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AZGCORR - Airborne Research & Survey Facility

1. Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 55 20051015 Azimuth Systems User Guide AZGCORR Image items are either direct instrument recorded data or values derived from these Allowance is made for values overflowed underflowed or missing The following strategy has been adopted and must be followed in level 2 processing to remain compatible with level 3 programs a UINT16 image items have two special values Oxffff 65536 indicates an overflowed value zero indicates underflowed or missing data b FLOAT32 image items have two similar special values to allow for flexibility for level 2 processing these values are stored in ATM and CAS Vgroup items SCimover and SCimunder The following rule must be adhered to to avoid image data loss valid image items must be between SCimover and SCimunder images values gt SCimover and lt SCimunder will be omitted from level 3 calculations Note that these items are valid for UINT16 and FLOAT32 image data Default values are UINT16 SCimover 65536 0 SCimunder 0 0 Default values are FLOAT32 SCimover 1 0e 30 SCimunder 1 0e 30 3 Tiled images Image tiling is indicated by SCtiles gt 0 Image is tiled into side by side squares by no of pixels Image data for tiles are stored in the image data items ATdata CAimage spatial mode CAsrc Note that CAimage spectral mode and CAils are not tiled and always stored in one piece The key to the position o
2. yinc per line Using this vector the coordinates any any pixel pix line zero relative is given by x y posimag 2 pix posimag 4 line posimag 6 posimag 3 pix posimag 5 line posimag 7 6 CASI CCD pixel view angle table This table is used for lens error correction for scanners that use a lens to form an image of a slit to be projected on the diffraction grating If required the table file should have been supplied along with the scanner data 7 Image position adjustment From azgcorr v4 5 0 user controls are provided to adjust for view vector instrument pointing errors these are described in section 5 12 above and detailed in section under u parameters The ATM2 and CASI vdata item SCposcorr saves the latest version of these parameters that have been applied to the image linked to the vgroup The SCposcorr vector contains Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 56 20051015 Azimuth Systems entry 0 1 2 3 4 5 6 7 8 9 10 Remote Sensing Scanner Processing System Version 3 00 units secs degs deg User Guide contents time correction nav to scans attitude corrections for pitch roll and heading aircraft height adjustment x y WGS84 corrections applied using uow z WGS84 height correction using uow xX y z grid corrections applied using uo AZGCORR c Azimuth Systems 1996 2005 57 20051015
3. 132 132 F64 F32 F32 F32 F32 F32 F32 132 F32 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 F32 F32 C8 F32 C8 C8 F32 F32 132 132 F32 F32 132 132 F32 F32 132 132 132 132 132 132 132 132 CA maxv OoOw HhHHKRHROD AN oooos o 4 N e r a a a ea ee var var var var 32 32 32 var var var var var var var var var var var var i ee Cee Cee Cee ee User Guide AZGCORR description Vgroup description CASI scanner details and data Vgroup 1st processing program Vgroup 2nd processing program Vgroup 3rd processing program Vgroup 4th processing program CASI scanner serial number CASI scanner software version number Exabyte tape external label name Field tape file number Scanner configuration file name Target start day of year Target start time HHMMSS CASI operating mode flag 0 spatial 1 spectral 2 full frame G coefficients CCD integration period msecs CASI file header reported aperture Aperture appearing in majority of none dark frame headers Pixel of CCD optical axis Total field of view dec degs partial fov from port side to nadir pixels visible in fov pixel view angle table from port see general note 6 CCD port side flag Site start scan Site end scan Number of looks in spectral image Look spacing in spectral image Centre look pixel in spectral image Number of channels per band summed in enhanced spectr
4. ATprog3 C8 40 Vgroup 3rd processing program ATprog4 C8 40 Vgroup 4th processing program ATsbend 132 1 Sbend correction applied in scanner flag O no 1 yes Note 1 ATrgyro 132 1 Roll gyro correction applied in scanner flag O no 1 yes Note 1 AThddt C8 16 HDDT tape external label name Note 1 AtTcct C8 64 CCT tape external label name Note 1 ATtype C8 8 Daedalus ATM type eg 1268 ATid C8 32 ATM ID ATfov F32 1 Field of view dec degs ATpixfov F32 1 Pixel field of view ATpixrec 132 1 Pixels per scan recorded ATpixred 132 1 Pixels per scan reduction method 0 none 1 average 2 nearest ATpixsav 132 1 Pixels per scan saved ATsscan 132 1 Target start scan ATescan 132 1 Target end scan ATchan 132 1 Channels bands recorded ATbpix 132 1 Bits per pixels recorded ATgains F32 var Channel gains ATwavu F32 var Channel upper wavelength limit ATwavl F32 var Channel lower wavelength limit ATscps F32 1 Nominal scans per second recorded ATbbtf 132 1 Black body temperature saved type flag O fixed for file 1 table ATbb1 F32 var Black body 1 temperature ATbb2 F32 var Black body 2 temperature ATbbscan 132 var scan at which temp applies for table option ATcalfile C8 32 calibration file name ATcaltab F32 100 calibration values table ATradsc F32 var Channel radiance scaling multiplier ATrunits C8 32 Radiance units ATimgmin F32 var Channels minimum values excluding zero ATimgmax F32 var Channels maximum values excluding overfl
5. The DEM on file sitegrid is already UK99 and contains a file header describing the contents The issue to watch is that the grid completely surrounds the image data if it does not the missing parts will be extrapolated level and parts of the image will not fit a map accurately Watch for the DEM limits message from the program 5 7 using LIDAR DEMs no map fit required If the DEM is generated but not controlled to the local datum eg from scanned photos or LIDAR care has to be taken to avoid what can be large mismatches If the scanner aircraft and the LIDAR aircraft are both gps positioned two choices are possible a if the resultant corrected image does not need to match well an existing map then the LIDAR data must be kept in WGS84 coordinates and use azgcorr ANO mTMw 3 eh lidardem as ex2 ex8 No datum shift if enforced and a transverse mercator projection is used with default parameters EXCEPT the spheroid is WGS84 and the central meridian is 3 west 3 5 8 using LIDAR DEMs best fit required This will require that the LIDAR DEM grid is accurately processed to fit the local map at the desired scale So for a UK example once this is done then ex7 will apply Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 20 20051015 Azimuth Systems User Guide AZGCORR 5 9 controlling output image interpolation Options are provided to do the two passes of the interpolation using one of three met
6. These use identifiers of either TM for the general case of the projection or UTM for the special case adopted by the USGS and Nato for world mapping with a standardised set of grids For UTM following the NATO definition the default in azgcorr uses the following projection parameters with the International spheroid for use in European countries spheroid International Hayford 1910 lao equator Ino central meridian eor 500000 nor 0 for north hemisphere 10000000 south hemisphere sc 0 9996 see mTM for parameter naming details for ease of use mUTM cm allows specification of central meridian by longitude and mUTMZ zone by zone number where cm 180 zone 6 3 To use the Transverse Mercator projection with any other parameter changes use mTM s1 s2 lao Ino sc nor eor note that ALL values MUST be provided as described below in this case EITHER a datum shift must be provided using d7 OR in the rare case that NO datum shift is to be performed then use dN to get passed the valid parameter combination checks in the program For southern hemisphere use mTMS and note that by default mUTMZ or mUTM provide a false northing of 10000000 at the equator mTMS can also be used with mTM full set in which case any value can be used One special case of TM is provided which enables using the standard parameter set with WGS84 the gps spheroid mTMwcm _ note that NO datum shift is needed as WGS84 is used for navigation and
7. metres COalt sl32 var Altitude above local datum metres COroll sl32 var Roll dec degs COpitch sl32 var Pitch dec degs COhead 132 var Heading dec degs COqual UI32 var Interpolation quality OR d flag O interp extrap 1 posn 2 attitude COtime_sc F64 1 Scale multiplier for time COlat_sc F64 1 Scale multiplier for latitude COlng_sc F64 1 Scale multiplier for longitude COhgt_sc F64 1 Scale multiplier for height COroll_sc F64 1 Scale multiplier for roll COpitch_sc F64 1 Scale multiplier for pitch COhead_sc F64 1 Scale multiplier for heading VGroup MAPPING DETAILS This Vgroup is present on Level 3 files only and contains mapping parameters used for final image correction in AZGCORR Vgroup name MAP Vgroup title Mapping details Data item prefix MP Item name type maxv description MPdesc C8 64 Vgroup description Mapping parameters for level 3 MPprog1 C8 40 Vgroup 1st processing program MPsphc 132 1 Spheroid code for map projection MPdatm 132 1 Datum shift code from navigation to mapping datum MPproj 132 1 Map projection code MPIngO F64 1 Longitude of origin MPlat1 F64 1 Latitude of origin or 1st parallel MPlat2 F64 1 2nd parallel MPglat F64 1 Latitude of grid origin MPglng F64 1 Longitude of grid origin MPgx0 F64 1 Grid coordinate at grid origin MPgy0 F64 1 Grid coordinate at grid origin MPscf F64 1 Project scale factor at projection origin MPdshc 132 1 Datum shift code acquisition to mapping datums MPdsVG C8 16 Datum sh
