measure tool can be used as an effective aid for airphoto interpretation and quantitative analysis of geographic information For example the area boundary of a forest can be delineated and measured in 3D Specifically the steps you are going to execute in this example include e Open a block file e Select a DSM from the Stereo Pair Chooser e Open the 3D Measure tool e Measure points polylines and polygons in 3D e Evaluate the measurement results e Save 3D Measure tool results to an ASCII file Stereo Analyst Introduction 147 H Getting Started Open a Block File Stereo Analyst The data used in this tour guide covers the campus of The University of Western Ontario in London Ontario Canada The four photographs were captured at a photographic scale of 1 6000 The photographs were scanned at a resolution of 25 microns The resulting ground coverage per pixel is 0 15 meters Approximate completion time for this tour guide is 1 hour 15 minutes You must have both Stereo Analyst and the example files installed to complete this tour guide NOTE This tour guide was created in color anaglyph mode If you want your results to match those in this tour guide set your stereo mode to color anaglyph by selecting Utility gt Stereo Analyst Options gt Stereo Mode gt Stereo Mode gt Color Anaglyph Stere
172. hwayi 00 e 3D ARC Attributes 3 NUMERIC widt FLOAT width FLOAT width Shapes 1 te Values 000000 9 480000 6 110000 of Parts 1 0 r of Points 7 477567 790655 477590 949369 477640 467529 477682 994049 477835 599716 477780 959225 h 5 numdecs 12 numdecs 12 numdecs 4761334 4761320 4761334 4761370 4761325 4761160 590929 846640 585455 204399 251643 110996 O name iFIDi 253 292 249 249 240 238 2 name iLengthi 2 name iAvg_Zi 274794 083886 732452 981176 026947 303423 ASCII File Example 260 Stereo Analyst 0 000000 6 477770 529141 4761129 603740 239 362935 0 000000 Shape Class 7 iunmonumentedi FCode 1002 Shape Type 3D POINT Number of Attributes 2 0 type NUMERIC width 5 numdecs 0 name iFIDi 1 type FLOAT width 12 numdecs 2 name iAvg Zi Number of Shapes 7 Shape 0 Attribute Values 0 1 000000 1 252 520000 Number of Parts 1 Part 0 Number of Points 1 0 477751 157808 4761643 623624 252 523214 0 000000 Shape 1 Attribute Values 0 2 000000 1 243 360000 Number of Parts 1 Part 0 Number of Points 1 0 477936 028257 4761520 168603 243 360006 0 000000 Shape 2 Attribute Values 0 3 000000 1 230 470000 Number of Parts 1 Part 0 Number of Points 1 0 477960 057966 4761373 735163 230 468465 0 000000 Shape 3 Attribute Values 0 4 000000 1 250 310000 Number of P
173. i 9 and Kappa x Figure 20 illustrates the elements of exterior orientation Figure 21 illustrates the individual angles o o and x of exterior orientation Exterior Orientation 47 Figure 20 Elements of Exterior Orientation Ground Point P Figure 21 Omega Phi and Kappa Z Z y y y Omega Phi Kappa Stereo Analyst Exterior Orientation 48 The Collinearity Equation Stereo Analyst Omega is a rotation about the photographic x axis Phi is a rotation about the photographic y axis and Kappa is a rotation about the photographic z axis which are defined as being positive if they are counterclockwise when viewed from the positive end of their respective axis Different conventions are used to define the order and direction of the three rotation angles Wang 1990 The International Society of Photogrammetry and Remote Sensing ISPRS recommends the use of the o q x convention The photographic z axis is equivalent to the optical axis focal length The x y and z coordinates are parallel to the ground space coordinate system Using the three rotation angles the relationship between the image space coordinate system x y and z and ground space coordinate system X Y and Z or x y and z can be determined A 3 x 3 matrix defining the relationship between the two systems is used This is referred to as the orientation or rotation matrix M The rotation matrix can be defined as follows
174. ids lar_rapids Large Rapids 68 bmp 10005 Polyline Perennial lake per_lake Per Lake 69 bmp 10006 Polygon Intermittent lake int_lake Int Lake 70 bmp 10007 Polygon Pond pond Pond 71 bmp 10008 Polygon Dry lake dry_lake Dry Lake 72 bmp 10009 Polygon Narrow wash narr_wash Narrow Wash 73 bmp 10010 Polyline Wide wash wide_wash Wide Wash 74 bmp 10011 Polyline Well or spring spring or seep well Well water 76 bmp 10012 Point Submerged Areas and Bogs Marsh or swamp marsh Marsh 77 bmp 11000 Polygon Submerged marsh or swamp sub_mar Sub Marsh 78 bmp 11001 Polygon Wooded marsh or swamp wood_marsh Wood Marsh 79 bmp 11002 Polygon Submerged wooded marsh or swamp su_w_marsh Sub W Marsh 79 bmp 11003 Polygon Rice field rice_field Rice Field 80 bmp 11004 Polygon Buildings and Related Features Building 1 building1 Building 1 81 bmp 12000 Polygon Building 2 building2 Building 2 82 bmp 12001 Polygon Building 3 building3 Building 3 83 bmp 12002 Polygon Building 4 building_4 Building 4 84 bmp 12003 Polygon School school School 85 bmp 12004 Polygon Stereo Analyst Default Stereo Analyst Feature Classes 251 Table 9 Stereo Analyst Default Feature Classes Continued Feature Stereo i Feature Feature Class File Analyst Bitmap FCODE Type Name fcl Name Church church Church 86 bmp 12005 Polygon Built up area built up Built Up Area 87 bmp 12006 Polyg
175. ientation and position between the two images Thus once y parallax has been properly minimized the difference between the position and orientation of the two images has been accounted for Example 2 above shows minimized y parallax Since nonoriented DSMs are created without the use of accurate sensor model information y parallax must be minimized throughout various portions of the image while they are being viewed Using oriented DSMs Stereo Analyst uses the accurate sensor model information to automatically minimize y parallax while viewing a given area of interest This process is also referred to as epipolar resampling on the fly The cursor used in Stereo Analyst can also be referred to as the floating cursor It is referred to as a floating cursor because the cursor commonly floats above or below the ground while roaming or panning throughout various portions of the DSM In order to collect accurate 3D geographic information the cursor must rest on the ground or the human made feature that is being collected The floating cursor is the primary measuring mark used in Stereo Analyst to collect and measure 3D geographic information The floating cursor consists of a cursor displayed for the left image and a cursor displayed for the right image The two left and right image cursors define the exact image positions of a feature on the left and right image Thus to take a measurement the location of the cursor on the left image must co
176. ies 255 e Polygon features have a default FID Area Perimeter and AvgZ attribute field e Parallel polyline features have a default FID Length AvgZ and Width attribute field Attribute Description The attribute description fields define the characteristics associated with a given attribute This includes e type of attribute for example floating real integer e width that is number of characters used to store the attribute string e the number of decimal places used to display and store the attribute value if numeric and e name of the attribute The following is an example 0 type NUMERIC width 5 numdecs O name FID 1 type FLOAT width 12 numdecs 2 name Area 2 type FLOAT width 12 numdecs 2 name Perimeter 3 type FLOAT width 12 numdecs 2 name Avg Z In this example the first attribute is FID Its display width is 5 characters and has O decimal places numdecs The second attribute is Area and it has a display width of 12 characters and contains 2 decimal places to the right The third attribute is Perimeter and it has a display width of 12 characters and contains 2 decimal places to the right The fourth attribute is AvgZ and it has a display width of 12 characters with 2 decimal places to the right Number of Shapes This value indicates the number of shapes collected for the specific feature class For example if 20 houses were collected for the residential feature cl
177. iling a representative texture onto the remaining sides Tiling a texture means repeating a simple small pattern across a large area like tiling a floor The Texel Mapper includes a Tile Library for organizing and maintaining your collection of tiles First you add the new texture to the Tile Library Enter the Tile Options mode by clicking the Tile Options icon on the Texel Mapper toolbar The Tile Options dialog displays Create a new Image Class by clicking the Add Class icon a next to the Image Class dropdown list The New Image Class dialog displays Enter Building Sides into the text box and click OK Building Sides appears in the Image Class dropdown list To add an image to the Building Sides class click the Add Image icon ay next to the Image Name dropdown list A File Selector displays Select JFIF from the Files of Type dropdown list Select karolinenplatz_texture jpg from the list of files On the Options tab check No Stretch Click OK The image karolinenplatz_texture is added to the Building Sides Image Class and displays in the Texel Mapper workspace Now you need to tile the image on the model You will start by applying the texture to a several faces Rotate the model so that the rear of the building is visible Select all of the polygons that comprise the rear walls of the building Tiling a Texture 233 tL Do not select these features Select these walls 3 Click the
178. in a different DSM within the western_accuracy blk file 1 Click the Stereo Pair Chooser icon i The Stereo Pair Chooser opens Here you can rapidly select another DSM to view in the Digital Stereoscope Workspace Stereo Analyst Collect a River Feature 205 Select this DSM Click Apply to update the display in the workspace Click in the ID column and select 1 This corresponds to the DSM consisting of the images 251 img and 252 img Click Apply then Close The new DSM displays in the Digital Stereoscope Workspace Open the Position Tool Stereo Analyst Click the Position tool icon in the toolbar of the Digital Stereoscope Workspace The Digital Stereoscope Workspace adjusts to accommodate the Position tool In the Position tool type the value 478144 in the X field then press Enter on your keyboard Type 4760410 in the Y field then press Enter Type 235 09 in the Z field then press Enter Type 0 8 in the Zoom field then press Enter Collect a River Feature 206 Stereo Analyst drives to a bend in a road Just beyond this road is the river bank You start digitizing the river bank from this point 6 Click the Close icon X to close the Position tool and maximize the display area 7 Adjust the x parallax as necessary 4H ET RRP RRS tsat CUO The names of Mos i155 L 0rt iiygmuas3 the new DSM E diea images display here The edge of the DSM is evident in this area
179. in an image by using a combination of the mouse and the X key on your keyboard cl Gk For more information please refer to Adjusting X Parallax on page 103 Position the cursor over the stadium then press and hold the wheel while moving the mouse away from you to zoom in If necessary use the Left Buffer icon Lj and adjust the position of the image to improve the overlap of the images Be sure to deselect it when you are finished adjusting the left image of the stereopair Be sure to deselect the icon when you are finished Adjust and Rotate the Display 94 Stereo Analyst X parallax is evident in X parallax this portion of the has been adjusted image the building features do not overlap NOTE In this portion of the image the X parallax has been exaggerated for the purposes of this tour guide Notice that the left and right images red and blue respectively are not aligning properly This is especially apparent in the parking area where the sidewalks and trees are not on top of one another one appears to be a ghost image of the other Once the left and right images and hence the sidewalks are aligned you can see in stereo Again keep in mind that your perception may differ depending on the mode in which you are viewing the images Quad Buffered Stereo or Color Anaglyph Stereo Hold down the X key on your keyboard while you simultaneously hold down the left mouse button Move the mouse to the l
180. in the x direction is commonly provided with the calibration report that comes with the imagery 6 In the Principle Point yo field type a value of 0 004 then press Enter The principal point offset in the y direction is commonly provided with the calibration report that comes with the imagery For additional information about these parameters see Digital Mapping Solutions Add Interior and Exterior Information for Frame 1 la left img At the bottom of the Frame 1 tab of the Create Stereo Model dialog there are two additional tabs that allow you to provide sensor model information associated with the imagery as it existed when the data was captured These two tabs Interior and Exterior can be updated with information provided by the data vendor The Interior tab allows for the input of the six interior orientation affine transformation coefficients that is a0 al a2 bO bi b2 The Exterior tab allows for the input of the six exterior orientation parameters of the image that is X Y Z Omega Phi Kappa Stereo Analyst Open the Create Stereo Model Dialog Interior and Exterior information is contained in separate tabs pal interes tener bo a0 m LO b1 Do not enter commas into the Interior orientation CellArray 1 Using the following table type the six coefficient values for la left img into the Interior tab Table 5 Interior Orientation Parameters for Frame 1 la le
181. inal left and right images so that the image positions of a ground point do lie along a straight line The image positions of a ground point only lie along a straight line if the varying image orientations and position of each sensor have been considered Once the left and right images have been resampled the epipolar line is parallel to the flight line axis Using OpenGL software techniques Stereo Analyst automatically resamples the left and right images of a stereopair if sensor model information is available If epipolar resampled imagery has already been created in another photogrammetric product a Stereo Analyst STP file can be created in order to use the data and information in Stereo Analyst The Stereo Analyst STP file contains the following information Introductory line This line is required for each Stereo Analyst STP file It states that the information in the file reflects epipolar geometry information Geometry The geometry field defines the type of sensor model used The Stereo Analyst STP file supports frame camera sensor systems only The frame camera sensor system employs single perspective geometry to capture photography and imagery The value to be used for this field is FRAME STP File Characteristics 264 Stereo Analyst Projection Name The STP file format supports a Cartesian based projection system The options include UTM and Cartesian The projection specified should reflect the projection used to determ
182. inate system is usually a coordinate system with its origin in the upper left corner of the image the x axis pointing to the right the y axis pointing downward and the units in pixels as shown by axes c and r in Figure 14 These file coordinates c r can also be thought of as the pixel column and row number respectively Figure 14 Pixel Coordinates and Image Coordinates Origin of pixel coordinate system y Pd r Origin of image coordinate system Scanning Aerial Photography 40 Image Coordinate System An image coordinate system or an image plane coordinate system is usually defined as a 2D coordinate system occurring on the image plane with its origin at the image center The origin of the image coordinate system is also referred to as the principal point On aerial photographs the principal point is defined as the intersection of opposite fiducial marks as illustrated by axes x and y as in Figure 14 Image coordinates are used to describe positions on the film plane Image coordinate units are usually millimeters or microns Image Space Coordinate System Stereo Analyst An image space coordinate system Figure 15 is identical to image coordinates except that it adds a third axis z The origin of the image space coordinate system is defined at the perspective center S as shown in Figure 15 The perspective center is commonly the lens of the camera as it existed when the photograph was captured Its x axis an
183. ine the epipolar resampled imagery and exterior orientation information See the On Line Help for more information about projections Unit X and Y The unit X and Y value should reflect the units associated with the X and Y components of exterior orientation for the left and right images Unit Z The unit Z value should reflect the units associated with the Z component of exterior orientation for the left and right images Resampling Mode The resampling mode value indicates which resampling method was used to perform epipolar resampling on the left and right images A value of 1 is used for nearest neighbor and a value of 2 is used for bilinear interpolation Rotation Angle Mode The rotation angle mode value indicates the type of rotation system used to derive the orientation angles associated with exterior orientation A value of 1 indicates that the Phi about X Omega about Y Kappa about Z system was used A value of 0 indicates that the Phi about X Omega about Y Kappa about Z system was used A value of 2 indicates that the Omega about X Phi about Y and Kappa about Z system was used Average Flying Height The average flying height value defines the average altitude above ground level of the sensor as it existed when the image was captured The units of this value should correspond to the units defined by Unit Z Epipolar Focal Length The epipolar focal length value defines the focal length used dur
184. ing the aerial triangulation process The units used for the focal length should be the same as the units used for the interior orientation affine transform coefficients Output Image File First The output image file first field defines the name of the left image file The STP file supports IMG and TIF image files If the output STP file and the image files are not stored in the same directory the image name and path must be defined Output Image Number First The output image number first field defines the image ID to be used for the left image comprising the stereopair of interest Inner Parameter First The inner parameter first field defines the six affine coefficients computed from the epipolar resampling process associated with the interior orientation of the left image The units of the coefficients should be equivalent to the units used for the focal length The affine transform coefficients should be defined according to the image that is pixel to film format STP File Characteristics 265 a STP File Example Stereo Analyst Outer Parameter First The outer parameter first field defines the six exterior orientation values for the left image which are computed from the epipolar resampling process The units of the positional elements of exterior orientation must be equivalent to the UNIT X Y and UNIT Z definitions Output Image File Second The output image file second field defines the name of the right image file T
185. is already populated with a file la left img This field is automatically populated with the first image you choose when you initially open the Digital Stereoscope Workspace 2 Confirm that the Interior Affine Type is set to Image to Film Stereo Analyst Open the Create Stereo Model Dialog 121 The interior affine type defines the convention used to display the six coefficients that describe the relationship between the image and film coordinate systems The image coordinate system is defined in pixels while the film that is photo coordinate system can be defined in millimeters microns etc The options include Image to Film and Film to Image The Image to Film option describes the six affine transform coefficients going from pixels to linear units such as millimeters or microns The Film to Image option describes the six affine transform coefficients going from linear units to pixels The option you select defines how the six values are entered into the Create Stereo Model dialog 3 Confirm that the Camera Units are set to Millimeters The camera units should correspond to the camera calibration values used for focal length and principal point in the x and y direction 4 Inthe Focal Length field type a value of 154 047 then press Enter on your keyboard The focal length of the camera is provided with the calibration report 5 In the Principle Point xo field type a value of 0 002 then press Enter The principal point offset