8. typing azexhdf h hdf_file_path at the unix prompt h is optional Will obtain a summary listing to stdout Parameters hg and hd with appropriate VGroup and data item names can be used to restrict the listing to one VGroup or just 1 data item By default vector items listings are limited to 5 items at the start of the vector and the last one if there are more than 5 values To list more of the values use option v to get the required number from the start of the vector or vi to get a selected part from the middle eg azexhdf t1 hdf Will give a summary listing of all items on t1 hdf eg azexhdf hg NV hd NVlat v 100 t1 hdf Will get a listing of the first 100 and last values of the NAV VGroup vector containing aircraft latitudes For image items stored as SDS listing are obtained by using the options bl to select one or more bands and p to define a pixel patch By default the item listed will be ATdata for ATM VGroup and CAimage for CASI VGroup other items can be selected using option d 7 2 Multiplexed vectors Selected vectors can be listed or output to an ascii file multiplexed This is only valid if the items are related and exactly match in length and gaps A typical use of this is to get navigation items or scan sync items vf gives an output file vm selects multiplexed mode and repeated use of vn gives the required items Note this is for none SDS items only eg azexhdf vf nav dat vm vn NVtime vn NVlat vn NVIng
9. vn NVhgt t1 hdf Will obtain a 4 column file with all entries of GPS time latitude longitude and height 7 3 HDF file reformatted to BIL or BSEQ Image items are extracted and reformatted to BIL or BSEQ files with the options BIL or BSEQ to select the file format along with an appropriate file path to contain the output The following optional parameters can be used to modify the output d to select a none default item ATM is ATdata CAS is CAimage bl to select one or more bands p to limit pixels and lines Bs to get a summary statistics file and Bh to get a histogram for each selected band Bv will obtain extra coordinate details for level 3 files BIL and BSEQ output files data entries are in the same format as level 1 files ie binary unsigned integers Pixels are output with file indexed zero first and lines with line indexed zero first Bands are output in the order requested by parameter bl eg bl 5 3 2 1 would give these three bands in order 1 2 3 on the output file if the file was BIL the sequence would be line O band 5 pixels 0 ton line O band 3 pixels 0 ton line O band 2 pixels 0 ton line 1 band 5 aseen etc Line and pixel order imply that a level 1 file will be in flight direction down the file with pixel zero on the right By default a level 3 north up file will be going north down the file with pixel zero to the west Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 38
10. Micomm C8 128 Comments Mlifnum 132 1 CASI field tape file number Mlaper 132 1 CASI used aperture Mlscanner C8 8 Scanner name ATM or CASI Mislimit 132 1 Site limit type flag O none 1 time 2 scan 3 both Misday 132 1 Day number of site start time 1 366 Mistime 132 1 Time of site start HHMMSS Mletime 132 1 Time of site end HHMMSS Mlsscan 132 1 Scan number at site start Mlescan 132 1 Scan number of site end Mllimits C8 128 description of site limits VGroup NAVIGATION Contains observed navigation from aircraft survey instruments and base reference station Up to two sets of independent navigation sets can be saved with position and attitude with each set having independent timing All times in seconds are consistent and are used to link navigation observations and scans GPS data is inserted by azjps or azimport and scan sync by azjps azatm or azcaschk VGroup name NAV Vgroup title Navigation Data item prefix NV Item name type maxv description NVdesc C8 64 Vgroup description GPS navigation and scan synchronisation data NVprog1 C8 40 Vgroup 1st processing program NVprog2 C8 40 Vgroup 2nd processing program NVprog3 C8 40 Vgroup 3rd processing program NVsys1 C8 40 Prime aircraft survey navigation system NVsysti C8 40 Prime system infomation NVsys2 C8 40 Secondary aircraft survey navigation system NVsys2i C8 40 Secondary system infomation NVsys3 C8 40 Third aircraft survey navigation system NVsys3i C8 40
11. Third system information NVbase C8 40 Base reference station navigation system NVbasei C8 40 Base information NVposii C8 40 position set 1 information NVatt1i C8 40 attitude set 1 information NVpos2i C8 40 position set 2 information NVatt2i C8 40 attitude set 2 information NVspher C8 40 Spheroid name for aircraft navigation system NVdatsh C8 40 Datum shift applied to aircraft navigation system NVtbase C8 40 basis of all timing NVacor 64 1 vector of aircraft nav posn to scanner offset Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 48 20051015 Azimuth Systems User Guide AZGCORR NVut2gt 64 1 time correction used to convert NMEA UTC times to GPS time in seconds NVjday 132 1 Year day for site start NVstime 132 1 Time of site start HHMMSS NVetime 132 1 Time of site end HHMMSS NVtime 132 var Time of position set 1 observations GPS dec secs NVutc sl32 var Time of position set 1 observations UTC dec secs NVlat sl32 var Latitude dec degs NVIng sl32 var Longitude dec degs NVhgt sl32 var Spheroid height metres NValt sl32 var Recorded altitude above local datum metres NVqual UI32 var position quality flags NVasecs sl32 var Time of attitude set 1 observations dec secs NVroll s132 var Aircraft roll positive right wing down dec degs NVpitch sl32 var Aircraft pitch positive nose up dec degs NVhead sl32 var Aircraft heading 0 360 clockwise from true north dec degs NVaqual
12. UI32 var attitude quality flags NVtime2 sl32 var Time of position set 2 observations GPS dec secs NVlat2 sl32 var Latitude dec degs NVIng2 sl32 var Longitude dec degs NVhgt2 s132 var Spheroid height metres NValt2 sl32 var Recorded altitude above local datum metres NVqual2 UI32 var position set 2 quality flags NVasecs2 sl32 var Time of attitude set 1 observations dec secs NVroll2 sl32 var Aircraft roll dec degs NVpitch2 sl32 var Aircraft pitch dec degs NVhead2 sl32 var Aircraft heading dec degs NVaqual2 UI32 var attitude set 2 quality flags NVsctcor F64 1 Time correction from nav observation to scan observation NVscnum s 132 var Scan number see below NVscsecss 132 var Scan synchronisation time GPS dec secs see below NVtime_sc F64 1 Scale multiplier for time NVasecs_sc F64 1 Scale multiplier for attitude time NVlat_sc F64 1 Scale multiplier for latitude NVIng_sc F64 1 Scale multiplier for longitude NVhgt_sc F64 1 Scale multiplier for height NVroll_sc F64 1 Scale multiplier for roll NVpitch_sc F64 1 Scale multiplier for pitch NVhead_sc F64 1 Scale multiplier for head NVscnum_sc F64 1 Scale multiplier for scan number NVscsecs_sc F64 1 Scale multiplier for scan sync time Notes 1 Navigation vectors are stored as scaled integers format s132 file values are to be multiplied by the appropriate scale to obtain a double precision floating value 2 Spheroid and datum codes are documented in Appendix A 3 i
13. by using a constant correction to the aircraft height using either uh or uo items 5 12 4 position adjustment The final image position relative to map features should be adjusted after other errors are minimised Corrections can be made in either map projection grid using u or WGS84 geographic coordinates using uow If the former is used the equivalent correction is listed as lat lob height increments which may then be applied to update the basic navigation or for use before a different map projection Applying Corrections It is suggested that a reasonable subset of the lines 2000 4000 and 3 bands for an RGB image are used for initial tests A base image with no adjustments should be made against which all changes can be compared Using the guide above adjustments should be made to minimise any apparent errors If vector data is available estimates of corrections can be made Offshore no linear features or no maps Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 23 20051015 Azimuth Systems User Guide AZGCORR Corrections to these images can only be made if these are adjacent and overlapping flight lines Corrections are made until common features match along the overlap zone of the lines Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 24 20051015 Azimuth Systems User Guide AZGCORR 6 azgcorr run options and parameters The description below expa