186. itions with the 3D Measure tool is advantageous for collecting information in specific geographic areas where automated techniques fail This includes floodplains drainage networks dense urban areas forested areas and road and highway networks including bridges This approach is also beneficial for collecting 3D information in areas which are normally not accessible by a field survey team Thus using Stereo Analyst highly accurate 3D point positions can be collected in an office environment Enter the 3D Coordinates 1 Click the Zoom 1 1 icon Z 2 In the Position tool double click in the X field and type 477745 03 3 In the Y field type 4761435 21 4 In the Z field type 268 25 Digitize the 3D Positions Stereo Analyst drives to the 3D coordinate position you specify The roof of this building is divided into many sections and elevations You can begin digitizing roof corners at the topmost roof the one that houses the heating and air conditioning equipment Start digitizing with this roof 1 Adjust the x parallax and the 3D cursor elevation as necessary 2 In the 3D Measure tool click to select the Points tool 3 Click the Unlock icon E so that it becomes the Lock icon T You can then collect consecutive 3D points Stereo Analyst Take 3D Measurements 166 10 Position your cursor at one corner of the roof that houses the utility equipment Adjust the x parallax and cursor elevatio
187. ity Equations f For each measured GCP there are two corresponding image coordinates x and y Thus two collinearity equations can be formulated to represent the relationship between the ground point and the corresponding image measurements In the context of bundle block adjustment these equations are known as observation equations If a GCP has been measured on the overlapping area of two images four equations can be written two for image measurements on the left image comprising the pair and two for the image measurements made on the right image comprising the pair Thus GCP A measured on the overlap area of image left and image right has four collinearity formulas mi XX mpo Y4 Y mjy1Z Z m i Xa X m3 Y Y m3 ZA Z mj XX mo YA Y mo3 Z4 Z m34 X X t mo5 Y Y m3 ZA Zo 1 ll ASS Saf m X X tmil a Y tma Zo m3 Xa X m32 Y Y m 3 Z4 Zo f m X4 X m5 Y Y m3 Z4 Zo m 4 X X t m Y Y t m 3 Z4 Zo One image measurement of GCP A on Image 1 Xap Ya One image measurement of GCP A on Image 2 Xay Ya Positional elements of exterior orientation on Image 1 Xop Yap Zo Positional elements of exterior orientation on Image 2 As Vowel 05 05 05 Digital Mapping Solutions 55 Least Squares Adjustment Stereo Analyst If three GCPs have been measured on the overlap area of two images twelve equatio
188. l and the method you choose will depend upon the orientation of the feature of interest in your imagery The first method of texturization that we will use is called the Affine Map Mode This mode will directly map a portion of the image onto the model It works best with head on photographs that have little or no perspective distortion You may want to maximize the Texel Mapper window on your screen so that you have a lot of workspace in which to manipulate the model and images In the Active Image popup list select karolinenplatz front The karolinenplatz front jpg image displays behind the model Texturizing the Model 223 Stereo Analyst Click and drag the cursor in the workspace to rotate the model so that the front of the model displays Click the Affine Mapping button Es to enter Affine Map Options mode The Affine Map Options dialog displays Right click on the front face of the model to select one of the polygons Ctrl right click on the other half of the face to select the entire front polygon The selected face of the model is now tiled with a texture and the vertices of the selected faces have yellow lines that extend off of the viewable area of the workspace Click the Fit Points to Screen button on the Affine Map Options dialog The image is resized so that all four vertices are fit inside the viewable Workspace Check the Wireframe checkbox The model displays without any textures Now you can see t
189. l key and the left mouse button simultaneously This adjusts cursor elevation x left designates holding the x key on the keyboard and the left mouse button simultaneously while moving the mouse left and right This adjusts x parallax y left designates holding the y key on the keyboard and the left mouse button simultaneously while moving the mouse up and down This adjusts y parallax c left designates holding the c key on the keyboard and the left mouse button simultaneously while moving the mouse up and down This adjusts cursor elevation For the purpose of completing the tour guides in this manual we assume that you are using a mouse equipped with a rolling wheel where the middle mouse button usually exists You use this wheel to zoom into more detailed areas of the image displayed in the stereo views If your mouse is not equipped with a rolling wheel then you can use the middle mouse in the same context except where noted t Left mouse button 4 J oy gt i Rolling wheel or middle mouse butto m e E Right mouse button Conventions Used in This Book xv Paragraph Types The following paragraphs are used throughout this book These paragraphs contain strong warnings or important tips These paragraphs direct you to the ERDAS IMAGINE or Stereo Analyst software function that accomplishes the described task These paragraphs lead you to other areas of this book or other Leica Geosystems
190. le block adjustment may include the internal sensor model information external sensor model information the 3D coordinates of tie points and additional parameters characterizing the sensor model This output is commonly provided with detailed statistical reports outlining the accuracy and precision of the derived data For example if the accuracy of the external sensor model information is known then the accuracy of 3D GIS data collected from this source data can be determined You can learn more about the bundle block adjustment method in Photogrammetry Rather than manually collecting individual 3D point positions with a GPS or using direct 3D measurements on imagery automated techniques extract 3D representations of the surface of the Earth using the overlap areas of two images This is referred to as automated DTM extraction Digital image matching that is auto correlation techniques are used to automatically identify and measure the positions of common ground points appearing within the overlap area of two adjacent images Workflow 24 Orthorectification 3D Feature Collection and Attribution Stereo Analyst Using sensor model information determined from bundle block adjustment the image positions of the ground points are transformed into 3D point positions Once the automated DTM extraction process has been completed a series of evenly distributed 3D mass points is located within the geographic area of intere
191. lection of geographic information Using digitally scanned photographs Stereo Analyst allows for the rotation scaling and translation of overlapping images for the creation of a clear 3D DSM Once a DSM has been created the following are some of the geographic characteristics that can be determined using airphoto interpretation techniques in Stereo Analyst land use land cover tree type bedrock type landform type soil texture site drainage conditions susceptibility to flooding depth of unconsolidated materials over bedrock and slope of land surface This tour guide leads you through the process of using Stereo Analyst to create a clear 3D stereo view for airphoto interpretation applications Specifically the steps you are going to execute in this example include e Select a mono image that represents the left image comprising a DSM e Adjust the display resolution e Apply Quick Menu options e Select a second image for stereo that represents the right image comprising a DSM e Orient and rotate the images e Adjust parallax e Position the 3D floating cursor e Adjust cursor elevation e Save the DSM e Open the new DSM Stereo Analyst Introduction 75 BE Getting Started Launch Stereo Analyst Adjust the Digital Stereoscope Workspace Stereo Analyst The data you are going to use in this example is of Los Angeles California The data is continuous 3 band data with an approximate ground resolution of
192. led in the Options dialog under the Cursor Height and Adjustment Option Category In this mode regardless of where you are in the image the cursor maintains the same elevation You can view actual elevations in the window by deselecting this option Now that you know how to adjust x parallax y parallax and cursor elevation you can practice using the methods you have learned in other areas of the image First you zoom into and out of areas of the image You can then use the OverView and Left and Right Views to see features Hold down the wheel and push the mouse away from you that is up and down This motion zooms into a more detailed portion of the stereopair Continue to zoom in until you can see a sufficiently detailed area Toroam hold down the left mouse button and drag the stereopair in the window to the right and or left until you find an area that interests you such as the following Zoom out by clicking and holding the wheel and pull the mouse toward you You can see a larger portion of the stereopair in the view Click the 1 1 Resolution icon gl Practice Using Tools 100 The stereopair displays in the Digital Stereoscope Workspace at a 1 1 resolution image pixel to screen pixel Therefore one image pixel equals one screen pixel 6 Adjust the x parallax and the Y parallax as necessary 7 Click the view Full Extent icon Ez a ip ime rap 7 Ww wen eke REC w ar cuc CCO u Le k 55 Oo OE
193. lishing Company Schenk T 1997 Towards automatic aerial triangulation ISPRS Journal of Photogrammetry and Remote Sensing 52 3 110 121 Stojic M et al 1998 The assessment of sediment transport rates by automated digital photogrammetry PE amp RS Vol 64 No 5 pp 387 395 Tang L J Braun and R Debitsch 1997 Automatic aerotriangulation concept realization and results ISPRS Journal of Photogrammetry and Remote Sensing Vol 52 pp 121 131 Tsingas V 1995 Operational use and empirical results of automatic aerial triangulation Proceedings of 45th Photogrammetric Week Wichmann Verlag Karlsruhe pp 207 214 Vosselman G and N Haala 1992 Erkennung topographischer PaBpunkte durch relationale Zuordnung Zeitschrift f r Works 272 Stereo Analyst Photogrammetrie und Fernerkundung 6 170 176 Wang Y 1988 A combined adjustment program system for close range photogrammetry Journal of Wuhan Technical University of Surveying and Mapping Vol 12 No 2 1994 Strukturzuordnung zur automatischen Oberfl chenrekonstruktion Ph D dissertation wissenschaftliche Arbeiten der Fachrichtung Vermessungswesen der Universit t Hannover No 207 1998 Principles and applications of structural image matching ISPRS Journal of Photogrammetry and Remote Sensing Vol 53 pp 154 165 Wang Z 1990 Principles of photogrammetry with Remote Sensing Press of Wuhan Te
194. lustrates the concept associated with space forward intersection NOTE This concept is key for the determination of 3D ground coordinate information in Stereo Analyst Figure 22 Space Forward Intersection O1 Zol Zo2 M Ground Point P Digital Mapping Solutions 52 Bundle Block Adjustment Stereo Analyst Space forward intersection techniques assume that the exterior orientation parameters associated with the images are known Using the collinearity equations the exterior orientation parameters along with the image coordinate measurements of point p1 on Image 1 and point p2 on Image 2 are input to compute the Xp Yo and Zp coordinates of ground point P Space forward intersection techniques can also be used for applications associated with collecting GCPs cadastral mapping using airborne surveying techniques and highly accurate point determination For mapping projects having more than two images the use of space intersection and space resection techniques is limited This can be attributed to the lack of information required to perform these tasks For example it is fairly uncommon for the exterior orientation parameters to be highly accurate for each photograph or image in a project since these values are generated photogrammetrically Airborne GPS and INS techniques normally provide initial approximations to exterior orientation but the final values for these parameters must be adjusted to attain highe
195. mage the geometry associated with the camera sensor image and ground can be defined to greater accuracies Image and Data Acquisition 35 During the collection of imagery each point in the flight path at which the camera exposes the film or the sensor captures the imagery is called an exposure station see Figure 10 and Figure 11 Figure 10 Exposure Station The photographic exposure station is _ located where the image is exposed the lens Figure 11 Exposure Stations Along a Flight Path Flight path Flight Line 3 e e e e e gt of airplane Flight Line 2 Flight Line 1 Stereo Analyst O Exposure station Each photograph or image that is exposed has a corresponding image scale SI associated with it The SI expresses the average ratio between a distance in the image and the same distance on the ground It is computed as focal length divided by the flying height above the mean ground elevation For example with a flying height of 1000 m and a focal length of 15 cm the SI would be 1 6667 NOTE The flying height above ground is used to determine SI versus the altitude above sea level A strip of photographs consists of images captured along a flight line normally with an overlap of 60 All photos in the strip are assumed to be taken at approximately the same flying height and with a constant distance between exposure stations Camera tilt relative to the vertical is assumed to be minimal
196. mage of the stereopair When the stereopair is viewed in stereo the two floating marks display as one when x parallax is reduced Focal length The distance between the optical center of the lens and where the optical axis intersects the image plane Focal length of each camera is determined in a laboratory environment GCP See Ground control point Geocentric A coordinate system with its origin at the center of the Earth ellipsoid The Z axis equals the rotational axis of the Earth the X axis passes through the Greenwich meridian and the Y axis is perpendicular to both the Z axis and the X axis so as to create a 3D coordinate system that follows the right hand rule Geocorrect A method of establishing a geometric relationship between imagery and the ground Geocorrection does not use many GCPs and is therefore not as accurate as orthocorrection or orthorectification See also Orthorectify Geolink A method of establishing a relationship between attribute data and the features they pertain to Global Positioning System GPS A system for determining position on the Earth s surface by comparing radio signals from satellites FOLDOC 2000b GPS See Global Positioning System Ground control point GCP A specific pixel in image data for which the output map coordinates or other output coordinates are known GCPs are used for computing a transformation matrix for use in rectifying an image Ground coordinate space A co
197. mation coefficients The resulting six coefficients can then be used to transform each set of row y and column x pixel coordinates to image coordinates The quality of the 2D affine transformation is represented using a root mean square RMS error The RMS error represents the degree of correspondence between the calibrated fiducial mark coordinates and their respective measured image coordinate values Large RMS errors indicate poor correspondence This can be attributed to film deformation poor scanning quality out of date calibration information or image mismeasurement The affine transformation also defines the translation between the origin of the pixel coordinate system and the image coordinate system Xo file and Yo file Additionally the affine transformation takes into consideration rotation of the image coordinate system by considering angle O A scanned image of an aerial photograph is normally rotated due to the scanning procedure The degree of variation between the x axis and y axis is referred to as nonorthogonality The 2D affine transformation also considers the extent of nonorthogonality The scale difference between the x axis and the y axis is also considered using the affine transformation NOTE Stereo Analyst allows for the input of affine transform coefficients for the creation of a DSM in the Create Stereo Model tool Lens distortion deteriorates the positional accuracy of image points located on the image pl
198. may need to zoom in to see it clearly Use Selection Criteria You can use some of the ERDAS IMAGINE tools such as Selection Criteria to extract meaningful information from the attribute table 1 Right click in the ID column to open the Row Selection menu 2 Choose Select All from the Row Selection menu The rows are highlighted in the attribute table Stereo Analyst Check Attributes 217 Highlighted rows gea imbu are selected 3 Right click in the 1D column and select Criteria from the Row Selection menu The Selection Criteria dialog opens Click Select to see the features iss with this criteria fina 200 Sce sue Me Ow e The formula displays here as you create it 4 In the Columns section of the dialog click Area 5 In the Compares section of the dialog click the greater than sign gt 6 Click 2000 in the number pad then click Select at the bottom of the dialog The features with areas greater than 2000 are highlighted in the attribute table and in the Digital Stereoscope Workspace Your results may differ from those presented here am E 222 AER Features 1 and 3 meet the criteria you specified 7 Click Close in the Selection Criteria dialog 8 Right click in the ID column of the Building 1 attribute table and click Select None Stereo Analyst Check Attributes 218 Check the Woods Attributes As you continue to open attribute tables associated with your features the
199. means that the cursor is not positioned on the ground Also if you look at the Left and Right Views containing the left and right images of the DSM you see that the cursor does not appear to be in the same geographic location in both images Stereo Analyst Take 3D Measurements 155 Stereo Analyst These cursors are not in the same exact location NOTE The optimum zoom rate for collecting 3D measurement for this particular area of interest is 1 5 You can enter this value in the Position tool Adjust the height of the 3D floating cursor so that the cursor rests on the ground NOTE This does not affect the selection of the Polyline tool Ifyou do not have a mouse equipped with a wheel you can hold the C key on the keyboard as you simultaneously hold the left mouse button Then move the mouse forward and away from or backwards and toward you to adjust elevation Click the left mouse button to digitize the first vertex associated with the polyline Move vertically along the sidewalk and continue to click to place vertices along the edge of the sidewalk NOTE Ensure that the 3D floating cursor rests on the ground at each point of measurement NOTE As you approach the display extent of the Main View the image automatically roams so that you can continue digitizing The area outside the visible space is called the autopan buffer Stereo Analyst recognizes when your cursor is in the autopan buffer and
200. most of your tasks here entire DSM and zoom here you the individual images in the stereopair a Load the LA Data Stereo Analyst Move your mouse over the bar between the Main View and the OverView and Left and Right Views It becomes a double headed arrow Drag the bar to the right and or left to resize the Main View OverView Left and Right Views The data you are going to use for this tour guide is not located in the examples directory Rather it is included on a data CD that comes with the Stereo Analyst installation packet To load this data follow the instructions below Insert the Stereo Analyst data CD into the CD ROM drive Open Windows Explorer Load the LA Data 77 Open the Left Image Stereo Analyst Select the files la_left img and la_right img and copy them to a directory on your local drive where you have write permission Ensure that the files are not read only by right clicking to select Properties then making sure that the Read only Attribute is not checked A nonoriented DSM provides a 3D representation when viewed in stereo but does not provide absolute real world geographic coordinates The images comprising a nonoriented DSM have not been geometrically oriented and aligned using accurate sensor model information As a result you must rotate scale and adjust the images while viewing different portions of the nonoriented DSM The two images comprising the nonoriented DSM must be adjusted a
201. n inventory and so forth e Urban change detection studies use photography collected from various time periods for analyzing the extent of urban growth Land use and land cover information is categorized for each time period and subsequently compared to determine the extent and nature of land use land cover change Water Resource Management DSMs are a necessary asset for monitoring the quality quantity and geographic distribution of water The 3D information collected from DSMs is used to provide descriptive and quantitative watershed information for a GIS Various watershed characteristics can be derived from DSMs including terrain type and extent surficial geology river or stream valley characteristics river channel extent river bed topography and terraces Individual river channel reaches can be delineated in 3D providing an accurate representation of a river Rather than manually survey 3D point information in the field highly accurate 3D information can be collected from DSMs to estimate sediment storage river channel width and valley flat width Using historical photography 3D measurements of a river channel and bank can be used to estimate rates of bank erosion deposition identify channel change and describe channel evolution disturbance Telecommunications Stereo Analyst The growing telecommunications industry requires accurate 3D information for various applications associated with wireless telecommunications
202. n as necessary Click to digitize the first corner Continue to digitize the corners of the roof NOTE Ensure that the 3D floating cursor is positioned on the feature of interest during the collection of 3D point positions Move to another roof section adjust the x parallax and cursor elevation Click to digitize the corners of that roof Continue to move to different sections of the roof digitizing the corners until you have digitized all the corners of the entire roof Evaluate Results Stereo Analyst As the roof corners are digitized the measurements are reported in the text field of the 3D Measure tool JO Manus Tool TIK CM e 2 Point features are listed sequentially NOTE Your results may differ from those presented here Use the scroll bar to see the first line of data associated with the polyline you just digitized Point 1 Pt 1 476892 218006 4761342 010865 meters 254 3793 meters This means that Point 1 has an approximate elevation of 267 meters Notice that the subsequent three points all part of the same roof have similar elevations Take 3D Measurements 167 E Save the Measurements Stereo Analyst JO Means Tool ld Ub oH GE Eo X o co PATA AAN PAL masas 2244 E nacer Dela 2 4 CEE reten Sopa 0120 Apes 161 DED dese LLL AO made 24 SU matar 3 QUH ros e 10 diri VEIA donc ATESC 525 4761232 25 iii EE 74711 Arama Tl DOR 35177 guter 254 154 inet e pe 2 71 1H frau 155
203. nalyst First we must load a 3D model similar to those we collected in Stereo Analyst Click the Open button next to the Active Model dropdown list A File Selector opens Navigate to the lt IMAGINE_HOME gt examples directory Select Multigen OpenFlight from the Files of Type dropdown list Select karolinerplatz flt from the list of files and click OK The building displays in the Texel Mapper workspace Loading the Data Sets 222 In Target mode dragging allows you to rotate the model in the X and Y directions while middle dragging lets you zoom towards and away from the selected model Loading the Textures B Texturizing the Model Texturize a Face In Affine Map Mode Stereo Analyst The textures used in this tour are pictures of the actual building that have been taken with a digital camera Click the Open button ua next to the Active Image dropdown list A File Selector opens Navigate to the IMAGINE HOME examples directory Select JFIF jpg from the Files of type dropdown list Ctrl click karolinenplatz front jpg karolinenplatz left jpg and karolinenplatz right jpg to select them Click the Options tab Set the band combination to Red 1 Green 2 and Blue 3 Check the No Stretch checkbox Click OK All three images are loaded in the background of the Texel Mapper workspace You are now ready to texturize the model There are numerous ways to map textures onto the faces of the mode
204. nalyst coordinates 42 Geocorrect 281 Geolink 14 281 Geometric Properties icon 7 Geometry 264 Global Positioning System 281 GPS 281 Ground control point GCP 281 Ground coordinate space 281 Ground coordinate system 42 281 Ground space 40 281 Ground based photographs 34 H Header file 282 I Icons 3D Extend 9 3D Measure Tool 7 Add Element 9 Box Feature 8 Choose Stereopair 6 Clear View 6 Copy 8 Create Stereo Model 7 Cursor Tracking 6 Cut 8 Fit Scene 6 Fixed Cursor Mode 7 Geometric Properties 7 Image Information 6 Invert Stereo 7 Left Buffer 8 Lock 8 New 6 Open Workspace 6 Orthogonal 8 Parallel 9 Paste 8 Polygon Close 9 Polyline Extend 9 Position Tool 7 Remove Segments 9 Reshape 9 Revert to Original 6 Right Buffer 8 Rotate 8 Save 6 Select Element 9 Streaming 9 Unlock 8 Update Scene 7 Index 292 Zoom one to one 6 Image coordinate space 282 Image coordinate system 41 Image Information icon 6 Image scale 36 282 Image space 40 45 282 coordinate system 41 Inactive tool 282 Indian Remote Sensing Satellite 282 Inertial navigation system 282 Inner parameter first 265 Inner parameter second 266 INS 53 282 Interior Affine Type 121 Interior orientation 44 282 International Society of Photogrammetry and Remote Sensing 282 Interpretative photogrammetry 34 Introductory line 264 Invert Stereo icon 7 IRS 282 ISPRS 282 K Kappa 43 49 275 282 L Landsat 282 Least squares adjustment 53 56 282
205. nalyst wes analyst wes analyst wes i nul Ler Ler Ler Ler cer Ler Ler ter Ler Ler Der Ler Cer CEE Ler cer Cer Ler CEE Ler n_campu pu pu pu pu pu pu pu pu pu pu pu pu pu pu pu pu pu pu pu n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam n_cam 1 i 0 i nul 1 i data western western block2 blk s dual hwy m fcl s second hwy fcl s bridge fcli s light_rd fcli s ind_cont fcl s inter_cont s sup_cont fcli s int_river fcl s int_stream fc s per_river fcl s buildingl fcl s building2 fcl s building3 fcl s building_4 fcl1 s race fcli s church fcli s dual_hwy fcli mp mp gt id cut E 1 1 po i s vineyard fcli s orchard fcli s woods fcli id stereo analyst stereo analyst SceneData ilayernamei id stereo analyst stereo analyst iblocki data western wester iblockfilenamei id stereo ana analyst ileftstretc ileftnumtotalbandsi data western wester himagei ili ilef ili n_block2 b1k1 ilayertypei lyst stereo n block2 blki tinvertcolors 101 ileftnumdisplaybandsi 111 101 Stereo Analyst data wester irightinver irightnumdi id stereo data wester n 253 img irigh tcolors 101
206. ndard gauge single track station rail_single Railroad Single 113 bmp 14000 Polyline Standard gauge multiple track mult_rail Multiple Railroad 114 bmp 14001 Polyline Railroad in street rail_street Rail in Street 119 bmp 14002 Polyline Transmission LInes and Pipelin es Stereo Analyst Default Stereo Analyst Feature Classes Table 9 Stereo Analyst Default Feature Classes Continued Feature Stereo Feature Feature Class File Analyst Bitmap FCODE Type Name fcl Name yP Power transmission line pole tower power_line Power Line 120 bmp 15000 Polyline Telephone line tele_line Telephone Line 121 bmp 15001 Polyline Aboveground oil or gas pipeline ab_gas Above Gas Line 122 bmp 15002 Polyline Underground oil or gas pipeline under_gas Under Gas Line 123 bmp 15003 Polyline Stereo Analyst Default Stereo Analyst Feature Classes 253 Stereo Analyst Default Stereo Analyst Feature Classes Using Stereo H Introduction H ASCII Categories Introductory Text Number of Classes Shape Class Number FCODE Shape Type Analyst ASCII Files American Standard Code for Information Interchange ASCII files containing GIS feature and attribute information can be both imported into and exported from Stereo Analyst In order to import an ASCII file the input ASCII file must conform to the standards defined by Stereo Analyst ESRI 3D Shapefiles c
207. nimal Tangential lens distortion Distortion that occurs at right angles to the radial lines from the principal point Terrestrial photographs Ground based photographs and images taken with a camera stationed on or near the surface of the Earth Photographs are usually used for archeology geomorphology and civil engineering Texels Texture pixels used to determine filtering and texturing Screen pixels per texture pixels Texture map A chunk of image data that can be warped and stretched in three dimensions to fit a set of coordinates specified for the corners Theodolites A surveyor s instrument for measuring horizontal and usually also vertical angles Merriam Webster OnLine Dictionary 2000b Three dimensional See 3D Terms 287 Stereo Analyst Tie point A point whose ground coordinates are not known but can be recognized visually in the overlap or sidelap area between two images TIN see Triangulated Irregular Network Topocentric A coordinate system that has its origin at the center of the image projected on the Earth ellipsoid The three perpendicular coordinate axes are defined on a tangential plane at this center point The plane is called the reference plane of the local datum The x axis is oriented eastward the y axis northward and the z axis is vertical to the reference plane up Transparency Transparency is used in traditional photogrammetry techniques as a method of collecting features It i
208. ns can be formulated which include four equations for each GCP Additionally if six tie points have been measured on the overlap areas of the two images twenty four equations can be formulated which include four for each tie point This is a total of 36 observation equations The previous scenario has the following unknowns e Six exterior orientation parameters for the left image that is X Y Z Omega Phi Kappa e Six exterior orientation parameters for the right image that is X Y Z Omega Phi Kappa and e X Y and Z coordinates of the tie points Thus for six tie points this includes eighteen unknowns six tie points times three X Y Z coordinates The total number of unknowns is 30 The overall quality of a bundle block adjustment is largely a function of the quality and redundancy in the input data In this scenario the redundancy in the project can be computed by subtracting the number of unknowns 30 by the number of knowns 36 The resulting redundancy is six This term is commonly referred to as the degrees of freedom in a solution Once each observation equation is formulated the collinearity condition can be solved using an approach referred to as least squares adjustment Least squares adjustment is a statistical technique that is used to estimate the unknown parameters associated with a solution while also minimizing error within the solution Least squares adjustment techniques are used to e E
209. nter point principal point of each image Adjust and Rotate the Display 88 Orient the Images Stereo Analyst Left image Right image x x X Fiducial Center Fiducial po ui Principal Point o x x x x The center point of the image is also referred to as the principal point The center point of each image can be visually identified by intersecting the corner points that is fiducials of the images When you visually record the center point of each image you note whether it is a house building road intersection tree etc Visually identify the feature located at the center point in the left image la left img Visually identify the same feature on the right image la right img The common feature on the left image should be approximately parallel to the same feature on the right image Thus the same feature on the left and right images should be separated only along the x direction and not the y direction If the common feature is not parallel on the left and right images the images must be rotated Consult the following diagram y y Leftimage Right image Given the existing orientation of the images the common stadium feature is not parallel You have to adjust the images in the e y direction to superimpose the stadium X Now that you have determined that these images are not properly oriented for stereo viewing you may be asking yourself How do
210. ntersection of the two roof lines Once you have determined the correct X and Y position select the Enable Update option once again to disable that capability Record the new X and Y coordinate positions displayed in the Position tool To determine the offset associated with the original X and Y coordinate values subtract the old values from the new values The resulting values indicate the accuracy of the DSM in the X and Y direction over a specific point Determining Stereo Model Accuracy X and Y Coordinates The best way to determine the accuracy of a DSM is to compare your results with coordinates provided to you The following Original coordinates correspond to the first check point You supply the New check point coordinates as you perceive them in the Digital Stereoscope Workspace The difference between them is the accuracy value In this example the accuracy is quite good Original Check E Point 1 debate ds Difference Coordinates X 478221 57 X 478221 3923 0 18 Y 4761174 72 Y 4761174 7167 0 0033 Compute Z Elevation Accuracy Stereo Analyst 1 Place the 3D cursor over the feature of interest The 3D floating cursor should be located within the center point of the crosshair Ensure that the X and Y location of the 3D floating cursor remains at the intersection of the two roof lines If the 3D cursor is not resting on the roof adjust the floating cursor by rolling the mouse wh
211. ntly researching various approaches for eliminating the need to enter a tie point value Click the Clear Viewer icon amp Select File gt Exit Workspace to close Stereo Analyst if you wish In the next tour guide the Position tool is used to verify the quality and accuracy associated with an oriented DSM 3D check points having X Y and Z coordinates are used to independently check the accuracy of a DSM The 3D Position tool can also be used to determine the 2D and 3D accuracy of a GIS layer that is stored as an ESRI Shapefile Next 127 Stereo Analyst Next 128 Checking the Accuracy of a DSM Introduction This tour guide describes the techniques used to determine the accuracy of a DSM Using 3D X Y Z check points the accuracy of an oriented DSM can be determined Similarly using 3D check points the accuracy of GIS layers can also be determined The Position tool in Stereo Analyst is used to enter 3D check point coordinates which are then compared to the position displayed in the 3D stereo view If the check point is correct the 3D floating cursor should rest on the feature or object of interest If the check point is incorrect the following characteristics may be apparent e The 3D floating cursor may be offset in the X and or Y direction e The 3D floating cursor may be positioned above the feature or object e The 3D floating cursor may be positioned below the feature or object If a check point is inco
212. o First you must launch Stereo Analyst For instructions on launching Stereo Analyst see Getting Started Once Stereo Analyst has been started and you have an empty Digital Stereoscope Workspace you are ready to begin y For the remainder of the tour guide you need either red blue glasses or stereo glasses that work in conjunction with an emitter First you open a block file From the toolbar of the empty Digital Stereoscope Workspace click the Open icon ua f The Select Layer To Open dialog opens Here you select the type of file you want to open in the Digital Stereoscope Workspace Open a Block File 148 Select Layer To pen Select the file western accuracy blk Select block file Filename nie tc Ek from the dropdown list Fieri ed tpe MAGNE DeheBA SE Block Fla bak Te amp Apenas esi Aa e UT aln oen her ntis iure bl 2 Navigate to the IMAGINE HOME examples Western directory then select the file named western accuracy blk The block file contains all of the necessary information required to automatically create and display a DSM in real time The block file in this example was created in LPS Project Manager Camera calibration and GCP information was input and used to calculate all of the necessary sensor model information The resulting sensor model information is used to calculate and display 3D coordinate information For more information about the workflow requi
213. o approximately 1 0 2 In the Position tool type the following X Y and Z values respectively 477532 93 4761699 51 and 292 08 Stereo Analyst Use the Position Tool 143 3 Position the cursor and visually interpret the location of the 3D floating cursor over the feature Compute X Y Coordinate and Z Elevation Accuracy 1 If necessary adjust the image so that the feature is within the crosshair using the Enable Update option in the Position tool 2 Record the new X and Y coordinate positions then subtract the old values from the new values to determine accuracy 3 If necessary adjust the height of the cursor 4 Record the new Z coordinate then subtract the old value from the new value to determine accuracy Seventh Check Point 1 Check that Enable Update button is not active and the Zoom is set to approximately 1 0 2 In the Position tool type the following X Y and Z values respectively 478102 12 4761488 28 and 242 60 Stereo Analyst Use the Position Tool 144 3 Position the cursor and visually interpret the location of the 3D floating cursor over the feature Compute X Y Coordinate and Z Elevation Accuracy 1 H Close the Position Tool Stereo Analyst If necessary adjust the image so that the feature is within the crosshair using the Enable Update option in the Position tool Record the new X and Y coordinate positions then subtract the old values from
214. ocesses commonly associated with digital photogrammetry The data and information required for building and maintaining a 3D GIS includes orthorectified imagery DTMs 3D features and the nonspatial attribute information associated with the 3D features Through various processing steps 3D GIS data can be automatically extracted and collected from imagery From Imagery to a 3D GIS 21 Imagery Types E Workflow Stereo Analyst Digital photogrammetric techniques are not restricted as to the type of photography and imagery that can be used to collect accurate GIS data Traditional applications of photogrammetry use aerial photography commonly 9 x 9 inches in size Technological breakthroughs in photogrammetry now allow for the use of satellite imagery digital camera imagery videography and 35 mm camera photography In order to use hardcopy photographs in a digital photogrammetric system the photographs must be scanned or digitized Depending on the digital mapping project various scanners can be used to digitize photography For highly accurate mapping projects calibrated photogrammetric scanners must be used to scan the photography to very high precisions If high end micron accuracy is not required more affordable desktop scanners can be used Conventional photogrammetric applications such as topographic mapping and contour line collection use aerial photography With the advent of digital photogrammetric systems applications
215. ode to color anaglyph by selecting Utility gt Stereo Analyst Options gt Stereo Mode Stereo Mode Color Anaglyph Stereo First you must launch Stereo Analyst For instructions on launching Stereo Analyst see Getting Started Once Stereo Analyst has been started and you have an empty Digital Stereoscope Workspace you are ready to begin The first step in collecting features from a DSM involves setting up the new Digital Stereoscope Workspace From the File menu of the empty Digital Stereoscope Workspace select New Stereo Analyst Feature Project The Feature Project dialog opens In this dialog you select the properties of your feature project including name classes and the associated DSM To create a Feature Project the first tab you enter information into is the Overview tab Feature Project Cheever Festina Clases Shes Moda Propi Haime Fes Other Stereo Analyst feature project files display here Stereo Analyst PATA i Toxurlusde Ul angie 20 Agai X E sn one Type a description of the feature project here 1 Navigate to a directory where you have write permission Create a New Feature Project 172 Enter Information in the Features Classes Tab First you select a feature class Category Click the check boxes to select the type of features to digitize You can also create custom classes By default the Feature Project dialog opens in the directory you
216. ol 152 Take the First Measurement 154 Take the Second Measurement 160 Take the Third Measurement evens 162 Take the Fourth Measurement s s 164 Take the Fifth Measurements eves 165 Save the Measurements 5 168 NeXU uuo Lo r ca Rm m RR RLW cm Uni as TR TR a Tm n 169 Table of Contents vi Collecting and Editing 3D GIS Data 171 Texturizing 3D Models Introduction ee 171 Getting Started cnn 172 Create a New Feature Project 172 Enter Information in the Overview Tab 172 Enter Information in the Features Classes Tab 173 Enter Information into the Stereo Model 179 Collect Building Features 183 Collect the First Building less 183 Collect the Second Building 189 Collect the Third Building lt lt 195 Collect Roads and Related Features 198 Collect a Sidewalk 0 0 ooo 198 Collect a Road 2 elle 201 Collect a River Feature ss 205 Collect a Forest Feature 208 Collect a Forest Feature and Parking Lot 210 Check Attributes es 216 Next x53 eae dew RE IR Eun a as a 220 221 Introduction lees 221 Getting Started cnn 221 Explo