14. image See TIF for band order note GeoTIFF files can be input into most of the main remote sensing image handle packages eg ERDAS ERMAPPER etc ERDAS from ver 8 5 will accept and allow viewing of more than 3 bands in the file GeoTIFF ver 1 1 4 in azexhdf 2 0 0 has some restrictions in defining map projections which affect some local European projections For the UK currently only the basic pre 1995 method for UK National Grid is supported When images are transferred to ERDAS and used with other images or vector data this should be remembered 7 7 Limitations and error messages azexhdf may not work correctly and may well crash if the input hdf file was created by a previous program run that terminated with an hdf error This is one of many deficiencies in the HDF system which is unable to detect corrupted or improperly closed files azexhdf will correctly report if an input file is missing or not an HDF file It will then terminate Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 39 20051015 Azimuth Systems User Guide AZGCORR Appendix A Commonly used Datum Shift and Spheroid values Datum shift d and map projection m options both may require numeric values for spheroids and datum shifts commonly used values are supplied below These are supplied without any claim as to their accuracy it is the user s responsibility to verify accuracy and relevance to their use Spheroid values
15. mapping projection therefore NO d parameters are required TM and UTM details option mUTM cm UTM with central meridian TM set to UTM with supplied central meridian longitude cm signed decimal degrees option mUTMZ zo UTM to zone zo 1 60 Zones are 6 degrees wide and numbered 1 to 60 1 is 180 west to 174 west with central meridian at 177 west UK is in zones 30 3 west and 31 3 east option mTMw cm TM using WGS84 spheroid Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 27 20051015 Azimuth Systems User Guide AZGCORR This option is provided to allow a quick look at non UK data without having to fill in all the parameters to keep the map projection in WGS84 spheroid option mTM s1 s2 lao Ino sc nor eor Comprehensive TM Transverse Mercator with user supplied parameters si spheroid code or semi major axis a metres O INT 1 Airy 3 WGS84 s2 semi minor b or reciprocal flattening f metres or unit less or eccentricity e 2 set this to 0 if s1 is a spheroid code lao projection origin latitude degs Ino central meridian longitude degs abbreviated to cm sc scale factor at Ino typically 0 9996 nor eor grid coords at origin and cm metres No defaults are provided so ALL parameters have to be supplied option TMS forces use of southern hemisphere for TM may be used with mTM and mUTM option mLAM h s1 s2 lao Ino eor nor la1 la2 Lam
16. resolution there may be several tiles covering the required area Composited rows are selected form the tiles to allow single pass interpolation to avoid tile join artifacts Geographic grids first may optionally have a geoid spheroid correction added or removed they are then optionally datum shifted and transformed to the mapping projection The projected grid is then interpolated to the final required DEM grid interval Generally this is transparent to the user so if the input is SRTM and the mapping is OSGB then the appropriate operations are automatically applied Already gridded data is selected to cover the required DEM and interpolated to suit LIDAR point cloud data is optionally datum shifted and map projected or re projected and then gridded using different methods depending if the data is sorted xy or time ordered In each use of interpolation gaps in the data are allowed for there are parameters defining gaps and good runs of data Small gaps are filled in but large ones are retained When all grids have been added a final pass in made to fill in any gaps that are smaller than user defined limits so small gaps will be filled in and large gaps left Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 11 20051015 Azimuth Systems User Guide AZGCORR The merged DEM can now saved to an external file for reuse or display Several save formats are provided eg GeoTIFF ENVI etc Provision is also m
17. this allows data from different instruments to be compared and used for combined calculations Navigation data for Level 1B has to be acquired from suitable instruments or processed to achieve ECEF coordinates GPS data both position and attitude as obtained from a GPS receiver is inherently ECEF INS and combined INS GPS needs post processing to allow for INS drift local gravity anomalies conversion from sensor frame to vehicle frame etc In all cases for the highest accuracy GPS position needs correction against a fixed base station ie using techniques of Differential or Kinematic processing Inputs to azgcorr are run time parameters from the command line Level 1B HDF Level 2 HDF ora combined Level 1B HDF and related BIL BSEQ image file Outputs are a brief run listing and a Level 3 file Details the scanner optics are obtained from the command line or HDF file defaults Levels refer to the NASA definition of satellite or airborne image processed status The basic definition of these are Level 0 raw instrument acquired data no corrections Level 1A radiometric corrections applied Level 1B as 1A but with synchronised per scan geo location data included Level 2 products derived from Level 1 data Level 3A Level 1 data geo corrected Level 3B as 3A but with ground control used for precise location Level 3A processing corrects the image data and interpolates an output image on a regular grid ina recognised map projection coordinate
18. 1 ATrmedia C8 64 recording media ATtype C8 8 Daedalus ATM type eg 1268 ATid C8 32 ATM ID ATfov F32 1 Field of view dec degs ATfovp F64 3 details of reduced filed of view see below ATpixfov F32 1 Pixel field of view ATpixrec 132 1 Pixels per scan recorded ATpixred 132 1 Pixels per scan reduction method 0 none 1 average 2 nearest ATpixsav 132 1 Pixels per scan saved ATsscan 132 1 Target start scan ATescan 132 1 Target end scan ATchan 132 1 Channels bands recorded ATbands 132 var Channels bands saved to HDF file see note 3 below ATbpix 132 1 Bits per pixels recorded ATwavu F32 var Channel upper wavelength limit ATwavl F32 var Channel lower wavelength limit ATscps F32 1 Nominal scans per second recorded ATbbtf 132 1 Black body temperature saved type flag 0 fixed for file 1 table ATbb1 F32 var Black body 1 temperature ATbb2 F32 var Black body 2 temperature ATbbscan 132 var scan at which temp applies for table option ATsbb1 F32 var Black body 1 set temperature ATsbb2 F32 var Black body 2 set temperature ATvbb1 F32 var Black body 1 viewed DN average ATvbb2 F32 var Black body 2 viewed DN average Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 52 20051015 Azimuth Systems User Guide AZGCORR ATsync F32 var 2 ATcal C8 16 indicates if data is calibrated ATcalver C8 16 version of calibration file ATcalfmt C8 16 format layout of calibration file AtTcalfile C8 32 calibrat
19. 20051015 Azimuth Systems User Guide AZGCORR directions can be changed in level 3 processing Option I can ve used to reverse the line order convention for output to a file 7 4 Sun raster output A SunRaster format file can be created from 1 or 3 selected bands to give an image viewable using utilities such as imagetool or XV Note that if the selected image is beyond a certain size or contains too may colour levels these utilities will resample and remap the pixels Option S selects the output format and provides the output file c or m provides the band from the HDF file and selects RGB colour or monochrome output file format p can be used to restrict the image patch eg azexhdf ti hdf S a sunr c 532 Will obtain a SunRaster RGB file for bands 5 for red 3 for green and 2 for blue of the whole default image item on t1 hdf 7 5 TIFF output ATIFF file containing 1 3 or more bands can be created using the option T fp Data limiting options as for BIL apply to select bands pixels and lines Pixel format is limited to UINT16 For most display packages that have no band to colour channel control bands must be selected in order RGB to give correct colours The created file can be used in many image display packages but not all can handle more than 3 bands 7 6 GeoTIFF output A GeoTIFF output file can be created as for TIF but can only be from a level 3 file as the GeoTIFF file requires geolocation data for a rectangular
20. 8 or even 10 to avoid gaps at the image edge The nature of the sampling process in both line scan ATM and CCD CASI scanners results in the DN value obtained for a pixel being a measure of the reflection source by up to two pixels from the centre of a given pixel and controlled by the pixel response function sort of Gaussian When interpolating observed scan data to get a rectilinear output no interpolation method is any more accurate than another just different and all only an approximation to the value that would be obtained if the output pixel was measured directly With this in mind it is suggested that any scientific operation eg atmospheric correction is performed on the Level 1 data and geometric correction applied to this Level 2 product Any none scientific operation eg classification is performed on the interpolated geometric corrected image where pixels are in their correct geometric relation with each other 3 7 CASI and other CCD scanner corrections Data from this type of scanner may require some extra processing options to cater for the three possible data components recorded in the different operating modes of the instrument image data spectral data and ILS Briefly the data types consist of rec mode item content SPATIAL image several bands of continuous pixels ILS same number of bands of single pixels SPECTRAL image many bands of spaced out pixels SRC single band continuous pixel image for sce
21. AZIMUTH SYSTEMS UK Airborne Remote Sensing Hyperspectral Direct Georeferencing package AZGCORR User s manual azgcorr version 5 0 0 July 2005 azexhdf version 3 0 3 April 2005 Last revised October 2005 draft version 4 7 05 NB dem parameter description in section 6 not complete diagrams not included Copyright c Azimuth Systems UK 1996 2005 All rights reserved Azimuth Systems User Guide AZGCORR 3 1 3 2 3 3 3 4 3 5 3 6 3 7 3 8 3 9 4 1 4 2 4 3 4 4 4 5 4 6 5 1 5 2 5 3 5 4 5 5 5 6 5 7 5 8 5 9 5 10 5 11 5 12 6 7 New items and updates in this version Introduction Summary of functionality Geo correction concepts in azgcorr Goals for correction Navigation relation to Datums and Spheroids Map projections Digital Elevation data Time Image Interpolation CASI and other CCD scanner corrections Viewing the results Geocorrection in the real world Using azgcorr Introduction Internal data files used by azgcorr External data files used by azgcorr System requirements Installation on Solaris or Linux Practical aspects of running the programs Applications of azgcorr to obtain online program help basic correction changing the map projection no datum shift required changing the datum shift and map projection improving mapping accuracy without a DEM using DEMs all consistent coordinates using LIDAR DEMs no map fit required using LIDAR DEMs best fit
22. Bands not saved will not take space on the HDF file Note the VGroup items ATwavu ATwavl ATgains ATradsc ATimgmin ATimgmax ATimgzer ATimgovr will have the same dimension as ATbands and the contents will refer to the same bands as the numbers in ATbands VGroup CASI Contains CASI scanner recording parameters and recorded calibrated or geometrically corrected image data stored as 16 bit integer to level 1b and either 16 bit integer or 32 bit floating for level 2 and level 3 Up to three sets of image data may occur Image SRC and ILS see ITRES CASI documentation Contains Vgroup name CAS Vgroup title CASI Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 53 20051015 Azimuth Systems Data item prefix Item name CAdesc CAprog1 CAprog2 CAprog3 CAprog4 CAserial CAswver CAexa CAfnum CAconfig CAsday CAstime CAmode CAg CAinteg CAapert CAfapert CAoaxis CAfov CAfovport CAfovpix CApsfov CApside CAsscan CAescan CAlooks CAlooksp CAlookc CAsumdch CAsrcpres CAsrcbands CAsrcchan CAsrcpix CAilspres CAilsbands CAilspix CAbstart CAbend CAwave CAwavh CAcalfile CAradsc CArunits CAiunits CAimgmin CAimgmax Caimgzer CAimgovr CAsrcmin CAsrcmax CAsrezer CAsrcovr CAilsmin CAilsmax CAilszer CAilsovr SCimtype SCorder SClndir SCtiles SCbands SCpixels Remote Sensing Scanner Processing System Version 3 00 type C8 C8 C8 C8 C8 132 C8 C8 132 C8 132
23. IL and image item listings option ph does image listing in hex Switches image listing between integer and hex option pbseq if present does image list in BSEQ order If not present default image list in BIL order option po only image listing done Suppresses listing of other HDF data items Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 35 20051015 Azimuth Systems User Guide AZGCORR option option m option bO option bo bn option option option option option item option sten option fmt option option no r output DN values as radiance using default scaler Default is to save image items unchanged from the HDF file rm m user supplied multiplier for DN scaling for BIL output user supplied multiplier bl bO b1 1 select bands to be converted to output list of band numbers 1 bands and in the order for saving br b0 bn select bands by range bands will be saved from bO to bn l line order reversed on output to files Scan lines are output by default as HDF levels 1 and 2 scan 0 first HDF level 3 northern most scan first If I is present this order will be reversed Vie vector saving listing options vf fp filepath for complete vector output V max max items to list for vectors in summary listing def 1 NB this is for listings only vn item HDF VData vector data item name VData name repeat use for severa
24. International 9 6378388 00 297 00 Hayford 1910 Airy 1830 6377563 3963534 299 32496459380 UK National Grid Clarke 1866 6378206 400 294 9786988 n Clarke 1880 6378249 200 293 466021 IGN Krassovsky 1940 6378245 000 ee Australian National 6378160 000 820s Ghana National 6378295 000 eof OS GB GRS80 6378137 000 298 25722154381 el IGRS80 6378137 000 298 257222101 o Notes a Code for spheroid as displayed as item MPsphc in the Mapping Vgroup MP of an azexhdf listing Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 40 20051015 Azimuth Systems User Guide AZGCORR Datum shifts These are all FROM WGS84 TO the named spheroid d s are in metres r s in seconds sc in ppm sonore eT wy Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 41 20051015 Azimuth Systems User Guide AZGCORR Appendix B Map projections and required parameters azgcorr has several built in map projections to convert navigation usually from WGS84 geodetic coordinates to a local map projection grid These projections are described and their parameters are summarised in the tables below Transverse Mercator Is a cylindrical projection with the cylinder perpendicular to the earth s north south axis and the point of contact with the earth at the central meridian Has special properties useful for survey purposes with local scales and directions being
25. Mercator projection has been selected with a user central meridian of 7 degs west A fictitious 7 point datum shift has been supplied and the default spheroid of International 1909 6378388 297 has been used for both the datum shift and projection Origin of the projection is at the equator and grid coordinates go from 0 at the equator northwards and form 50000 at 7 degs west Commonly used datum shift and spheroid values are described in Appendix A 5 5 improving mapping accuracy without a DEM Positioning based on WGS84 provides the latitude and longitude of the scanner as well as its height above the WGS84 spheroid With the default settings azgcorr projects the corrected image to zero above the spheroid for most sites this will be in error so for coastal or relatively flat land sites where no DEM is available an improvement in mapping accuracy can be obtained by applying a spheroid to geoid correction form the internal tables or an external file azgcorr hsu then as ex2 ex5 azgcorr hsu es gsepfile then as ex2 ex6 The first example assumes UK based data so the internal table can be used the second supplies a file which may cover any of the globe 5 6 using DEMs all consistent coordinates As discussed in detail in section 3 4 above DEM grids have to be consistent with the datum shift and map projection selected This will be the case for DEMS obtained form local maps or mapping agencies azgcorr mUK99 osgb99 eh sitegrid then as ex2 ex7
26. ade to offset DEM values to allow viewing in a general image display program that expects black to be zero This offset is allowed for in subsequent azgcorr use 3 5 Time Time only becomes important when the Level 2 options to calculate pixel view and solar illumination angles are used Except for these solar calculations for which UTC is required GPS time of day is used throughout for identifying and merging data Full details of time will be available with the integrated release of level 2 processing in azgcorr 3 6 Image Interpolation In the current release three image interpolation options are provided a bi cubic b bi linear and c nearest neighbor The first two methods will produce pixel values not in the input image method c will not generate extra values and must be used for classified images In all cases image data is only used if it has DN values between the upper and lower limits stored in SCimover and SCimunder respectively User control is also provided for defining the size of gaps that will be interpolated or filled nearest neighbor and the minimum number of pixels considered to be a good run Both these parameters have limited importance as they only affect the edge of images where the pixel distortion makes the data of little value and generally can be left to default Care must be taken when a small pixel size is used together with large aircraft motion in this case the gap parameter may need to be increased to 6
27. al SRC image present flag O no 1 yes SRC no of bands band used for src SRC no pixels ILS present flag O no 1 yes ILS no of bands ILS no of pixels band start of image data band end of image data wavelength centre wavelength half bandwidth Calibration file name Radiance scaling multiplier Radiance units ILS irradiance units Image bands minimum excluding zeros Image bands maximum excluding overflows Image bands zeros Image bands overflows SRC band minimum excluding zeros SRC band maximum excluding overflows SRC band zeros SRC band overflows ILS bands minimum excluding zeros IILS bands maximum excluding overflows ILS bands zeros ILS bands overflows Image type flag O as source 1 resampled Pixel order flag O I to r 1 r to in direction of lines increasing Scan line direction flag O flight direction 1 north up Tiles in image 0 not tiled single image gt 0 number of tiles Bands in image Pixels in image c Azimuth Systems 1996 2005 54 20051015 Azimuth Systems User Guide AZGCORR SClines 132 1 Lines in image SCpixfmt 132 1 Pixel format flag O 8bit unsigned 1 16bit unsigned SCHDFfmt 132 1 Pixel HDF number format flag see HDF documentation for details SCimover F32 1 flag value indicating overflowed values see general note 2 SCimunder F32 1 flag value indicating underflowed or missing values see gen note 2 SCpixbytes 132 1 Bytes per pixel SCposn 132 1 Position d