217. olyline feature attributes define the attributes to be used for the specific polyline feature class The following information is used to characterize each polyline feature attribute type of polyline feature attribute STRING INTERGER FLOAT DATE maximum width of attribute display and Stereo Analyst Feature Classes 246 Polygon Feature Class Stereo Analyst number of decimal places used to display the attribute The following feature class provides an example of a Dual Highway polyline feature class FeatureClass iDual Highwayi Category iRoads and Related Features IconFile 1105 bmp1 FeatureCode 13005 FeatureShape POLYLINE PolylineDrawAttributes Color 1 00 0 00 0 00 LineWidth 2s FeatureAttributes iFIDi INTEGER 5 0 iLengthi FLOAT 1 22 iAvg Z FLOAT 12 2 A Stereo Analyst feature class file fcl for a polygon feature contains the following information Feature Class See General Information Category Icon File Feature Code Feature Shape The feature shape describes the shape POLYGON Polygon Display Attributes and The polygon display attributes characterize the fill color opacity border color and border width used to display the polygon feature in Stereo Analyst Polygon Feature Attributes The polygon feature attributes define the attributes to be used for the specific polygon feature class The following inform
218. omated Tie Point Collection Bundle Block Adjustment Automated DTM Extraction Stereo Analyst To prevent misaligned orthophoto mosaics and to ensure accurate DTMs and 3D features tie points are commonly measured within the overlap areas of multiple images A tie point is a point whose ground coordinates are not known but is visually recognizable in the overlap area between multiple images Tie point collection is the process of identifying and measuring tie points across multiple overlapping images Tie points are used to join the images in a project so that they are positioned correctly relative to one another Traditionally tie points have been collected manually two images at a time With the advent of new sophisticated and automated techniques tie points are now collected automatically saving you time and money in the preparation of 3D GIS data Digital image matching techniques are used to automatically identify and measure tie points across multiple overlapping images Once GCPs and tie points have been collected the process of establishing an accurate relationship between the images in a project the camera sensor and the ground can be performed This process is referred to as bundle block adjustment Since it determines most of the necessary information that is required to create orthophotos DTMs DSMs and 3D features bundle block adjustment is an essential part of processing The components needed to perform a bund
219. ome expensive optical and mechanical components The resulting devices were analog digital hybrids Analytical aerotriangulation analytical plotters and orthophoto projectors were the main developments during this phase Outputs of analytical photogrammetry can be topographic maps but can also be digital products such as digital maps and DEMs Stereo Analyst Principles of Photogrammetry 32 Digital photogrammetry is photogrammetry applied to digital images that are stored and processed on a computer Digital images can be scanned from photographs or directly captured by digital cameras Many photogrammetric tasks can be highly automated in digital photogrammetry for example automatic DEM extraction and digital orthophoto generation Digital photogrammetry is sometimes called softcopy photogrammetry The output products are in digital form such as digital maps DEMs and digital orthophotos saved on computer storage media Therefore they can be easily stored managed and used by you With the development of digital photogrammetry photogrammetric techniques are more closely integrated into remote sensing and GIS Digital photogrammetric systems employ sophisticated software to automate the tasks associated with conventional photogrammetry thereby minimizing the extent of manual interaction required to perform photogrammetric operations One such application is LPS Project Manager the interface of which is shown in Figure 8 Figure 8
220. ommended that the original feature class files not be edited or modified Next The next section in this manual is a reference section In it you can find helpful information about installation and configuration feature collection ASCII files and STP files A glossary and list of references are also included for further study Stereo Analyst Next 220 Texturizing 3D Models Introduction Once you have collected your 3D GIS data you may want to add textures to your models making them as realistic as possible Attaching realistic textures to your 3D models is as simple as obtaining digital imagery of the building or landmark and mapping that imagery to the model using the Texel Mapper program supplied with Stereo Analyst This tour will lead you through the steps involved in accurately and realistically mapping images taken from ground level of the landmark with a digital camera onto the 3D model like the ones you collected in the previous tour a Getting Started First you must launch the Texel Mapper program From the Stereo Analyst menu select Texel Mapper x lene Arahal Click here Avie T ior bem Block to launch m MEMENNEEEEM Texel Mapper me edem Uk Hep The Texel Mapper opens Explore the Interface Take a few moments to explore the interface Stereo Analyst Getting Started 221 E Loading the Data Sets My Dese Rapper lO x m O00 DI WF xw 7 u Bm eK Loading the 3D Model Stereo A
221. on Racetrack race Racetrack 88 bmp 12007 Polygon Airport airport Airport 89 bmp 12008 Polygon Landing strip landing Landing Strip 90 bmp 12009 Polygon Well other than water windmill well b Well other 91 bmp 12010 Point Tanks tanks Tanks 92 bmp 12011 Point Covered reservoir reservoir Reservoir 93 bmp 12012 Polygon Gaging station gaging Gaging Sta 94 bmp 12013 Point Buildings and Related Features Continued Landmark object feature as labelled landmark Landmark 95 bmp 12014 Polygon Campground campground Campground 97 bmp 12015 Polygon Picnic area picnic Picnic Area 98 bmp 12016 Polygon Cemetery cemetery Cemetery 99 bmp 12017 Polygon Roads and Related Features Primary highway pri highway Primary 100 bmp 13000 Polyline Highway Secondary highway second hwy Second Hwy 101 bmp 13001 Polyline Light duty road light rd Light Duty Road 102 bmp 13002 Polyline Unimproved road unimpro rd Unimproved 103 bmp 13003 Polyline Road Trail trial sic Trail 104 bmp 13004 Polyline Dual highway dual hwy Dual Highway 105 bmp 13005 Polyline Dual highway with median strip dual hwy m Dual Hwy Strip 106 bmp 13006 Polyline Road under construction rd construct Road Construct 107 bmp 13007 Polyline Underpass overpass underpass Underpass 108 bmp 13008 Polyline Bridge bridge Bridge 109 bmp 13009 Polyline Drawbridge drawbridge Drawbridge 111 bmp 13010 Polyline Tunnel tunnel Tunnel 112 bmp 13011 Polyline Railroads and Related Features Sta
222. on of 3D and height information an adjacent set of photographs is used together with a stereoscope While in the field information and measurements collected on the ground are recorded directly onto the hardcopy photographs Using the hardcopy photographs information regarding the feature of interest is recorded both spatially geographic coordinates and nonspatially text attribution Transferring the geographic information associated with the hardcopy photograph to a GIS involves the following steps e Scan the photograph s e Georeference the photograph using known ground control points GCPs e Digitize the features recorded on the photograph s using the scanned photographs as a backdrop in a GIS e Merge and geolink the recorded tabular data with the collected features in a GIS Repeat this procedure for each photograph Example 2 Collecting Geographic Information from Hardcopy Photography Using a Transparency Rather than measure and mark on the photographs directly a transparency is placed on top of the photographs during feature collection In this case a stereoscope is placed over the photographs Then a transparency is placed over the photographs Features and information spatial and nonspatial are recorded directly on the transparency Once the information has been recorded it is transferred to a GIS The following steps are commonly used to transfer the information to a GIS e Either digitally scan the en
223. on of the Earth and its associated geography Various types of imagery can be used including aerial photography satellite imagery digital camera imagery videography and 35 mm photography With the advent of high resolution satellite imagery GIS data can be updated accurately and immediately Synthesizing the concepts associated with photogrammetry remote sensing GIS and 3D visualization introduces a new paradigm for the future of digital mapping one that integrates the respective technologies into a single comprehensive environment for the accurate preparation of imagery and the collection and extraction of 3D GIS data and geographic information This paradigm is referred to as 3D geographic imaging 3D geographic imaging techniques will be used for building the 3D GIS of the future Figure 3 3D Information for GIS Analysis Stereo Analyst Geographic Imaging 20 m From Imagery to a 3D GIS Stereo Analyst 3D geographic imaging is the process associated with transforming imagery into GIS data or more importantly information 3D geographic imaging prevents the inclusion of inaccurate or outdated information into a GIS Sophisticated and automated techniques are used to ensure that highly accurate 3D GIS data can be collected and maintained using imagery 3D geographic imaging techniques use a direct approach to collecting accurate 3D geographic information thereby eliminating the need to digitize from a secondary data
224. oods Woods 44 bmp 7000 Polygon Scrub scrub Scrub 45 bmp 7001 Polygon Orchard orchard Orchard 47 bmp 7002 Polygon Vineyard vineyard Vineyard 47 bmp 7003 Polygon Mangrove mangrove Mangrove 48 bmp 7004 Polygon Coastal Features Rock or coral reef coral Coral Reef 53 bmp 8000 Polygon Group of racks bare or awash exp rocks Exposed Rocks 54 bmp 8001 Polygon Stereo Analyst Default Stereo Analyst Feature Classes Table 9 Stereo Analyst Default Feature Classes Continued Feature Stereo Feature Feature Class File Analyst Bitmap FCODE Type Name fcl Name Breakwater pier jetty or wharf breakwater Breakwater 56 bmp 8002 Polyline Seawall seawall Seawall 58 bmp 8003 Polyline Bathymetric Features Area exposed at mean low tide area_expo Area Exposed 59 bmp 9000 Polyline Channel channel Channel 60 bmp 9001 Polyline Offshore oil or gas well platform offshore Offshore oil 61 bmp 9002 Point Sunken rock sunken_rock Sunken Rock 62 bmp 9003 Point Rivers Lakes and Canals Intermittent stream int_stream Int Stream 63 bmp 10000 Polyline Intermittent river int_river Inter River 64 bmp 10001 Polyline Perennial stream per_stream Per Stream 65 bmp 10002 Polyline Perennial river per_river Per River 66 bmp 10003 Polyline Small falls small rapids small_rapids Small Rapids 67 bmp 10004 Polyline Large falls large rap
225. opy cartographic and topographic maps and attributing the elevation of contour lines Subsequent interpolation of contour lines is required to create a DTM The digitization of these sources includes either scanning the entire map or digitizing individual features from the maps The accuracy and reliability of the topographic or cartographic map cannot be guaranteed As a result an error in the map is introduced into your GIS Additionally the magnitude of error is increased due to the questionable scanning or digitization process The second example involves merging existing DTMs with geographic information contained in a GIS Where did the DTMs come from How accurate are the DTMs If the original source of the DTM is unknown then the quality of the DTM is also unknown As a result any inaccuracies are translated into your GIS Can you easily edit and modify problem areas in the DTM Many times the problem areas in the DTM cannot be edited since the original imagery used to create the DTM is not available or the accompanying software is not available This example involves using ground surveying techniques such as ground GPS total stations levels and theodolites to capture angles distances slopes and height information You are then required to geolink and merge the land surveying information within the geographic information contained in the GIS Traditional Approaches 18 Problem Example 4 Problem Example 5
226. or the direct collection of 3D geographic information from a DSM using a 3D floating cursor Thus additional elevation data is not required True 3D information is collected directly from imagery During the collection of 3D GIS data a 3D floating cursor displays within the DSM while viewing the imagery in stereo The 3D floating cursor commonly floats above below or rests on the surface of the Earth or object of interest To ensure the accuracy of 3D GIS data the height of the floating cursor is adjusted so that it rests on the feature being collected When the 3D floating cursor rests on the ground or feature it can be accurately collected Workflow 25 Stereo Analyst Figure 4 Accurate 3D Buildings Extracted using Stereo Analyst Automated terrain following cursor capabilities can be used to automatically place the 3D floating cursor on the ground so that you do not have to manually adjust the height of the cursor every time a feature is collected For example the collection of a feature in 3D is as simple as using the automated terrain following cursor with stream mode digitizing activated In this scenario you simply hold the left mouse button and trace the cursor over the feature of interest The resulting output is 3D GIS data For the update and maintenance of a GIS existing vector layers are commonly superimposed on a DSM and then reshaped to their accurate real world positions 2D vector layers can be transformed into
227. ordinate system used by oriented stereopairs Ground coordinate space relates directly to the surface of the Earth Measurements in ground coordinate space are 3D including length width and elevation values Ground coordinate system A 3D coordinate system that utilizes a known map projection Ground coordinates X Y and Z are usually expressed in feet or meters Ground space Events and variables associated with the objects being photographed or imaged including the reference coordinate system Terms 281 Stereo Analyst Header file A portion of a sensor derived image file that contains ephemeris data The header file contains all necessary information to determine the exterior orientation of the sensor at the time of image acquisition Image coordinate space The coordinate system used by nonoriented stereopairs It is a 2D space where measurements are recorded in pixels Image scale SI Expresses the ratio between a distance in the image and the same distance on the ground Image space Events and variables associated with the camera or sensor as it acquired the images The area between perspective center and the image Inactive tool An inactive tool is a tool that is enabled but is not in use It appears unshaded denoting its enabled status in the Stereo Analyst feature toolbar but is not depressed which indicates an active tool See also Active tool Indian Remote Sensing Satellite IRS Satellites operated
228. orthorectified imagery is highly dependent on the accuracy of the DTM used to model the terrain effects caused by the surface of the Earth The DTM source is an additional source of input during orthorectification Acquiring a reliable DTM is another costly process High resolution DTMs can be purchased at a great expense Image Preparation for a GIS 17 B Traditional Approaches Example 1 Problem Example 2 Problem Example 3 Stereo Analyst Solution Stereo Analyst allows for the collection of 3D information you are no longer limited to only 2D information Using sophisticated sensor modeling techniques a DTM is not required as an input source for collecting accurate 3D geographic information As a result the accuracy of the geographic information collected in Stereo Analyst is higher There is no need to spend countless hours collecting DTMs and merging them with your GIS Unfortunately 3D geographic information cannot be directly measured or interpreted from geocorrected images orthorectified images raw photography or scanned topographic or cartographic maps The resulting geographic information collected from these sources is limited to 2D only which consists of X and Y georeferenced coordinates In order to collect the additional Z height information additional processing is required The following examples explain how 3D information is normally collected for a GIS The first example involves digitizing hardc
229. oscope F Buldegt Workspace click to select the Building 1 icon j 2 From the feature toolbar select the Orthogonal Snap tool L Once you select the Orthogonal Snap tool it remains depressed in the feature toolbar indicating that it is active 3 Move your mouse into the display area and position the cursor at one of the corners of the building 4 Adjust the cursor elevation by rolling the mouse wheel until it rests on top of the roof of the building 5 Click to collect that corner of the building then move the mouse and continue to digitize along the roof line adjusting the cursor elevation and x parallax as necessary Notice that with the second vertex the cursor is controlled so that you cannot digitize a line that is not 90 You can however add another vertex to the line you digitized to extend it 6 When you have completely digitized the roof of the building double click to close the polygon The filled polygon which corresponds to the roof of the building displays in the Main View Collect Building Features 196 This filled polygon has orthogonal corners Use the 3D Polygon Extend Tool 1 Stereo Analyst In the Main View position your cursor at a location on the ground close to the building In this case we suggest you use the corner of a nearby sidewalk Zoom in to see the detail of the sidewalk in the Left and Right Views Adjust the x parallax as necessary Using the Left and Ri
230. oss corners 5 Deselect the texturized faces of the model by right clicking outside of the model 6 Save the model by selecting File gt Save As gt Multigen OpenFlight Database and selecting texel_mapper_tour flt from the file list Overwrite the existing file with your latest changes Texturize the Other Side of the Model Repeat the above steps using the karolinenplatz left and the left side of the model This side is slightly more challenging as it contains fewer vertices and more perspective distortion B Editing the One of the shortcomings of using photographs of actual buildings to Texture texturize your model is that you also get artifacts in the pictures In other words you get a picture of the powerlines lamp posts and automobiles that happen to be parked in front of the building at the time the picture was taken The Texel Mapper provides an Image Edit utility to edit these artifacts out of the image and get a clean texture on the building Stereo Analyst Editing the Texture 230 Display a Texture with Texture Picking Options 1 2 Rotate the model to display the front of the model Enter the Texture Picking Options mode by clicking the Texture Picking Options button 7l on the Texel Mapper toolbar Right click on the front of the model The karlolinerplatx front texture displays in the workspace Image Edit Options Mode 1 Enter the Image Edit Options mode by clicking the Image Edit Option
231. ou select Yes the global feature class is permanently altered If you select No then the display properties and attributes changes are only saved to the feature class in the current project If you import a feature class with the same name but different attributes from a feature class already existing in the global feature class list in Stereo Analyst you are prompted as to whether or not you want to use the global feature class properties and attributes instead of the local feature class properties and attributes Choose Yes and discard attributes different from those stored in the global feature class list Choose No and the attributes in the feature class remain and a new class is added to the local feature project only Table 9 lists the default feature classes provided by Stereo Analyst Classes are divided by feature class categories which are indicated by shaded boxes Stereo Analyst Default Stereo Analyst Feature Classes Table 9 Stereo Analyst Default Feature Classes Feature Stereo Feature Feature Class File Analyst Bitmap FCODE Type Name fcl Name Horizontal Control With third order or better horiz contrl Horiz Control 1 bmp 1000 Point Checked spot elevation c_spt_elev Chkd Spot Elev 2 bmp 1001 Point Unmonumented unmonumented Unmonumented 3 bmp 1002 Point Vertical Control Third ord
232. oughout a DSM the software accounts and adjusts for y parallax automatically Using OpenGL software technology Stereo Analyst automatically accounts for the tilt and rotation of the two images as they existed when the images were captured Figure 33 DSM without Sensor Model Information Ph oy Wee oo amp uk Cg wer XK GH HB eer coo Scaling Translation and Rotation 68 E 3D Floating Cursor and Feature Collection Stereo Analyst Figure 34 DSM with Sensor Model Information Te Lamy es s ams He Deu WornoazemH BHBu emcutc ie rta LL oes aoe 57 BA MEE Cl ee oe ALA A DAA Figure 33 displays a digital stereo model created without sensor model information Figure 34 displays the use of epipolar resampling techniques for viewing a DSM created with sensor model information As a result of using automatic epipolar resampling display techniques 3D GIS data can be collected to a higher accuracy In order to accurately collect 3D GIS data from DSMs a 3D floating cursor must be adjusted so that it rests on the feature being collected For example if a road is being collected the elevation of the 3D floating cursor must be adjusted so that the floating cursor rests on the surface of the road In this case the elevation of the road and the 3D floating cursor would be the same A 3D floating cursor consists of a cursor displayed for the left image and an independent cursor displayed for the right image of a st