28. ane 132 1 Image view y plane position metres SCposcorr F64 var Image position adjustments see general note 7 SCposimag F64 var Image position coordinates for SCposn 1 see general note 5 SCposscan 132 1 Position info per scan content flag SCsused 132 var scans used in level 3 image field scan numbers SCbused 132 var bands used in level 3 image level 1 band numbers SCpxyn 132 1 No of pixels per side of tile SCpxy_sc F64 1 Image xy scale multiplier ATimgxy 132 var Image tiles coordinate list ATdata SDS 3xvar Image data ATM notes 1 Items sbend rgyro hddt and cct are specific to the original ATM system 2 ATfov and ATfovp if ATfov 0 0 then a reduced field of view has been applied to the original ATpixred is the reduced number of pixels ATfovp 0 this same number ATfovp 1 port field of view angle from nadir and ATfovp 2 starboard field of view angle 3 From Jan 2003 ATM level 1 files may contain less than the total number of bands recorded The basic ATM recorded by the AZ16 data system acquires 11 bands 1 11 if all bands are saved then ATbands will contain 11 values from 1 11 or optionally ATbands will not be present and SCbands will 11 If it contains less then SCbands will be lt 11 and ATbands will have the list of saved bands these will be numbered as for the original acquired bands AND will be in the user requested order NOT increasing band number order There may be as few as 1 band for a thermal only flight
29. ass interp is cubic sm smoothing option itg thinning option on second pass interpolation g multiples of pixel spacing default 0 5 Pixels are omitted if closer together than g option g gm gr Image gap control gm gap size in multiples of pixel size ie gap metres gm pix_size gr good data run which will be interpolated These controls only affect the edge of the image as gaps rarely occur elsewhere In general the defaults should be used Defaults gm 4 gr 4 e Digital Elevation Model DEM control option e fn Digital Elevation file fn DEM file path may be repeated 8 times file s may be NTF contour OR grid OR internal grid format but not mixed option eg gr DEM grid increment For use with NTF contour files defines the saved DEM grid increment should be gt 2 pix inc Default 10 metres option ef DEM force slow search for ground intersection This option is occasionally needed in areas of rapid topographic change steep slopes Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 31 20051015 Azimuth Systems User Guide AZGCORR option ez v DEM fill grid edge V value to fill empty grid edge nodes Default fill with nearby values option ed or c r xm ym xx yx gi flat file ascii DEM definition This defines the contents of a flat file containing DEM values Files may have no header in which case e fn gives the filename or a header may be used to
30. ata relation flag 0 posns per scan 1 posns per image SCaxes 132 1 Coordinate axes for position flag O along fit dir 1 N up SCxypix 132 1 relation of coordinates to pixel flag O centre 1 BL SCpixwid F32 1 Pixel width x or scan direction metres SCpixhgt F32 1 Pixel height y or flight direction metres SCviewty 132 1 Image view type flag see general note 4 SCvplane 132 1 Image view y plane position metres SCposcorr F64 var Image psotion adjustments see gernal note 7 SCposimag F64 var Image position coordinates for SCposn 1 see general note 5 SRCposimag F64 var SRC image position if different from Spectral or Enhance Spectral data image SCposscan 132 1 Position info per scan content flag SCsused 132 var scans used in level 3 image field scan numbers SCbused 132 var bands used in level 3 image level 1 band numbers SCpxyn 132 1 No of pixels per side of tile SCpxy_sc F64 1 Image xy scale multiplier CAimgxy sl32 var Image xy coordinates CAsrcxy sl32 var SRC xy coordinates CAilsxy sl32 var ILS xy coordinates CAimage SDS 3xvar Image data spectral or spatial bands CAsrc SDS 3xvar SRC data scene recovery for spectral mode CAils SDS 3xvar ILS data CASI notes 1 Descriptions starting with indicate values transferred without alteration from the CASI data file Full details can be found in CASI documentation General Notes 1 Data types C8 CHAR8 8 bit characters used for text strings which are zero termi
31. ates for SCposn 1 see general note 5 SCposscan 132 1 Position info per scan content flag SCsused 132 var scans used in level 3 image field scan numbers SCbused 132 var bands used in level 3 image level 1 band numbers SCpxyn 132 1 No of pixels per side of tile SCpxy_sc F64 1 Image xy scale multiplier ATimgxy 132 var Image tiles coordinate list ATdata SDS 3xvar Image data ATM notes 1 Items sbend rgyro hddt and cct are specific to the original ATM system VGroup ATM2 Version for AZ16 recorded data note that some parameters have been changed from numerical flags to descriptive text to make the Vgroup more readable Contains ATM scanner recording parameters and recorded calibrated or geometrically corrected image data stored as 16 bit integer to level 1b and either 16 bit integer or 32 bit floating for level 2 and level 3 Level 1 data is inserted by ATM_1 Data recorded with the DEI320 has 12 channels and from the AZ16 11 channels Vgroup name ATM2 Vgroup title ATM2 Data item prefix AT Item name type maxv description ATdesc C8 64 Vgroup description ATM scanner details calibration and data ATprog1 C8 40 Vgroup 1st processing program ATprog2 C8 40 Vgroup 2nd processing program ATprog3 C8 40 Vgroup 3rd processing program ATprog4 C8 40 Vgroup 4th processing program ATsbend 132 1 Sbend correction applied in scanner flag O no 1 yes Note 1 ATrgyro 132 1 Roll gyro correction applied in scanner flag O no 1 yes Note
32. ault installation so home is home fred Data is to be stored in separate directories for dems atm and casi so the following are created and the appropriate data copied to them home fred dems has files sphsep erewhon dem home fred atm has file a1270211b hdf for line 21 day 127 home fred casi has file c1270211b hdf for line 21 day 127 to process the atm data change to that directory and run azgcorr to create a geocorrected pseudo RGB image of bands 5 3 and 2 cd home fred atm azgcorr p 55 bl 532 1 es home fred dems sphsep e home fred dems erewhon dem 1 a1270211b hdf 3 a1270213b hdf NB this is only an example and files paths may be different Other examples are in section 5 below 4 5 1 Some of the problems that may be encountered on installation and first use a system message command not found when azgcorr is typed The program in not in the correct directory check where it was installed and make sure that directory is in the search path type PATH assuming the use of sh or bash and the search path will be listed b system message Permission denied when azgcorr is typed The program has been copied form a CD and does not have execute permission Go to its directory and type chmod x azgcorr c system message azgcorr error while loading shared libraries libjpeg so 6 cannot open gt shared object file gt No such file or directory It may refer to other system libraries this will need to be ref
33. avoid using this ed option in this case use eh to give the file name or data order 0 rows x S gt N 1 rows N gt S c cols r rows xm ym SW corner coords xx yx NE corner coords gi grid increment grid values on file must be separated by space s and may have decimal points NB only ONE file may be present option eh fn flat file with header fn DEM file path for flat file with a header header is the ed items separated by spaces eg 0512 1024 0 0 511 1023 1 0 option es fn fn geoid spheroid separation grid file path if fn NO no geoid spheroid correction will be applied Default if es is not present is to use program built in g s values which cover UK SW 49 75 N 7 5 W to NE 60 75N 2 75E Sites outside this range must use a g s file option n Navigation control option nac pr h sign control of attitude items p r h 0 for use item without sign alteration 1 for use with signs reversed 2 for don t use ie set attitude item to zero nav may them be used to give a constant value NB normal sign convention assumes pitch is ve nose up roll is ve port wing up head is ve clockwise from nose option ns reverse scan direction scan direction is assumed to have pixel 0 from the input file on the starboard side of the field of view option u User view vector controls Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 32 20051015 Azimuth Systems Us
34. band RGB set is produced Interpolation is left to cubic default c first azexhdf just generates a content listing of the level 3 HDF file d second azexhdf creates a GeoTIFF file of the level 3 3 band image note this has 16 bits per band this will be compatible with ERDAS 8 5 ERMAPPER etc 5 12 User controls for view vector adjustment From version 4 5 0 user accessible controls are provided to adjust the final geocorrected image to allow for navigation synchronisation or instrument view vector pointing errors These controls are grouped in the u command line options and are described in detail in section 6 below The controls provide four main functions which adjust 5 12 1 the time relation between navigation and image synchronisation 5 12 2 the 3D tilt or projection of the pixel lines forming the image 5 12 3 the xy scale of the complete image 5 12 4 the xy position of the complete image No provision is made for random stretching or rubber sheet fitting this is considered inappropriate at this stage of processing and is left to general purpose image handling packages In general the errors requiring these controls will have been minimised in post flight processing prior to user data access For a variety of reasons this may not be sufficiently accurate for some applications or the end user has subsequent map GIS or survey data that needs to be fitted 5 12 0 Introduction to airborne remote sensing navigation This section
35. bert Conical Lambert Conical Orthomorphic with one or two parallels s1 s2 lao Ino eor nor as TM above h hemisphere N north S south la1 la2 two standard parallels lats if la1 la2 single parallel projection used option OM Oblique Mercator option OM do s1 s2 sc xor yor lac lai In1 la2 In2 if do 0 OM do s1 s2 sc xor yor lac Inc azc if do 1 do defining option 0 for centre and 2 points on centre line 1 for centre and azimuth of centre line si spheroid code or semi major axis s2 semi minor axis b reciprocal flattening f or eccentricity e 2 Sc scale factor at centre of projection xor yor grid coordinates at origin lac Inc lat long at centre la1 In1 first point on centre line la2 In2 second point on centre line azc azimuth of centre line east of north option RSO Rectified Skew Mercator parameters as for Oblique Mercator above option NZ New Zealand projection Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 28 20051015 Azimuth Systems User Guide AZGCORR New Zealand projection on International spheroid Hayford 1910 no parameters option DUTCH Netherlands National Grid Rijksdriehoeksmeting RD projection on Bessel 1841 spheroid no parameters a Corrected image alignment relative to map option an North up Default if a is not used option af Rectangle centered on flight line option aaz az user clockw
36. bil by selecting Bs a second file is created a1raw bil stats which may be input to a user program to obtain the details of the BIL file without having to manually transfer them see Appendix userprogram optionally uses the stats file and input image data from a1raw bil performs some calculation which for this example only creates 1 band and outputs the result image to a1new bil It does matter if this file is described as BIL or BSEQ as it only has one band both will be identical The azgcorr run still requires the original level 1b HDF file a1 hdf as well as the user created BIL file a1new bil and the parameters describing this file These indicate there is 1 band data in floating point no re scaling required and standard blank area infill required Corrected output will be to a3 hdf Note that a current restriction is the number of lines and pixels must the same throughout so the user program must not change the number of lines or pixels 5 11 typical complete run Batch script file contains rm a3 hdf azgcorr mUK99 uk99grid eh DEMforsite p 2 2 bl 5 3 2 1 1 a1l hdf 3 a3 hdf Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 21 20051015 Azimuth Systems User Guide AZGCORR azexhdf a3 hdf azexhdf bi 123 1 ha3 hdf G a3 tif a The old level 3 files are first removed b azgcorr run does correction on UK National grid 1999 version and uses a local DEM Pixel size is 2 metres and a three
37. ction georeferencing results 4 1 Using azgcorr Introduction Expands the description of the use of unix command line programs Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 2 20051015 Azimuth Systems User Guide 4 4 System requirements System requirements for using the Sun and Linux versions of the programs 4 5 Installing software new Covers typical software installation and problems that may be encountered 5 12 User controls for view vector adjustment new Description of user controls for precise georeferencing 6 Program execution Options and Parameters see options for Transverse Mercator Projection use mTM and mUTM View vector adjustment u new DEM handling e Appendix B Map projections and parameters new Filled in with basic details of projection parameters as well as some references for further reading Appendix D AZSPS Level 1 and Level 3 HDF file details Description of items related to view vector adjustment AZGCORR Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 3 20051015 Azimuth Systems User Guide AZGCORR 1 Introduction to azgcorr This program has been developed and refined over a the passed 9 years and is the result of the author s experience with airborne remote sensing since the 1980s The basic method used in azgcorr was first tested on images from an ATM scanner in 1989 using hand adjusted navi
38. ction is not only important for visual improvement of georeferenced images but is critical for scientific analysis of the imagery this aspect is discussed in other literature The result of using only radiometric calibrated data is that images will show effects like limb brightening showing as a change of density across the track of the aircraft ie in the scan line direction Survey lines mosaiced with these effects still present will appear to be patchy across the lines Variation in overlapping images areas may vary from very low to quite big differences in pixel values due to the combination of variation in view vector angle from nadir aircraft attitude at acquisition and change in illumination due to different times of acquisition on the different lines To remove or at least minimise these effects it is necessary to first radiometrically calibrate the image then apply Atmospheric Correction and finally do geocorrection in azgcorr Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 14 20051015 Azimuth Systems User Guide AZGCORR 4 Using azgcorr 4 1 Introduction As supplied azgcorr is a unix command line program is used as any other unix utility and complies with the standard syntax program_to_run parameter_1 parameter_2 etc An example of the simplest run is azgcorr p 55 1 a1 hdf 3 a3 hdf This will use navigation and level 1 data on file a1 hdf and correct and output an image to file a3
39. d Geodetic Survey Dutch Developed specifically for the Netherlands and does a single step transformation of datum shift and projection from geodetic WGS84 coordinates to grid and visa versa reference formulas obtained from T G Schut Transformatie van rechthoekige RD coordinaten naar geografische coordinaten op de ellipsoide van Bessel In NGT Geodesia juni 1992 Ministry of Transport Public Works and Water Management Directorate General for Public Works and Water Management Survey Department P O box 5023 NL 2600 GA Delft Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 42 20051015 Azimuth Systems User Guide AZGCORR Projection Parameters version azgcorr controls projection parameters for user control none Cc A Zz 9 a c mUTM mTMS mo Foo m s1 s2 lao Ino sc la1 la2 FmOM s2 sc xor yor lac lat In1 la2 In2 ee SS parameter description Si pheroid semi major axis m s2 spheroid semi minor axis m or reciprocal flattening unitless or eccentricity e 2 lao ffatitute origin degs Ino fongitude origin degs lac Inc azc Oblique Mercator defining centre line by start point and azimuth lat long degs azimuth degs 0 360 clockwise from north Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 43 20051015 Azimuth Systems User Guide AZGCORR Notes a Code for map projection a
40. d in a level 1 file this will be a level 1a if no navigation is present or 1b with navigation a file will only contain data for one scanner and for one site b a Level 1b file processed by azgcorr may be used to generate a Level 3 file this will contain all the navigation and meta data items of the Levelib it will NOT have the level 1 image data present it will have the geocorrected image data it will have a mapping MP vgroup with mapping details used in the geocorrection External data files used by azgcorr azgcorr may be supplied with a few binary files containing correction grids for certain map projections and for spheroid to geoid corrections The user only has to supply the appropriate parameter that gives the file path to these Other files which may be needed are user supplied digital elevation models DEMs These may be from topographic mapping LIDAR or other sources Details of their use is in the section 3 4 on how to use DEMs as well as the DEMS in Option and Parameters below 4 4 System requirements Versions of azgcorr and azexhdf can be supplied for use on Sun workstations under Solaris version 2 3 or higher and Intel AMD compatible x86 PCs running any version of Linux with kernels of 2 4 and above Linux versions will run an AMD 64 bit processors with no changes provided the 32 bit libraries are present in the LD library search path Using earlier versions may cause shared system library incompatibilities so users should check