233. ping areas of two images based on the collinearity condition Space resection A technique used to determine the exterior orientation parameters associated with one image or many images based on the collinearity condition SPOT A series of Earth orbiting satellites operated by the Centre National d Etudes Spatiales CNES of France Stereo A stereo view is that in which there are two images that form a stereopair A stereopair can either be raw without coordinates or adjusted with coordinates Stereo Pair Chooser A dialog that enables you to choose stereopairs from a block file Stereo model Three dimensional image formed by the brain as a result of changes in depth perception and parallactic angles Two images displayed in a Digital Stereoscope Workspace for the purpose of viewing and collecting 3D information Stereopair A set of two remotely sensed images that overlap providing a 3D view of the terrain in the overlap area Stereo scene Achieved when two images of the same area are acquired on different days from different orbits one taken east of the vertical and the other taken west of the nadir Strip of photographs Consists of images captured along a flight line normally with an overlap of 60 for stereo coverage All photos in the strip are assumed to be taken at approximately the same flying height and with a constant distance between exposure stations Camera tilt relative to the vertical is assumed to be mi
234. ppropriate bmp file from the Feature Icon ist When you are finished the Create Custom Class dialog looks like the following Cneale Curio Clare Deme Dira Pepe Frater Ate bares Feature Chast s vim Fiere kel cales id You also have the option to assign an icon to the feature class Icons are bitmap bmp files D Cie icon bor Piratas laa 5 Click the Display Properties tab of the Create Custom Class dialog Since the feature class is Sidewalk the reasonable shape for drawing is a polyline 6 In the Select shape for drawing section click to select Polyline 7 If you wish click the dropdown list to select a different Line Color and enter a different Line Width The Display Properties tab looks like the following Stereo Analyst Create a New Feature Project 176 Stereo Analyst Creale Custom Chase The Display Properties tab NT Decio Procesos Feature hsbunes is where you define what the feature class looks like Pori in the Digital Stereoscope Workspace Polyline is the appropriate choice for a sidewalk Select a Line Color and Line Width Some Attributes are assigned by default depending on the type of shape you select Click OK to add the Custom Feature Class to the Category you specified The Attributes are automatically selected depending on the type of shape for drawing you select for your custom feature If you wish you can add additional attributes he
235. principal point for each image in the project Therefore the image positions of the fiducial marks are measured on the image and then compared to the calibrated coordinates of each fiducial mark Since the image space coordinate system has not yet been defined for each image the measured image coordinates of the fiducial marks are referenced to a pixel or file coordinate system The pixel coordinate system has an x coordinate column and a y coordinate row The origin of the pixel coordinate system is the upper left corner of the image having a row and column value of 0 and O respectively Figure 18 illustrates the difference between the pixel coordinate system and the image space coordinate system Figure 18 Pixel Coordinate System vs Image Space Coordinate System Ya file Yo file Xo file Fiducial mark Using a 2D affine transformation the relationship between the pixel coordinate system and the image space coordinate system is defined The following 2D affine transformation equations can be used to determine the coefficients required to transform pixel coordinate measurements to the corresponding image coordinate values x a a X azY y b b X b Y Stereo Analyst Interior Orientation 45 Lens Distortion Stereo Analyst The x and y image coordinates associated with the calibrated fiducial marks and the X and Y pixel coordinates of the measured fiducial marks are used to determine six affine transfor
236. r accuracies Similarly rarely are there enough accurate GCPs for a project of thirty or more images to perform space resection that is a minimum of 90 is required In the case that there are enough GCPs the time required to identify and measure all of the points would be costly The costs associated with block triangulation and orthorectification are largely dependent on the number of GCPs used To minimize the costs of a mapping project fewer GCPs are collected and used To ensure that high accuracies are attained an approach known as bundle block adjustment is used A bundle block adjustment is best defined by examining the individual words in the term A bundled solution is computed including the exterior orientation parameters of each image in a block and the X Y and Z coordinates of tie points and adjusted GCPs A block of images contained in a project is simultaneously processed in one solution A statistical technique known as least squares adjustment is used to estimate the bundled solution for the entire block while also minimizing and distributing error Block triangulation is the process of defining the mathematical relationship between the images contained within a block the camera or sensor model and the ground Once the relationship has been defined accurate imagery and geographic information concerning the surface of the Earth can be created and collected in 3D When processing frame camera digital camera videog
237. r portion of the Stereo Analyst window Buckets can contain the 3D Measure tool the Position tool and any Attribute Table you want to display Buckets are populated in the order in which you select tools to work with in Stereo Analyst Bundle block adjustment A mathematical technique that determines the position and orientation of each image as they existed at the time of image capture determines the ground coordinates measured on overlap areas of multiple images and minimizes the error associated with the imagery image measurements and GCPs Terms 277 Stereo Analyst Cache A temporary storage area for data that is currently in use The cache enables fast manipulation of the data When data is no longer held by the cache it is returned to the permanent storage place for the data such as the hard drive CAD see Computer aided design Calibration certificate report In aerial photography the manufacturer of the camera specifies the interior orientation in the form of a certificate or report CCD See Charge coupled device Charge coupled device CCD A semiconductor technology used to build light sensitive electronic devices such as cameras and image scanners FOLDOC 2000a Collinearity A nonlinear mathematical model that photogrammetric triangulation is based upon Collinearity equations describe the relationship among image coordinates ground coordinates and orientation parameters Collinearity condition
238. r the point measurements 5 Use the scroll bar to see the first Angle measurement Angle Pt 1 Pt 2 Pt 3 180 8987 degrees Stereo Analyst Take 3D Measurements 158 Reading Angle Measurements NOTE The angles measured are always counterclockwise To understand the meaning of this measurement consult the following diagram Pt 1 angle x Pt 3 m Pt2 The measurement displays in the 3D Measure tool as follows Angle Pt 1 Pt 2 Pt 3 180 8592 degrees where Pt 1 Pt 2 Pt 3 is the list The line is translated as follows At Pt 2 the central point in the list the angle from Pt 1 to Pt 3 left to right in the list is 180 8592 degrees The angle is reported in decimal degrees and is graphically represented as follows Pt1 Approximately 180 degrees Pt 2 PES View the Digitized Line Stereo Analyst You can zoom out and see the line you just digitized in the Main View You can see double lines due to x parallax and the change in elevation as you digitized the sidewalk Click and hold the wheel while moving the mouse toward you to zoom out Zoom out until the entire sidewalk you have just digitized displays in the Main View Using the left mouse button adjust the image in the Main View until the entire sidewalk is visible Take 3D Measurements 159 Notice the large x parallax in this area Take the Second Now that you know how to digitize a polyline move to a different Meas
239. raphy and nonmetric camera imagery block triangulation is commonly referred to as aerial triangulation AT When processing imagery collected with a pushbroom sensor block triangulation is commonly referred to as triangulation Digital Mapping Solutions 53 There are several models for block triangulation The common models used in photogrammetry are block triangulation with the strip method the independent model method and the bundle method Among them the bundle block adjustment is the most rigorous of the above methods considering the minimization and distribution of errors Bundle block adjustment uses the collinearity condition as the basis for formulating the relationship between image space and ground space In order to understand the concepts associated with bundle block adjustment an example comprising ten images with multiple GCPs whose X Y and Z coordinates are known is used Additionally six tie points are available Figure 23 illustrates the photogrammetric configuration Figure 23 Photogrammetric Block Configuration Fl kgms Elk Leica Phologerammetry Suile Project Manager Phe Ede hees Heb Du dO I G A z fimi 7 Bic Largas bik Y eges El batted img Bf xiii gl PEER zog ches a tethelaa11g i a tethelaa sd i e ethelaa ed i 9 pres D dmi a D drip a ELESE Stereo Analyst B00 287 lre Mane Digital Mapping Solutions 54 Stereo Analyst Forming the Collinear
240. re T For information on creating additional attributes see the On Line Help 9 Click OK in the Create Custom Class dialog Create a New Feature Project 177 The following Attention dialog opens kilimin lads Ha Click No to preserve the original Stereo Analyst feature classes i Dia pour eani do aem Hause clair Sadessalk r o goial nada Yet Dant Ask The Again 10 Click No in the Attention dialog By clicking No the Sidewalk feature class is included as part of the current project only and the feature classes originally distributed with Stereo Analyst remain unaltered It is highly recommended that the original feature class files not be edited or modified You are returned to the Feature Classes tab The Sidewalk feature class has been added to the Roads and Related Features category 11 Click the checkbox to select the Sidewalk feature class Select Rivers Lakes and Canals 1 Click the Category dropdown list and select Rivers Lakes And Canals 2 Click the checkbox next to the Per River feature class Select Vegetation 1 Click the Category dropdown list and select Vegetation 2 Click the checkbox next to Woods The Feature Classes tab now looks like the following with all the feature classes listed along the right hand side under Selected Classes Stereo Analyst Create a New Feature Project 178 LE Projeti Geva Festa Cita Stare Mitel Silo clase ho incllade
241. re Use the increment nudgers to change the layer display If you find it easier to work with monochrome images you can use this dialog to make changes 2 Usethe increment nudgers to change the layers assigned to Red and Green to 3 3 Click Apply The image redisplays in monochrome Ca Es 4 Change Red layer back to 1 and the Green layer back to 2 then click Apply The image displays with its default layer to color assignments 5 Click the Close button on the Band Combinations dialog Stereo Analyst Adjust Display Resolution 85 Change Brightness and Contrast 1 2 You can type values here or 3 4 5 H Add a Second Image Stereo Analyst Right click to access the Quick Menu again Move your mouse over Left Image then select Brightness Contrast The Contrast Tool dialog opens Loesiras fool lor la DN br adjust the brightness and contrast with the slider bars Adjust the brightness and contrast meters by clicking holding and moving the sliding bars right or left then click Apply Depending on the settings you choose the image may appear better or worse to you in the Main View Return the image to its default display by clicking Reset then click Apply Click Close in the Contrast Tool dialog Add a Second Image 86 Stereo Analyst WV For the remainder of the tour guide you need either red blue anaglyph glasses or stereo glasses that work in conjun
242. re listed here Dau Eo ir GATO meam car Poe ran Licor150808 See TRS E EL A ADMI a ade La This block file has projection information Left and right images display in the monoscopic views If you wish to view only the overlapping area of the two photographs comprising a DSM you can set an option to that effect From the Utility menu select Stereo Analyst Options Then click the Stereo View Options option category Click to select the Mask Out Non Stereo Regions option a Open the Stereo You can select various DSMs from the western accuracy blk file Pair Chooser To do so you open the Stereo Pair Chooser dialog With it you can select a DSM that suits criteria you specify such as overlap area 1 In the Digital Stereoscope Workspace click the Stereo Pair Chooser icon The Stereo Pair Chooser dialog opens Stereo Analyst Open the Stereo Pair Chooser 132 The images in the block file are geographically represented here The possible imagel combinations are listed here F Dum Filed a E Bakani mad E Diada ot EHC l The Stereo Pair Chooser is equipped with a CellArray You can use the CellArray to select different image pairs from the block file These image pairs can then be displayed in the stereo view The overlap areas of the image footprints displayed in the Stereo Pair Chooser can also be interactively selected to choose a DSM of interest Once a DSM has been graphically selected the cor
243. re modes in Stereo Analyst is the feature collection mode In this mode you are actually collecting features from a DSM displayed in the Digital Stereoscope Workspace As you collect features you are adding attribution data to the attribute tables associated with each feature class See also Feature editing mode Feature editing mode One of the two feature modes in Stereo Analyst is the feature editing mode In this mode you use tools to edit features you have already collected from a DSM As you edit features their attribute information is updated in the attribute tables See also Feature collection mode Feature extraction The process of studying and locating areas and objects on the ground and deriving useful information from images Feature ID FID Each feature in a feature project has its own ID number which enables you to identify and select it individually Terms 280 Stereo Analyst Feature Project A Feature Project contains all the feature classes and their corresponding attribute tables you need to create features in your stereo views FID See Feature ID Fiducial center The center of an aerial photo Fiducial marks Four or eight reference markers fixed on the frame of an aerial metric camera and visible in each exposure Fiducials are used to compute the transformation from data file to image coordinates Floating mark Two individual cursors one for the right image of the stereopair and one for the left i
244. re the Interface oooo common 221 Loading the Data Sets 222 Texturizing the Model eene 223 Texturize a Face In Affine Map Mode 223 Texturize a Perspective Distorted Face 226 Editing the Texture ooo 230 Tiling a Texture rrr 233 Adding the Texture to the Tile Library 233 Tiling Multiple Faces o oooooooo ee 233 Scaling the Tiles aunar tac e a a EC 234 Add a new Image to the Library 235 Autotiling the Rooftop o ooo 236 Reference Material nnn nn 239 Feature Projects and Classes 241 Stereo Analyst Introduction es 241 Stereo Analyst Feature Project and Project File 241 Stereo Analyst Feature Classes 244 General Information ooo oo ooo 244 Table of Contents vii Point Feature ClaSS 0 0 o ooo llle 245 Polyline Feature Class o o o oo oo es 246 Polygon Feature ClaSS o o ooooooo como mo 247 Default Stereo Analyst Feature Classes 248 Using Stereo Analyst ASCII Files 255 Introduction een 255 ASCII Categories c r 255 Introductory Text lees 255 Number of Classes lees 255 Shape Class Number leere 255 Shape Class 2 5 x E nae dede Er e daro 258 Shape Class
245. red to create a DSM see Workflow 3 Click OK in the Select Layer To Open dialog NOTE If you have not already created pyramid layers for the images in the block file you are prompted to do so The first DSM associated with the western accuracy blk file displays in the Digital Stereoscope Workspace once the block file opens Stereo Analyst Open a Block File 149 eis block file and the current stereopair are listed here f my Tesi Eh Cate Ras nee amp 9n Coe Tose 1 9 ks L ma M TAE A iuh aie If you wish to view only the overlap area associated with a DSM you can set an option to achieve that effect From the Utility menu select Stereo Analyst Options Then click the Stereo View Options option category Click to select the Mask Out Non Stereo Regions option a Open the Stereo You can select various DSMs from the western accuracy blk file Pair Chooser To do so you open the Stereo Pair Chooser With it you can select stereopairs that suit criteria you specify such as overlap area 1 In the Digital Stereoscope Workspace click the Stereo Pair Chooser icon The Stereo Pair Chooser opens Stereo Analyst Open the Stereo Pair Chooser 150 The stereopair you select is outlined in the graphic area of the Stereo Pair Chooser The possible image combinations and their overlap percentages are listed here in the CellArray Click Apply to display the new stereopair in the Digital Ste
246. reoscope Workspace Stereo Analyst Sioro Pals rn G sd E Dose Filed D Sham clectoimages Prism N OM epot e 3s Shoes peip sen The Stereo Pair Chooser is equipped with a CellArray You can use the CellArray to select different DSMs from the block file These DSMs can then be displayed in the Digital Stereoscope Workspace Click to select row 2 in the 1D column This is the image pair consisting of 252 img and 253 img Notice that the highlighted row corresponds to the highlighted portion of the footprint in the Stereo Pair Chooser You can see the overlap area that is going to be displayed in the Digital Stereoscope Workspace In this case you can see that the overlap area is approximately 44 The overlap areas of the image footprints displayed in the Stereo Pair Chooser can also be interactively selected to choose a DSM of interest Once a DSM has been graphically selected the corresponding DSM displays in the CellArray Click Apply in the Stereo Chooser The new DSM displays in the Digital Stereoscope Workspace 4 Click Close in the Stereo Chooser Open the Stereo Pair Chooser 151 H Take 3D Measurements Open the 3D Measure Tool and the Position Tool Now that you have the DSM displayed you can use some of the other Stereo Analyst tools to take measurements of buildings roads and other features in the DSM In this portion of the tour guide you are going to work with the 3D Measure tool to measure fe
247. required for creating triangulated irregular networks TINs and import and export in 3D e Create DSMs from external photogrammetric sources e Open block files for the automatic creation and display of DSMs e Directly output and immediately use your ESRI 3D Shapefiles in ERDAS IMAGINE and ESRI Arc products Stereo Analyst is designed for you with the following objectives in mind e Provide an easy to use airphoto image interpretation tool for the collection of qualitative and quantitative geographic information from imagery e Provide a fast and optimized 3D stereo viewing environment e Bridge the technological gap between digital photogrammetry and GIS e Provide an intuitive tool for the collection of height information Stereo Analyst Introduction 3 H About Stereo Analyst Stereo Analyst Menu Bar Stereo Analyst e Provide a tool for the collection of geographic information required as input for a GIS Before you begin working with Stereo Analyst it may be helpful to go over some of the menu options and icons located on the interface You use these throughout the tour guides that follow Stereo Analyst is dynamic That is menu options buttons and icons you see displayed in the Digital Stereoscope Workspace change depending on the tasks you can potentially perform there This is accomplished through the use of dynamically loaded libraries DLLs Dynamically Loaded Libraries A DLL is used when you s
248. responding images are highlighted in the CellArray 2 Click to select row 2 in the ID column This is the DSM consisting of images 252 img and 253 img When you have selected that row the Stereo Pair Chooser looks like the following Stereo Analyst Open the Stereo Pair Chooser 133 Sloreo Pals Chosaor w x3 The stereopair you select is outlined in the graphic area of the Stereo Pair Chooser Es The amount of overlap is indicated here Set overlap tolerance here E hugo Filed Shan veleta imager lector O Color F epot 40 ax B Shows ceda ann xe Ims e Notice that the highlighted row corresponds to the appropriate DSM footprint in the Stereo Pair Chooser You can see the overlap area that is going to be displayed in the Digital Stereoscope Workspace In this case the area contains approximately 44 overlap 3 Click Apply in the Stereo Pair Chooser dialog Again you may be prompted to calculate pyramid layers this time for the image 253 img 4 If necessary click OK in the Attention dialog to compute pyramid layers for 253 img The DSM updates in the Stereo Analyst Digital Stereoscope Workspace 5 Click Close in the Stereo Pair Chooser dialog Stereo Analyst Open the Stereo Pair Chooser 134 a Open the Position Tool Stereo Analyst The selected DSM displays in the Digital Stereoscope Workspace Now that you have the appropriate DSM displayed you can use some of the other Ster
249. rrect the difference in the X Y and Z direction between the original position and the displayed position can be visually interpreted and recorded The Position tool can also be used to collect 3D point positions for use in other applications The resulting 3D point positions can be used for geocorrection orthorectification or highly accurate point determination Specifically the steps you are going to execute in this example include e Select a block file e Open the Stereo Pair Chooser e Select a DSM e Open the Position tool e Enter the 3D coordinates of the check points into the Position tool e Observe the check point positions in 3D stereo e Record the difference between the original 3D check point position and the displayed check point position Stereo Analyst Introduction 129 Getting Started H Open a Block File Stereo Analyst The data used in this tour guide covers the campus of The University of Western Ontario in London Ontario Canada The four photographs were captured at a photographic scale of 1 6000 The photographs were scanned at a resolution of 25 microns The resulting ground coverage is 0 15 meters per pixel Seven check points are used to check the accuracy of the DSM The seven check points were calculated using conventional surveying techniques to an accuracy of approximately 0 05 meters in the X Y and Z directions Approximate completion time for this tour guide is 30 minute
250. rrespond to the same feature on the right image Adjusting x parallax allows you to adjust the left and right image positions so that they correspond to the same feature This approach is also used while measuring GCPs to be used for orthorectification If the image positions of a feature on the left and right image do not correspond the measurement is inaccurate Using Stereo Analyst the two cursors are adjusted simultaneously so that they fuse into one floating cursor that rests on the ground To rest the floating cursor on the ground x parallax for a given feature must be adjusted Since the x parallax contained within a 3D DSM varies with elevation you need to adjust x parallax throughout a DSM during 3D point positioning measurement and feature collection A tool known as the automated terrain following cursor automates and simulates the process associated with placing the floating cursor on the ground Cursor Height Adjustment 105 The following illustration shows the effect of adjusting x parallax for the placement of the floating cursor on the ground Flight Principal Point Source Moffit and Mikhail Adjusting the floating cursor changes the appearance of the left and right image The floating cursor is adjusted so that it rests on the feature Once the floating cursor rests on the feature the left and right image positions are located on the same feature Floating Above a Feature The following fig
251. rtices A polyline or polygon is composed of multiple vertices These vertices like a single vertex have X Y and Z components You can adjust the X and Y component of vertices of a polyline or polygon by using feature editing tools such as Reshape You can also add a vertex or vertices to an existing feature To edit the Z component use the C key on the keyboard See also Vertex Terms 288 Stereo Analyst Workspace A Digital Stereoscope Workspace is where you complete digital mapping tasks The Digital Stereoscope Workspace allows you to view stereo imagery and collect 3D features from stereo imagery X parallax The difference in position of a common ground point appearing on two overlapping images which is a function of elevation X parallax is measured horizontally X parallax is required to measure elevation and cannot be completely removed from a stereopair Y parallax The difference in position of a common ground point appearing on two overlapping images which is caused by differences in camera position and rotation between two images Y parallax is measured vertically Z The vertical height component of a vertex floating cursor or feature Terms 289 Stereo Analyst Terms 290 Index Symbols blk Block file 275 dbf Database file 241 fcl Feature class file 241 fpj Feature project file 241 275 prj Projection file 241 rrd Pyramid layer file 102 shp Shapefile 241 shx
252. s You must have both Stereo Analyst and the example files installed to complete this tour guide NOTE This tour guide was created in color anaglyph mode If you want your results to match those in this tour guide set your stereo mode to color anaglyph by selecting Utility gt Stereo Analyst Options Stereo Mode Stereo Mode Color Anaglyph Stereo First you must launch Stereo Analyst For instructions on launching Stereo Analyst see Getting Started Once Stereo Analyst has been started and you have an empty Digital Stereoscope Workspace you are ready to begin The first step in checking the accuracy of the DSM involves opening a block file The block file contains all of the necessary information required to automatically create and display a DSM in real time The block file in this example was created in LPS Project Manager Camera calibration and GCP information was input and used to calculate all of the necessary sensor model information The resulting accurate sensor model information is used to calculate and display 3D coordinate information For the remainder of the tour guide you need either red blue glasses or stereo glasses that work in conjunction with an emitter Open a Block File 130 Select the Workspace and Add the blk File 1 From the toolbar of the empty Digital Stereoscope Workspace click the Open icon x The Select Layer To Open dialog opens Here you select the type of file
253. s a clear cover placed over two images which form a stereopair Then features are hand drawn on the transparency and can then be transferred to digital format by scanning or digitizing A brand of transparency is Mylar Triangulated Irregular Network TIN A TIN enables you to collect TIN points and create breaklines in an image displayed in a stereo view A TIN is a type of DEM that unlike a raster grid based model allows you to place points at varying intervals Triangulation Establishes the geometry of the camera or sensor relative to objects on the surface of the Earth Two dimensional See 2D United States Geological Survey USGS An organization dealing with biology geology mapping and water For more information visit the web site www usgs gov USGS See United States Geological Survey Vertex A vertex is a component of a feature digitized in the Digital Stereoscope Workspace A vertex is made up of three axes X Y and Z The Z component corresponds to the elevation of the vertex A feature can be composed of only one vertex that is a point as ina TIN or many vertices that is a polyline or polygon You can adjust the X Y and Z components of an existing vertex See also Point Polyline and Polygon Vertical exaggeration The effect perceived when a DSM is created and viewed Vertical exaggeration is also referred to as relief exaggeration and is the evidence of height differences in a stereo model Ve
254. s along the perimeter of the parking lot 9 Double click to close the perimeter of the parking lot 10 Hold the Shift key and click to select the boundary of the forest feature then of the parking lot feature The boundary sharing is evident in the following illustration This is the shared boundary notice the absence of vertices in this area PE orm d 11 Click outside the feature to deselect it 12 Click the Zoom to Full Extent icon a n uj E Check Attributes Now that you have collected a number of features you can check the attribute tables Alternatively you can open attribute tables for specific features as you digitize This enables you to input information into attribute fields you specify For example the Building 1 feature class might have an attribute field for an address 1 Click the Attribute icon il next to the Building 1 feature class Stereo Analyst Check Attributes 216 The Digital Stereoscope Workspace adjusts to accommodate the Building 1 Attributes ih Ew T Re FORRES amp e r COL SO 123 L Dr tidan Lame k isin pea EIA rum Lar Like the Stereo Analyst tools attribute tables occupy the bottom portion of the interface 2 Left click the 1 column under ID Click here to Buking 1 Abu select the row Cake FDede FID Ace Perret Ai Z __ pam E BE ml pan 3 zum CO This attribute corresponds to the first building you collected You
255. s button E on the Texel Mapper toolbar The model is hidden and the active image displays with a yellow box the Source Box and a red box the Destination Box The portion of the image enclosed by the Source Box is used to replace the portion of the image in the Destination Box Source box Destination box Remove an Automobile Artifact Stereo Analyst There are two cars parked in front of the building We will attempt to remove one of these artifacts from the image To move the Destination Box drag each of the vertices so that they cover the blue compact car in the image Keep the vertices in their same relative positions That is make sure that the upper left vertex remains in the upper left position after you move the box If you reverse any of these vertices the image in the Destination Box will be appear and be applied inverted or as a mirror image of the Source Box Editing the Texture 231 Stereo Analyst The entire car is covered by the Destination Box PI L Try to keep the Box as square as possible Drag the vertices of the Source box so that they enclose an unobstructed portion of the hedge that is roughly the same size as the compact car Use the left mouse button to pan through the image and the center mouse button to zoom in on the portion of the image that you are editing Fine tune your Source and Destination Boxes so that The Source Box as a result the image is slightly smaller
256. s superior to paper both in terms of image detail and geometry These units usually have a Root Mean Square Error RMSE positional accuracy of 4 microns or less and are capable of scanning at a maximum resolution of 5 to 10 microns 5 microns is equivalent to approximately 5 000 pixels per inch The required pixel resolution varies depending on the application Aerial triangulation and feature collection applications often scan in the 10 to 15 micron range Orthophoto applications often use 15 to 30 micron pixels Color film is less sharp than panchromatic therefore color ortho applications often use 20 to 40 micron pixels The optimum scanning resolution also depends on the desired photogrammetric output accuracy Scanning at higher resolutions provides data with higher accuracy Desktop scanners are general purpose devices They lack the image detail and geometric accuracy of photogrammetric quality units but they are much less expensive When using a desktop scanner you should make sure that the active area is at least 9 x 9 inches which enables you to capture the entire photo frame Desktop scanners are appropriate for less rigorous uses such as digital photogrammetry in support of GIS or remote sensing applications Calibrating these units improves geometric accuracy but the results are still inferior to photogrammetric units The image correlation techniques that are necessary for automatic tie point collection and elevation e
257. s the DSM from which you collect features Click OK to load the DSM into the Digital Stereoscope Workspace 5 In the Current Images for Feature Collection section of the Stereo Model tab click to select 252 img amp 253 img NOTE If you have not already created pyramid layers for all images in the block file you are prompted to do so 6 If necessary click OK in the dialog to calculate pyramid layers for the image 253 img 7 Click OK in the Feature Project dialog to transfer all the information to the Digital Stereoscope Workspace Stereo Analyst Create a New Feature Project 180 Stereo Analyst 8 The DSM is adjusted in the Digital Stereoscope Workspace You can see that the classes you chose are all neatly arranged in the Feature Class Palette on the left side of the Digital Stereoscope Workspace You still have access to the same views the Main View the OverView and the Left and Right Views Adjust the size of the Feature Class Palette and the views to your liking F For the remainder of the tour guide you need either red blue glasses or stereo glasses that work in conjunction with an emitter Create a New Feature Project 181 Notice that some of the feature collection tools are enabled they have not been enabled up to this tour guide since you have not yet collected or edited features Stereo Analyst The name of the block file and DSM in the Digital Stereoscope Workspac
258. scope Workspace 76 Load the LA Data e erlrrrns 77 Open the Left Image nnns 78 Adjust Display Resolution 80 LOOM ii Soest se se tae SA C a a a A 80 ROdlTl secede E ee ee ai ee Oe ed OS AA we BP 82 Check Quick Menu Options 0 o o ooo ooo oo 83 Add a Second Image eser 86 Adjust and Rotate the Display 88 Examine the Images o ooooooooo rr 88 Orient the Images l 000 eee ee 89 Rotate the Images ceres 91 Adjust X parallax leere 94 Adjust Y parallaX llle 96 Position the 3D Cursor 97 Practice Using Tools 100 Zoom Into and Out of the Image 100 Save the Stereo Model to an Image File 101 Open the New DSM cess 102 Adjusting X Parallax s 103 Adjusting Y Parallax ee 104 Cursor Height Adjustment 105 Floating Above a Feature o o oo ooooo oo 106 Floating Cursor Below a Feature lr 107 Cursor Resting On a Feature o oo 108 Next 1 20 exam SUE See du Et ad ee Re 109 Creating a DSM from External Sources 111 Introduction 29 102 vee tee Rex 111 Stereo Analyst Table of Contents v Checking the Accuracy Getting Started s 113 Load the LA Data c n 114 Open the Left Imag
259. sion The perception of depth through binocular vision is referred to as stereoscopic viewing With stereoscopic viewing depth information can be perceived with great detail and accuracy Stereo viewing allows the human brain to judge and perceive changes in depth and volume In photogrammetry stereoscopic depth perception plays a vital role in creating and viewing 3D representations of the surface of the Earth As a result geographic information can be collected to a greater accuracy as compared to traditional monoscopic techniques Stereo feature collection techniques provide greater GIS data collection and update accuracy for the following reasons e Sensor model information derived from block triangulation eliminates errors associated with the uncertainty of sensor model position and orientation Accurate image position and orientation information is required for the highly accurate determination of 3D information e Systematic errors associated with raw photography and imagery are considered and minimized during the block triangulation process e The collection of 3D coordinate information using stereo viewing techniques is not dependent and reliant on a DEM as an input source Changes and variations in depth perception can be perceived and automatically transformed using sensor model information and raw imagery Therefore DTMs containing error are not introduced into the collected GIS data Digital photogrammetric techniques used
260. sition Tool Geometric Properties Stereo Analyst Options View Show Hide the cursor tracking tools Stereo Pair Chooser Invert Stereo Update from Fallback Fit Scene To Window Reset Zoom and Rotation Set Scene To Default Zoom Set Scene To Specified Zoom Feature Feature Project Properties Undo Feature Edit Cut Copy Paste Show XYZ Vertices Show All Features Hide All Features Show 3D Feature View 2D Snap 3D Snap Boundary Snap Right Angle Mode Parallel Line Mode Stream Digitizing Mode Polygon Close Mode Reshape Extend Polyline Remove Line Segment Add Element Select Element 3D Extend Import Features Export Features Raster Undo Raster Edit Left Image gt Right Image gt Help Help Navigation Help Installed Component Information Installed Graphics And Driver Information About Stereo Analyst Stereo Analyst About Stereo Analyst 5 Stereo Analyst Toolbar The Stereo Analyst toolbar like the menu bar has dynamic icons that are active or inactive depending on your configuration and what displays in the Workspace Table 2 Stereo Analyst Toolbar El Information New Click this icon to open a new blank Digital 3 Stereoscope Workspace Open Click this icon to open an IMAGINE Image i img block file bIk or Stereopair stp file in the
261. solution Stereo Analyst utilizes all of the information processed in LPS Project Manager and accounts for inaccuracies during 3D feature collection measurement and interpretation Orthorectification Stereo Analyst Geocorrected aerial photography and satellite imagery have large geometric distortion that is caused by various systematic and nonsystematic factors Photogrammetric techniques used in LPS Project Manager eliminate these errors most efficiently and create the most reliable and accurate imagery from the raw imagery LPS Project Manager is unique in terms of considering the image forming geometry by utilizing information between overlapping images and explicitly dealing with the third dimension which is elevation Orthorectified images or orthoimages serve as the ideal information building blocks for collecting 2D geographic information required for a GIS They can be used as reference image backdrops to maintain or update an existing GIS Using digitizing tools in a GIS features can be collected and subsequently attributed to reflect their spatial and nonspatial characteristics Multiple orthoimages can be mosaicked to form seamless orthoimage base maps Problems Orthorectified images are limited to containing only 2D geometric information Thus geographic information collected from orthorectified images is georeferenced to a 2D system Collecting 3D information directly from orthoimagery is impossible The accuracy of
262. southeastern corner of the forest in more detail 2 Adjust the parallax as necessary to get a clear view of the parking lot Stereo Analyst Collect a Forest Feature 214 Stereo Analyst Share boundaries here Vertex 1 Vertex 2 entry for boundary sharing Vertex 3 exit of boundary sharing 3 From the Feature menu select Boundary Snap A check mark appears next to the Boundary Snap option Veatare Piece Propias Jes reper ber Paste Show Xr Vedan Esse All Featured Made dl amas Boundary Snap is accessed Snap from the Feature menu E TH bide bate ERG Tt Click to select the Parking Lot feature cl EH IC O selec e rKI eature class m Using the previous picture as a guide click to select the first vertex of the Parking Lot feature at Vertex 1 This vertex is not included in the shared boundary Again using the picture as a guide click to place a vertex Vertex 2 on an existing vertex of the forest feature This is the entry point for boundary sharing At this time Stereo Analyst is recording information about the boundary to be shared Collect a Forest Feature 215 7 Click to place Vertex 3 on the farthest common vertex of the forest feature This is the exit point of boundary sharing At this point you may notice that the digitizing line temporarily disappears This means that the Boundary Snap tool is sharing the boundaries of the two features 8 Continue to collect vertice
263. ssociated with the polyline you just digitized Polyline 2 Polyline 2 Length 162 5347 meters Once again this is the total length of the line segments comprising the polyline Notice the second line of data Z difference 7 2846 meters Z mean 246 6845 meters Continue to scroll down to view the rest of the results in the 3D Measure tool text field Take 3D Measurements 161 View the Digitized Line You can zoom out and see the line you just digitized in the Main View You can see double lines due to the change in x parallax and elevation along the street edge 1 Click and hold the wheel while moving the mouse toward you to zoom out 2 Zoom out until the entire road you have just digitized displays in the Main View 3 Using the left mouse button adjust the image in the Main View until the entire road is visible Since you made adjustments as you collected points the parallax improves where you finished digitizing Take the Third Next you are going to measure an ice rink using the Polygon tool Measurement Enter the 3D Coordinates 1 Click the Zoom 1 1 icon 2 2 In the Position tool double click in the X field and type 477677 91 3 In the Y field type 4761070 12 4 In the Z field type 242 98 Digitize the Polygon Stereo Analyst drives to the 3D coordinate position you specify Stereo Analyst Take 3D Measurements 162 Digitize this feature 1 If required adjust the x parallax to get