41. d or a INS AHRS IMU that is NOT mounted on the scan head AND the scan head has shock mounts or a stabilised platform then the measured attitude WILL NOT be that of the scan head and AZGCORR WILL NOT produce optimum results 3 2 Navigation relation to Datums and Spheroids All navigation on the earth s surface is referenced to a set of axes and a model which describes the static and dynamic geometry of the earth and navigation platform this is a geodetic datum For the sake of this discussion we can ignore all parameters except earth geometry and time For brevity a datum is given a name or even a mnemonic throughout the world there are several hundred different datums Current GPS datum is called WGS84 World Geodetic System agreed in 1984 Spheroid To make position observation and calculations tractable the shape of the earth is represented by the nearest simple geometric figure consistent with the desired accuracy For survey use sufficient accuracy is obtained with a the earth represented by an ellipse rotated about the earth s north south spin axis This 3D figure is called a spheroid or ellipsoid by some texts Geoid Historically surveying was done by optical means with heights being measured above sea level be using liquid bubbles to transfer levels from point to point The heights were therefore measurements above the equipotential surface of local mean sea level Considering the whole world and using sea level as a connecting da
42. e converted to BIL or BSEQ files by the AZEXHDF utility and input into any standard image processing package Coordinates output as listing during the AZGCORR run can be used to relate the images to maps Using the GeoTIFF output option in AZEXHDF produces a file containing image data and its registration coordinates this format is compatible with ERDAS and other image processing packages CASI none image items spectral enhanced spectral and ILS can be obtained on BIL or BSEQ format files and their related coordinates on separate files for use in user programs 3 9 Geocorrection in the real world The stated goal of azgcorr is to provide geocorrected images that may be overlaid on existing maps or GIS data It is important to understand the requirements for optimum correction to be achieved and to accept the limitations inherent in the problem and data As discussed elsewhere the main aspects of correction are geometric by using aircraft position and attitude and ground positioning by using DEMs with geoid spheroid corrections The third item not catered for in azgcorr is correction and adjustment of the pixel image radiometry The first two items along with user controls of view vector adjustment allow the image to be precisely matched with map or GIS data Note that it is not possible to achieve accurate matching without a DEM and geoid spheroid correction This is particularly the case in areas of high topographic change In relatively flat ar
43. e scans as well as details of pixel size and spacing In some scanner systems corrections also need to be applied to correct defects in the imaging lens For the sake of this discussion we are interested in the following main errors in these observations a timing error between navigation and scans b translational and rotational mismatch between navigation system axes and remote sensing instrument axes c errors in aircraft height above the ground and the local surface topography 5 12 1 timing adjustment Typically timing errors should not be present or have been eliminated prior to user data release Errors will show as uncorrected distortions on linear features where the aircraft attitude has been applied to the wrong place in the image Correction is made by using the ut parameter and steeping through small changes in time offset say up to 2 seconds initially the correction is quite sensitive so steps of 0 1 seconds is appropriate 5 12 2 attitude tilt adjustment These combined errors manifest themselves by the image being consistently misplaced or misaligned relative to map or vector GIS features Also pitch and roll errors will cause a scale error such that one part of the will be larger or smaller than the map features Corrections are made using parameter ua 5 12 3 scale adjustment Scale error becomes apparent when the above errors are reduced but the image is overall smaller or larger than map features This is adjusted
44. early in a project and upgrade the system appropriately In either case the minimum system configuration should be 32 Mbyte of RAM hardware floating point 2x the maximum image file size of free disc space a roll partition of at least twice the size of the RAM Processing speed is directly related to CPU floating point performance ie therefore CPU clock rate and disc access rates This minimum system will process data but with significant run times eg 10s of minutes per 1000 scans per band 4 5 Installing software Installation on Solaris or Linux only differ by the directories and search paths for default items It is assumed that the local directory usrMocal bin is available and may be accessed by users You will need the super user password a move the two programs either by network or CD to usr local bin directory cp YOUR_CD_OR_NETWORK_PATH az b If the programs have appended version numbers eg azgcorr 500 then rename them to just azgcorr mv azgcorr 500 azgcorr etc Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 16 20051015 Azimuth Systems User Guide AZGCORR c if there are geodetic correction files supplied eg sphsep grd these must be copied to the same directory as scanner data files or one used eg just for correction files and DEM files In the latter case the directory will need to be explicitly used as the path for the correction and DEM files Example user is Fred and has a def
45. eas moderate matching can be obtained with geoid spheroid correction Mosaicing of multiple overlapping lines can be done after each separate line is geocorrected with final matching by using view vector controls Again accurate matching will be difficult or impossible if a DEM has not been used In version 5 of azgcorr controls are provided for the use of regional DEMs which are available at various levels of quality for most of the world If nothing else is available these should be used if an attempt at precise georeferencing is desired Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 13 20051015 Azimuth Systems User Guide AZGCORR The third aspect mentioned above radiometry visually controls the overall pixel density levels across the image During post processing of remote sensing data it is usual to apply radiometric calibration sometimes misnamed as radiometric correction This ONLY adjusts the image pixel values to standardise values in radiometric units and allow for distortions noise or degradation of the instrument It is correctly described as at sensor radiometric calibration and does not allow for what happens to light between the sun the ground and the instrument Corrections applied to acquired images to allow for optical path are called Atmospheric Correction and are applied at Level 2 by such packages as ACORN FLAASH ENVI and 6S or ones based on MODTRAN Atmospheric corre
46. er Guide AZGCORR See section 5 12 for more details on using view vector controls option uaprh attitude corrections p r h corrections in signed degrees to be added to each navigation epoch attitude value Sense of corrections ve pitch raises the aircraft nose ve roll lowers the right wing and ve heading rotates the nose clockwise option uh z aircraft height correction z value in metres to add to every navigation epoch height AFTER datum shift and or map projection conversion option uo xyz 3D grid position correction x y z values in metres to be added to the aircraft coordinates AFTER datum shift and or map projection conversion option uow la Inz 3D geodetic position correction la In z values in signed decimal degrees la In and metres z to be added to the aircraft coordinates BEFORE datum shift and or map projection conversion option utt navigation to scan timing correction t value in decimal seconds to adjust navigation relative to the scans a negative value will appear to move an image feature backwards down the flight line option v verbose listing request Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 33 20051015 Azimuth Systems User Guide AZGCORR 7 1 introduction azexhdf allows the user to extract list or reformat selected data from an AZSPS HDF file Output files may be in one of several standard layouts and formats for transfer to image anal
47. erenced rectilinear output image corrected for aircraft position attitude and ground surface separation computed from aircraft spheroid height digital elevation data and geoid spheroid separation estimates Special processing is available for non image data eg CASI spectral and ILS corrected pixel coordinates are saved to allow positioning of pixels either on a map or scene image Navigation and image data input to azgcorr must have been processed or imported to an internal HDF file using the correct programs in the Azimuth Systems package to ensure that all data items are present and as expected The one exception is Level 2 data the basis of which is image data extracted from a Level 1B file with azexhdf massaged by a user program and input to azgcorr still in BIL or BSEQ format along with its originating Level 1B HDF file Navigation data on the internal HDF files is always geodetic latitude longitude spheroid height pitch roll heading and typically in GPS WGS84 datum The conversion to a local datum and map projection with or without DEM correction is performed just prior to image correction this allows for maximum flexibility It is important to note that all appropriate data items DEM etc must be on the same datum and projection This is discussed below Level 1B processing has two main functions for the raw image data instrument calibration and corrections have to be applied and the data converted to units of radiance