264. st The 3D mass points can then be interpolated to create a TIN or a raster DEM DTMs form the basis of many GIS applications including watershed analysis line of sight LOS analysis road and highway design and geological bedform discrimination DTMs are also vital for the creation of orthorectified images LPS Automatic Terrain Extraction ATE can automatically extract DTMs from imagery Orthorectification is the process of removing geometric errors inherent within photography and imagery Using sensor model information and a DTM errors associated with sensor orientation topographic relief displacement Earth curvature and other systematic errors are removed to create accurate imagery for use in a GIS Measurements and geographic information collected from an orthorectified image represent the corresponding measurements as if they were taken on the surface of the Earth Orthorectified images serve as the image backdrops for displaying and editing vector layers 3D GIS data and information can be collected from what is referred to as a DSM Based on sensor model information two overlapping images comprising a DSM can be aligned leveled and scaled to produce a 3D stereo effect when viewed with appropriate stereo viewing hardware A DSM allows for the interpretation collection and visualization of 3D geographic information from imagery The DSM is used as the primary data source for the collection of 3D GIS data 3D GIS allows f
265. stimate or adjust the values associated with exterior orientation e Estimate the X Y and Z coordinates associated with tie points e Estimate or adjust the values associated with interior orientation e Minimize and distribute data error through the network of observations Data error is attributed to the inaccuracy associated with the input GCP coordinates measured tie point and GCP image positions camera information and systematic errors The least squares approach requires iterative processing until a solution is attained A solution is obtained when the residuals or errors associated with the input data are minimized Digital Mapping Solutions 56 Stereo Analyst The least squares approach involves determining the corrections to the unknown parameters based on the criteria of minimizing input measurement residuals The residuals are derived from the difference between the measured and computed value for any particular measurement in a project In the block triangulation process a functional model can be formed based upon the collinearity equations The functional model refers to the specification of an equation that can be used to relate measurements to parameters In the context of photogrammetry measurements include the image locations of GCPs and GCP coordinates while the exterior orientations of all the images are important parameters estimated by the block triangulation process The residuals which are minimize
266. stortion along a radial distance r from the principal point Wolf 1983 In most camera calibration reports the lens distortion value is provided as a function of radial distance from the principal point or field angle LPS Project Manager accommodates radial lens distortion parameters in both radial and tangential lens distortion Three coefficients kg k and kz are computed using statistical techniques Once the coefficients are computed each measurement taken on an image is corrected for radial lens distortion Exterior orientation defines the position and angular orientation of the camera that captured an image The variables defining the position and orientation of an image are referred to as the elements of exterior orientation The elements of exterior orientation define the characteristics associated with an image at the time of exposure or capture The positional elements of exterior orientation include Xo Yo and Zo They define the position of the perspective center O with respect to the ground space coordinate system X Y and Z Zo is commonly referred to as the height of the camera above sea level which is commonly defined by a datum The angular or rotational elements of exterior orientation describe the relationship between the ground space coordinate system X Y and Z and the image space coordinate system x y and z Three rotation angles are commonly used to define angular orientation They are Omega o Ph
267. supports the use of TIF JPEG Generic Binary Raw Binary and other commonly used image formats Using DLLs the various image formats no longer need to be imported for use within Stereo Analyst Simply select the image format of choice from the Files of type dropdown list and use the imagery in Stereo Analyst for the creation of DSMs Navigate to the directory where you saved the files then select the file named la left img Click OK in the Select Layer To Open dialog As Stereo Analyst opens the file pyramid layers are optionally generated Pyramid layers allow the image to display faster in the Main View at whatever resolution you choose Pyramid layers are layers of the image data that are successively reduced by a power of two x Mites ird ue ph eis ter ped cm A Fur gery rath peed din Cause den ide peramanee decerdi n the oe d the rage Would pou lioe te compute complete broma pyre URAMI rici CE vu 5 Click OK in the dialog prompting you to create pyramid layers Stereo Analyst Open the Left Image 79 The file of Los Angeles la left img displays in the Digital Stereoscope Workspace NOTE The screen captures provided in this tour guide were generated in the Color Anaglyph Stereo mode If you are running Stereo Analyst with Quad Buffered Stereo configuration your images appear in natural color These tools The name of the image displays in the title bar of the workspace are E Mr B t Wow
268. t Once two mono images are displayed in the Digital Stereoscope Workspace Stereo Analyst uses the Stereo Mode display you specify in the Options dialog which in the case of this tour guide is Color Anaglyph Stereo Add a Second Image 87 H Adjust and Rotate the Display Examine the Images Stereo Analyst This is the left image of the stereopair This is the right image of the stereopair In order to view stereo images in the Main View your eye base the distance between your left eye and your right eye must be parallel to the photographic base of the two photographs The photographic base is the distance between the left image camera exposure station and the right image camera exposure station If your eye base is not parallel to your photographic base you are not able to perceive the DSM in 3D The two images currently displayed in the Main View are not parallel to your eye base For this reason the images must first be rotated so that they are parallel to your eye base You may be asking yourself How do I know if the images are properly oriented for stereo viewing The following steps can be used to determine the proper orientation of any two photographs for stereo viewing NOTE For the purposes of this section simple illustrations are used to represent the left and right images of the stereopair Left image Right image e Stadium PP dii Expressway 1 Visually identify the ce
269. t and elevation information Under certain conditions and circumstances viewing a DSM may be difficult The following factors influence the quality of stereo viewing e Unequal flying height between adjacent photographic exposures This effect causes a difference in scale between the left and right images As a result the 3D stereo view becomes distorted e Flight line misalignment during photographic collection This results in large differences in photographic orientation between two overlapping images As a result you experience eyestrain and discomfort while viewing the DSM e Erroneous sensor model information Inaccurate sensor model information creates large differences in parallax between two images comprising a DSM As a result of these factors the DSMs contain an effect referred to as y parallax To you y parallax introduces discomfort during stereo viewing Figure 31 displays a stereo model with a considerable amount of y parallax Figure 32 displays a stereo model with no y parallax Stereo Models and Parallax 66 m Scaling Translation and Rotation Stereo Analyst Figure 31 Y parallax Exists To minimize y parallax you are required to scale translate and rotate the images until a clear and comfortable stereo view is available Scaling the stereo model involves adjusting the perceived scale of each image comprising a stereopair This can be achieved by adjusting the scale that is relative hei
270. t the feature is within the crosshair using the Enable Update option in the Position tool Record the new X and Y coordinate positions then subtract the old values from the new values to determine accuracy If necessary adjust the height of the cursor Record the new Z coordinate then subtract the old value from the new value to determine accuracy Check that Enable Update button is not active and the Zoom is set to approximately 1 0 In the Position tool type the following X Y and Z values respectively 477344 68 4761657 79 and 269 99 Use the Position Tool 140 3 Position the cursor and visually interpret the location of the 3D floating cursor over the feature Compute X Y Coordinate and Z Elevation Accuracy 1 If necessary adjust the image so that the feature is within the crosshair using the Enable Update option in the Position tool 2 Record the new X and Y coordinate positions then subtract the old values from the new values to determine accuracy 3 If necessary adjust the height of the cursor 4 Record the new Z coordinate then subtract the old value from the new value to determine accuracy Fourth Check Point 1 Check that Enable Update button is not active and the Zoom is set to approximately 1 0 2 In the Position tool type the following X Y and Z values respectively 477327 95 4760990 42 and 257 79 Stereo Analyst Use the Position Tool 141 3 Position the cursor
271. t various parts of the image since elevation varies throughout the area imaged on the photographs As elevation changes so does parallax Therefore you must compensate for the variations in parallax to ensure that a clear and optimum 3D display is provided A clear and optimum 3D stereo display is provided when y parallax has been removed and the amount of x parallax is sufficient for conveying elevation changes within a local geographic area of interest If the sensor model information associated with the two images is available Stereo Analyst automatically rotates scales and adjusts the images while viewing the DSM DSMs created using sensor model information are also referred to as oriented DSMs Real world geographic coordinates can be collected from oriented DSMs From the toolbar of the empty Digital Stereoscope Workspace click the Open icon The Select Layer To Open dialog opens Here you select the type of file you want to open in the Digital Stereoscope Workspace Open the Left Image 78 Select Layer To gen Fe pensi Hule Lack in En Choose the image la_left img E Ia nghi mg Flerame ade en Choose IMAGINE Image Fiet ci tese BASHE braga mel from the dropdown list Irueb los S700 Feet x 3700 Coles x T Bae Click the Files of type dropdown list and select IMAGINE Image img Other image types can also be used for the creation of DSMs Stereo Analyst directly
272. tart a new application such as a Feature Project or import export utility Until you request an option the system resources required to run it need not be used Instead they can be put to use in increasing processing speed The menu bar across the top of the Stereo Analyst Digital Stereoscope Workspace has different options depending on what you have displayed in the Workspace If you have a feature project displayed the options are different than if you have a DSM displayed For example the Feature menu feature collection tools and feature editing tools are not enabled unless you are currently working on a feature project Similarly the tools available to you at any given time depend on what you currently have displayed in the Workspace For example if you are working with a single stereopair and not an block file you cannot use the Stereo Pair Chooser The full complement of menu items follows mm B For additional information about each of the Stereo Analyst tools see the On Line Help About Stereo Analyst 4 Table 1 Stereo Analyst Digital Stereoscope Workspace Menus File New gt Open gt Save Top Layer Export gt View to Image Close All Layers Exit Workspace Utility Terrain Following Cursor Fixed Cursor Maintain Constant Cursor Z Left Only Mode Right Only Mode Rotation Mode Block Image Path Editor Create Stereo Model Tool 3D Measure Tool Po
273. tate the Display 92 Stereo Analyst NOTE Notice the position of the stadium with the clockwise rotation 5 Move the mouse ann additional 180 degrees clockwise 6 When you are finished click once to remove the axis then click the Rotate Tool icon Gl again to deselect it Once the photographs have been properly oriented a clear 3D stereo view displays Adjusting the images along the x direction modifies the vertical exaggeration of the 3D DSM Consult the simple illustration again to see that with the rotation of the images the principal points are now separated along the x direction Adjust and Rotate the Display 93 Before rotation gt Principal points of each After rotation y Principal points of image are separated each image are now along the y direction separated along the a x direction Adjust X parallax Stereo Analyst To adjust the depth or vertical exaggeration of the images you must adjust the amount of x parallax Adjusting the x parallax of the images provides a clear and optimum 3D DSM for viewing and interpreting information If the area of interest experiences too much vertical exaggeration interpreting geographic information becomes increasingly difficult and inaccurate If the area of interest experiences minimal vertical exaggeration slight variations in elevation cannot be interpreted In Stereo Analyst you can reduce the amount of x parallax
274. tely 3 acres or 3 553 square feet 1 acre has 43 560 square feet The length around its perimeter is approximately 149 meters 2 Notice the second line of data Z difference 0 0662 meters Z mean 240 8134 meters This means that there was approximately a 0662 meter difference between the highest point on the ice rink that you measured and the lowest 3 Continue to scroll down to view the rest of the results in the 3D Measure tool text field You get results for each of the points you digitized to create the ice rink Take the Fourth Next you are going to digitize a field using the Polygon tool Measurement Enter the 3D Coordinates 1 Click the Zoom to Full Resolution icon El E 2 2 Inthe Position tool click in the X field and type 477018 51 3 In the Y field type 4761296 26 4 In the Z field type 253 36 Digitize the Polygon Stereo Analyst drives to the 3D coordinate position you specify This wide field has a unique shape 1 Position the cursor within the crosshair and use the wheel to zoom in until the field is visible in the Main View Collect data about this open field 2 Adjust the x parallax and cursor elevation as necessary to obtain an optimum 3D stereo view Stereo Analyst Take 3D Measurements 164 Click the Polygon tool in the 3D Measure tool Position your cursor at one corner of the field and click to digitize the first vertex Continue to digitize around the perimeter of the fi
275. tes that the image is being viewed at its original resolution that is one image pixel equals one screen pixel An image scale value greater than 1 indicates that the image is being viewed at a magnification factor larger than the original resolution For example an image scale of 2 indicates that the image is being displayed at 2 times the original image resolution An image scale less than 1 indicates that the image is being viewed at a resolution less than the original image resolution For example an image scale of 0 5 indicates that the image is being displayed at half of the original image resolution Scale displays here in Since you are only viewing one image the status area the Left and Right Views are empty Roam Now that you have sufficiently zoomed into the image so that you can see geographic details you can roam about the image to see other areas Stereo Analyst Adjust Display Resolution 82 The status area also displays the row and column image pixel coordinates of the cursor When an oriented DSM displays the 3D X Y and Z coordinates of the cursor are displayed When two images comprising a nonoriented DSM are displayed the corresponding pixel coordinates of the cursor for the left and right images are displayed 1 Inthe Main View click and hold down the left mouse button and move the mouse forward and backward left and right to see other portions of the image Hold down the left button gt
276. tinued Click this icon to open the 3D Feature View This view allows you to see features that you have digitized in three dimensions You can change the color of the model the background color in the 3D Feature View as well as add textures from the original imagery to the model You can also export the model so that it can be used in other applications Invert Stereo Click this icon to reverse the display of the Left and Right images This makes tall features appear shallow shallow features appear tall You may have to click this icon to correct the way a stereopair displays in the Digital Stereoscope Workspace Update Scene Click this icon to update the scene with the full resolution This button is only active when the Use Fallback Mode option in the Performance category is set to Until Update For more information see the On Line Help Fixed Cursor Mode Click this icon to enable the fixed cursor mode When you are in fixed cursor mode you can use the mouse to move the image in the Main View however the cursor does not change position in X Y or Z Create Stereo Model Click this icon to open the Create Stereo Model dialog With it you can create a block file from external sources You simply need two independent images and camera information available from the data vendor to create the block file 3D Measure Tool Click this tool to take measurements in a stereopair The 3D Measure
277. tion Interchange ASCII A basis of character sets to convey some control codes space numbers most basic punctuation and unaccented letters a z and A Z FOLDOC 1999 Anaglyph An anaglyph is a 3D image composed of two oriented or nonoriented stereopairs To view an anaglyph you require a pair of red blue glasses These glasses isolate your vision into two distinct parts corresponding with the left and right images of the stereopair This produces a 3D effect with vertical information Analog photogrammetry Optical or mechanical instruments such as analog plotters used to reconstruct 3D geometry from two overlapping photographs Analytical photogrammetry The computer replaces some expensive optical and mechanical components by substituting analog measurement and calculation with mathematical computation Terms 276 Stereo Analyst Anti aliasing In a DSM anti aliasing appears as shimmering effects visible in urban areas due to limited texture mapping ASCII See American Standard Code for Information Interchange AT See Aerial triangulation Attribute An attribute is a piece of information stored by Stereo Analyst about a feature you have collected in the Digital Stereoscope Workspace For example if you collect a road feature attributes associated with that feature include the X Y and Z components of each vertex making up the road Attribute information also includes the total line length You can add additional
278. tion of each image as it existed when it was captured The orientation is determined relative to an X Y and Z coordinate system The rotation order defines which angle is modeled first second and third with respect to the X Y and Z coordinate axis In North America the order of Omega Phi and Kappa is most commonly used e Photo direction the photo direction defines whether the images are aerial or ground based that is terrestrial images If aerial images are used the photo direction is the Z axis If ground based images are used the photo direction is the Y axis Stereo Analyst Introduction 111 e Two overlapping images these images represent the same geographic area on the surface of the Earth or object being modeled e Camera calibration this is information such as focal length and principal point offset in the x and y direction This information is commonly provided in a calibration report e The six interior orientation coefficients for each image these six coefficients are also referred to as affine transformation coefficients They represent the relationship between the file and or pixel coordinate systems of the image and the film or image space coordinate system The values summarize the scale and rotation differences between the two coordinate systems e The six exterior orientation parameters for each image the six exterior orientation parameters define the position X Y Z and orientation Omega Phi
279. tire transparency using a desktop scanner or digitize only the collected features using a digitizing tablet e The resulting image or set of digitized features is then georeferenced to the surface of the Earth The information is georeferenced to an existing vector coverage rectified map rectified image or is georeferenced using GCPs Once the features have been georeferenced geographic coordinates X and Y are associated with each feature Stereo Analyst Image Preparation for a GIS 14 e Ina GIS the recorded tabular data attribution is entered and merged with the digital set of georeferenced features This procedure is repeated for each transparency Example 3 Collecting Geographic Information from Scanned Photography Geoprocessing Techniques Stereo Analyst By scanning the raw photography a digital record of the area of interest becomes available and can be used to collect GIS information The following steps are commonly used to collect GIS information from scanned photography e Georeference the photograph using known GCPs e Ina GIS using the scanned photographs as a backdrop digitize the features recorded on the photograph s e Inthe GIS merge and geolink the recorded tabular data with the collected features This procedure is repeated for each photograph Raw aerial photography and satellite imagery contain large geometric distortion caused by camera or sensor orientation error terrain relief Earth
280. tool to create a 3D Building feature Open the Position Tool 1 Click the Position tool icon in the toolbar of the Digital Stereoscope Workspace The Digital Stereoscope Workspace adjusts to accommodate the Position tool 2 In the Position tool type the value 477966 in the X field then press Enter on your keyboard 3 Type 4761623 in the Y field then press Enter 4 Type 264 32 in the Z field then press Enter 5 Type 3 0 in the Zoom field then press Enter The tower displays in the Digital Stereoscope Workspace 6 Zoom in so that the tower fills the Main View Stereo Analyst Collect Building Features 189 7 8 Adjust the x parallax as necessary NOTE When you collect very tall features such as this tower that are surrounded by shorter features x parallax is necessarily adjusted for only the feature of interest that is the roof The stereo view of surrounding features and the ground is poor This tower is so tall that there is a large amount of parallax Click the Close icon X in the Position tool to maximize the display area Select the Building Feature and Digitize 1 Stereo Analyst From the Feature Class palette click to select the Building 1 icon F Buldegt Move your mouse into the display area and position the cursor at one of the corners of the tower Adjust the cursor elevation by rolling the mouse wheel until it rests on top of the roof of the tower Click to collect that
281. ture View You can view the features you digitize in another view the 3D Feature View Like the other views it has options that can change the display of features In the 3D Feature View however you can manipulate the feature so that you can see all of its sides top and bottom You can also export features from the 3D Feature View to formats such as wrl VRML for use in other applications like IMAGINE VirtualGIS 1 Zoom in so that the tower fills the Main View 2 Click the 3D Feature View icon El A 3 Click on one of the line segments of the tower to select it The tower is highlighted and displays in the 3D Feature View Stereo Analyst Collect Building Features 193 Fa May Se Miras bus Mb e ES Be eos D wsap a Tob FLERE LE Foy a ag 2 Mig 1 di 3 1 i D Lair Din Pad Display features in SD using the SD Feature View Right click in the 3D Feature View to access the 3D View Options menu i T ies Ophore Click the Use Textures option Bachaground Calor Moda Coser Export Mica Click to select the Use Textures option The feature redisplays in the 3D Feature view with the textures which are real life attributes of the feature Stereo Analyst Collect Building Features 194 8 Collect the Third Building Textures reveal windows on th tower Practice manipulating the feature in the view by clicking and holding the left or middle mouse buttons and then moving the mouse in th
282. type coordinates of the point in the road where you will begin digitizing 2 In the Position tool type the value 477756 in the X field then press Enter on your keyboard 3 Type 4761342 in the Y field then press Enter 4 Type 243 98 in the Z field then press Enter 5 Type 0 8 in the Zoom field then press Enter The point where you begin digitizing displays in the Main View Now enter coordinates into the Position tool so you can see where you will finish digitizing the road 6 In the Position tool type the value 477968 in the X field then press Enter on your keyboard 7 Type 4761411 in the Y field then press Enter 8 Type 238 85 in the Z field then press Enter Stereo Analyst Collect Roads and Related Features 201 The point where you end digitizing displays in the Main View The following picture illustrates both the beginning and ending points Digitize from this pol in the road to this point in the road 9 Click the Close icon X in the Position tool to maximize the display area 10 Adjust the stereopair in the Main View so that the starting point displays Select the Road Feature and Digitize 1 From Feature Class Palette click to select the Light Duty Road icon F Ud Dal Fred 2 From the feature toolbar select the Parallel Line tool s Once you select the Parallel Line tool it remains depressed in the feature toolbar 3 Move your mouse into the display area and position the c
283. ue Rubber sheeting A 2D rectification technique to correct nonlinear distortions which involves the application of a nonlinear rectification 2nd order or higher Scene In Stereo Analyst a scene is made up of the stereo view and the data layers including any features that are displayed in the stereo view A scene can be in either mono or stereo The four major features of a scene are the stereo view a menu bar a toolbar and a status message bar Screen digitizing The process of drawing vector graphics on the display screen with a mouse Self calibration A technique used in bundle block adjustment to determine internal sensor model information Sensor A device that gathers energy converts it to a digital value and presents it in a form suitable for obtaining information about the environment Shapefile A shapefile is an ESRI vector format that contains spatial data This data is recorded in Stereo Analyst in the form of attributes in an attribute table These attributes include X and Y coordinates Multiple shapefiles can be saved in one Stereo Analyst Feature Project See also Vector SI See Image scale Terms 286 Stereo Analyst Single frame orthorectification Orthorectification of one image at a time using the space resection technique A minimum of 3 GCPs is required for each image Space intersection A technique used to determine the ground coordinates X Y and Z of points that appear in the overlap
284. ulated for each image of a stereopair The original left and right image coordinates and positions are transformed according to their degree of orientation which is defined as Omega Phi and Kappa and position The epipolar resampling process minimizes the differences between the left and right image orientation and position As a result y parallax is removed The remaining parallax is x parallax The variation in x parallax throughout the DSM is proportional to the variation of elevation Coplanarity Condition The epipolar resampling procedure uses the concepts associated with the coplanarity condition The coplanarity condition states that the two sensor exposure stations of a stereopair any ground point and the corresponding image positions on the two images must all lie in a common plane Stereo Analyst Epipolar Resampling 263 H STP File Characteristics Stereo Analyst Figure 42 Epipolar Geometry and the Coplanarity Condition Epipolar plane Li L2 Exposure gt Exposure station 1 station 2 Epipolar line y X Zp Yo Xp Source Keating Wolf and Scarpace 1975 The common plane is also referred to as the epipolar plane The epipolar plane intersects the left and right images and the lines of intersection are referred to as epipolar lines The image positions of a ground point appearing on the left and right photos lie along the epipolar line The epipolar resampling process transforms the orig
285. ure illustrates the floating cursor above a feature Notice that in the Left and Right Views the cursor position on the left and right images is located over different features Stereo Analyst Cursor Height Adjustment 106 Figure 39 Cursor Floating Above a Feature nah ime mi Du xw EFD 45gmBHB 8m amp s vr Goce UD 1646 LE 550g Floating Cursor Below a The following figure illustrates the floating cursor below a feature Feature Once again notice that the cursor position on the left and right image is located over different features Stereo Analyst Cursor Height Adjustment 107 Figure 40 Cursor Floating Below a Feature nk ime mi Da w ED x BIBBHM B 4A Coc SOs 16046 LS r 5000 Far GT rr n LL dk Hp Scam i Cursor Resting On a The following figure illustrates the floating cursor resting on the Feature feature of interest The left and right cursor positions are located on the same feature Stereo Analyst Cursor Height Adjustment 108 Figure 41 Cursor Resting On a Feature Fis Uy e isa re Cee Bred Xx 06AS5S 6 4 4 coe o 1644 Ls r s5mnmm Next In the next tour guide you can learn how to create a DSM using external sources To do so you enter calibration interior and exterior information which Stereo Analyst uses to create an block file A DSM made using this technique is considered oriented that is it contains projection information Stereo Analyst Next 109 Stereo
286. urement area of the stereopair and collect another Enter the 3D Coordinates 1 Click the Zoom 1 1 icon gl 2 In the Position tool click in the X field and type 477696 18 3 In the Y field type 4761404 26 4 In the Z field type 248 38 Digitize the Polyline Stereo Analyst drives to the 3D coordinate position you specify The road as illustrated in the figure below like the sidewalk you just digitized has a good deal of slope to it as you move southward Start digitizing here 1 Click in the 3D Measure tool and select the Polyline tool 2 Position your 3D floating cursor at the top of the bend in the road indicated with a circle in the previous illustration Stereo Analyst Take 3D Measurements 160 Stereo Analyst 3 Adjust the 3D floating cursor elevation and parallax as required so that it rests on the road Digitize southward along the road NOTE Remember to correct x parallax and cursor elevation as you digitize Digitize to the next bend in the road indicated with a circle in the following illustration NOTE The coordinates of this point are approximately 477829 04 4761339 82 and 241 37 6 Once you have finished digitizing the road double click to terminate the polyline Evaluate Results The measurements are reported in the text field of the 3D Measure tool NOTE Your results will likely differ from those presented here Use the scroll bar to see the first line of data a
287. ursor at the location where the sidewalk meets the road on the left side 4 Adjust the cursor elevation by rolling the mouse wheel until it rests on the ground NOTE You may find this easier if you zoom into the image 5 Click to digitize the first vertex on the left side of the road 6 Move your mouse across the road and click to digitize the first vertex on the right side of the road Stereo Analyst Collect Roads and Related Features 202 7 Move your mouse back to the left side of the road and click to collect the next vertex 8 Adjust the cursor elevation as necessary this road has a good deal of slope and continue to collect the road to the sidewalk as depicted in the previous illustration 9 Double click to stop digitizing the road The following picture illustrates the termination of the road zoomed in You can extend this road feature Zoom Out to See the Entire Feature 1 Use your mouse to zoom out so that the entire portion of the road you just digitized is visible in the Main View f gt In this illustration you can see many of the features you digitized 2 Zoom in to and out of the image to see the parallel lines Note that you need to adjust x parallax in order to see the digitized points and the road clearly at different elevations Stereo Analyst Collect Roads and Related Features 203 Extend the Road Feature When you zoom out to see the area you just digitized you may decid
288. vatives with respect to the unknown parameters the matrix transposed the matrix containing the weights of the observations L the matrix containing the observations Once a least squares iteration of processing is completed the corrections to the unknown parameters are added to the initial estimates For example if initial approximations to exterior orientation are provided from airborne GPS and INS information the estimated corrections computed from the least squares adjustment are added to the initial value to compute the updated exterior orientation values This iterative process of least squares adjustment continues until the corrections to the unknown parameters are less than a threshold commonly referred to as a convergence value The V residual matrix is computed at the end of each iteration of processing Once an iteration is completed the new estimates for the unknown parameters are used to recompute the input observations such as the image coordinate values The difference between the initial measurements and the new estimates is obtained to provide the residuals Residuals provide preliminary indications of the accuracy of a solution The residual values indicate the degree to which a particular observation input fits with the functional model For example the image residuals have the capability of reflecting GCP collection in the field After each successive iteration of processing the residuals become smaller until they
289. vesting in unsuitable geographic areas Prior to beginning expensive exploration projects geologists take an inventory of a geographic area using imagery as the primary source of information DSMs are frequently used to improve the quantity and quality of geologic information that can be interpreted from imagery Changes in topographic relief are often used in lithological mapping applications since these changes together with the geomorphologic characteristics of the terrain are controlled by the underlying geology DSMs are utilized for lithologic discrimination and geologic structure identification Dip angles can be recorded directly on a DSM in order to assist in identifying underlying geologic structures By digitizing and collecting geologic information using a DSM the resulting geologic map is in a form and projection that can be immediately used in a GIS Together with multispectral information high resolution imagery produces a wealth of highly accurate 3D information for the geologist Local Government Stereo Analyst In order to formulate social economic and cultural policies GIS sources must be timely accurate and cost effective High resolution imagery provides the primary data source for obtaining up to date geographic information for local government applications Existing GIS vector layers are commonly superimposed onto DSMs for immediate update and maintenance DSMs created from high resolution imagery are used for
290. way Adjust the elevation of the cursor by rolling the mouse wheel until the cursors converge If you do not have a mouse equipped with a wheel you can hold the C key on the keyboard as you simultaneously hold the left mouse button Then move the mouse forward and away from or backwards and toward you to adjust elevation Move the mouse in this direction Hold dow is the left button P Notice how the cursor appears to float above at and below ground level as you adjust it using the mouse Practice moving the mouse in this way until you can tell the cursor is on the ground NOTE Remember that you can also check the 3D cursor position by using the Left and Right Views If the cursor appears to be positioned on the same point in the views then it is positioned on the feature as in the illustration below Position the 3D Cursor 98 In the example that follows the cursor is positioned on the top overpass of the expressway You can experiment with this area by placing the cursor on the various levels that make up the expressway The cursor is located at the intersection 9 Move to another area of the stereopair such as the stadium and practice adjusting the cursor elevation Stereo Analyst Position the 3D Cursor 99 Practice Using Tools Zoom Into and Out of the Image Stereo Analyst Stereo Analyst can maintain the cursor at a specific Z elevation if you wish This is control
291. xtraction are often sensitive to scan quality Therefore errors attributable to scanning errors can be introduced into GIS data that is photogrammetrically derived One of the primary factors contributing to the overall accuracy of 3D feature collection is the resolution of the imagery being used Image resolution is commonly determined by the scanning resolution if film photography is being used or by the pixel resolution of the sensor In order to optimize the attainable accuracy of GIS data collection the scanning resolution must be considered The appropriate scanning resolution is determined by balancing the accuracy requirements versus the size of the mapping project and the time required to process the project Table 4 lists the scanning resolutions associated with various scales of photography and image file size Scanning Aerial Photography 38 Table 4 Scanning Resolutions 12 microns 16 microns 25 microns 50 microns 85 microns 2117 dpi 1588 dpi 1016 dpi 508 dpi 300 dpi Photo Scale coverage Coverage Coverage Coverage Coverage meters meters meters meters meters 1800 0 0216 0 0288 0 045 0 09 0 153 2400 0 0288 0 0384 0 06 0 12 0 204 3000 0 036 0 048 0 075 0 15 0 255 3600 0 0432 0 0576 0 09 0 18 0 306 4200 0 0504 0 0672 0 105 0 21 0 357 4800 0 0576 0 0768 0 12 0 24 0 408 5400 0 0648 0 0864 0 135 0 27 0 459 60
292. you want to open in the Digital Stereoscope Workspace 2 Click the Files of type dropdown list and select IMAGINE OrthoBASE Block File Select Lager To pen E Select the file CN western_accuracy blk Select block file from the dropdown list F e namwe meten ati hk Fiet of ypa PAAISIHE Dios SE ick Fin bi Fieras pees Feci Ae e EU pleni fei tri es eue Blk Spi 3 Navigate to the IMAGINE HOME vexamplesWWestern directory then select the file named western accuracy blk 4 Click OK in the Select Layer To Open dialog A dialog opens that prompts you to create pyramid layers for the files in the block file western accuracy blk Once you create pyramid layers for the files you are not prompted to do so again Aliens 3 7 m usa i n Click OK to generate blo tr Ere is mime rmi pyramid layers yiii can cause diwr ido poa depor an he ion ed be re Would you Pe le computo c rsplele barea eed lagers ness 5 Click OK to compute pyramid layers After the pyramid layers are generated the block file of The University of Western Ontario displays in the Digital Stereoscope Workspace If the block file contains more than one DSM Stereo Analyst automatically displays the first DSM in the block file Options described later in this tour guide can be used to select other DSMs contained within the block file Stereo Analyst Open a Block File 131 The name of the block file and the current stereopair a
293. yst Digitizing Options 5 When you have completely digitized the roof of the building double click to close the polygon The filled polygon which corresponds to the roof of the building displays in the Main View The filled polygon shows that it is not selected Selected polygons display all of their vertices Use the 3D Polygon Extend Tool One of the helpful tools provided by Stereo Analyst is the 3D Polygon Extend tool With it you can extend polygons such as the roof you just digitized to meet the ground This produces a 3D feature You can use the 3D Polygon Extend tool on polylines and polygons 1 In the Main View position your cursor at a location on the ground close to the building In this case we suggest you use the corner of a grassy area close to the first corner you digitized as depicted in the following illustration Stereo Analyst Collect Building Features 186 Position the cursor on the ground in this grassy area near the foundation of the building 2 Adjust the x parallax as necessary 3 Using the Left and Right Views as a guide adjust the height of the cursor with the mouse wheel until the cursor rests on the ground The cursor is at the same location in both the left and the right image Now that you have positioned the cursor on the ground you can create a 3D polygon 4 Click on a line segment of the polygon you created NOTE You can tell the feature is selected bec

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Stereo Analyst ® User's Guide