48. erred to the azgcorr support as resolving this may affect the local installation d message from azgcorr HDF internal error This may be due to the hdf file being damaged or the hdf file having the wrong permissions try Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 17 20051015 Azimuth Systems User Guide AZGCORR chmod rw your_file hdf if the problem persists contact support e azgcorr error message HDF file corrupt or wrong format Contact support 4 6 Practical aspects of running the program An optimum system with 1G RAM 3GHz CPU and lots of disc space running Linux 2 6 will process of the order of 1200 lines per second per band without a DEM and around half that with a DEM With the amount of data and calculation required correction of all bands for even a moderate sized site can take some time so the following details will help to avoid wasted time azgcorr run times will be extended by a increased number of bands b increased number of scan lines c reduced pixel size d presence of DEM and complexity of the topography ie more rugged more time e presence of other programs running on the CPU f amount of useable memory h shortage of disc space for output file azgcorr may run out of memory with an inappropriate combination of a too small pixel size and b diagonal flight line and c too small a roll partition on Sun or Linux The main points t
49. es HDF4 of release 4 2r1 Full details can be obtained from the main HDF web site http ndf ncsa uiuc edu The HDF format has considerable flexibility but only a basic subset has been used to create a file with a two level hierarchy Data items Vdatas which may have single values or vectors are grouped together to form Vgroups On the AZSPS implementation Vdatas have been used for all items which are limited to 1 dimension except main image data which is stored as a 3 dimensional SDS scientific Data Set item Every data item is identified by a name and this is used elsewhere in this document to refer to items These AZSPS HDF files can be accessed in user software using the appropriate HDF libraries NSCA provide utilities for viewing data item contents and items The AZEXHDF utility program is supplied which allows for general listings ascii files of multiplexed vector information and application specific files containing image data BIL BSEQ GeoTIFF and TIFF are cater for See section 7 below for the azexhdf user guide for more details Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 15 20051015 Azimuth Systems User Guide AZGCORR The HDF files used in azgcorr contain all the navigation and scanner image data as well as all the related metadata items for a site The following strategy has been adopted for AZSPS file contents a all post processed navigation and scanner image data is containe
50. eying and navigation positioning is done using the Navstar GPS system along with Glonass and shortly the EU Galileo constellation 3D positions can be obtained at up to 100 independent observations per second and using optimum equipment dynamic positional accuracies of a few centimetres can be obtained Static land surveying can be done easily down to a centimetre with higher accuracies possible but significantly more effort required as well as needing to take account of earth tides etc Relation between aircraft position and the ground The importance of the above details of soheroids geoid and datum are evident when correction aircraft acquired image data to match ground data or maps The aircraft position results in a 3D position and attitude latitude longitude height pitch roll and heading relative to the WGS84 spheroid With the ground surface shape known either in spheroid or geoid heights the image can be corrected to fit on a flat representation of the ground below the aircraft Reconciling gps positioning and traditionally derived maps As can be expected there is a problem relating positions obtained from GPS observations and those from traditional geodetic surveying There is no simple transformation to solve this to any degree of accuracy beyond a few metres at best a fudge is possible like the recommended OS procedure for GPS to National Grid For purely economic reasons the correct solution for a whole country will never be
51. f tiles is stored in the appropriate VG xy item after scaling Image data for squares may be in any order from the total image area the key may be ordered for best access or other reasons a SCpxyn SCpxy_sc ATimgxy CAimgxy CAsrcxy and CAilsxy are only used if the image is tiled b In none tiled files image items are stored as bands lines and pixels Typically Level 1 and 2 data is none tiled and Level 3 may be either 4 Derived image views Images resulting from level 3 processing are projected to a surface different from the acquisition surface the selected surface is indicated by the SCviewty flag with values 0 as source image is as original and not resampled 1 mean sea level of local datum 2 to a plane parallel with the mapping spheroid fixed GPS flight height 3 to observed flight height correction 4 digital elevation model DEM in local datum 5 DEM Geoid Spheroid correction navigation to mapping spheroids As discussed in detail elsewhere if the level 3 image is not SCviewty 4 or 5 then it WILL NOT be correctly registered on a map 5 Image Coordinates The position of a resampled and corrected image is defined by a set of coordinate values and increments With origin at pix 0 line 0 and using map projection grid coordinates SCposimag and SRCposimag values are 0 pixels 1 lines 2 x origin BL pixel 3 y origin BL pixel 4 xinc per pixel 5 yinc per pixel 6 xinc per line 7
52. file chunking option will minimise the disc space usual with diagonal flights areas of the image not written on are not stored d providing for same file support of different scanners eg Specim Eagle and Hawk even with different FOVs and pixel per scan This will allow simple access for full data cube display and analysis 1 1 2 A utility to provide pixel view vectors giving pixel positions instrument and sun vectors This will allow output to an external file or addition of the items to the Level 1 HDF file These items can then be used in 2 algorithms and atmospheric correction 1 1 3 an interactive version with a GUI is underway which will provide the same facilities as azgcorr but include interactive selection of parameters and viewing of meta data navigation and image input and results This will be a stand alone program and no third party packages are required It will initially be available for Linux systems but can be provided for MAC and MS windows if there is sufficient interest If users wish to make suggestions or have input into future developments they should contact Bill Mockridge at Azimuth Systems UK billm at globalnet dot co dot uk Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 4 20051015 Azimuth Systems User Guide AZGCORR 2 Summary of azgcorr functionality azgcorr combines multi spectral scanner image data and post processed navigation and produces a map projection ref
53. gation The method used in the azgcorr geocorrection procedures was in the passed called parametric geocorrection but of recent times has adopted the title direct georeferencing All this means is that the aircraft precise 3D navigation position pitch roll and heading is used for the geocorrection without the need for any ground control Azgcorr performs the final step in the production of map fitting remote sensing images As described below it contains many options for selecting mapping details and image definition and interpolation This allows it to cater for many types of scanner data and output images on all the main survey grade map projections azgcorr and support utilities are currently available for Solaris and x86 Linux Supported remote sensing instruments are ATM CASI Specim Eagle and Hawk and Hymap 1 1 Future developments Further developments under way and available during 2005 1 1 1 change internal files from HDF4 to HDF5 and HDF5 EOS this will provide identical functionality as HDF4 but has the added advantages of a supporting files sizes of greater than 2G essentially the file size is unlimited provided the operating system allows this b using HDF EOS structures for georeferenced images and having standard meta data allows the use of free display and analysis packages as well as commercial packages like ERDAS and ENVI In all cases no transfer file is required eg GeoTIFF saving disc space c the
54. gives a brief overview of the positioning requirements and associated errors inherent in airborne remote sensing and provides an understanding of the controls provided to minimise and adjust these errors To geolocate pixels of an image the following items or facsimiles are required a ECEF position of the instrument in the aircraft b ECEF attitude of the instrument c details of the instruments optics field of view pixels etc d timing information to link a b c The present standard approach is to use one or more integrated position and attitude navigation systems linked by timing pulses and messages to the required remote sensing instruments Positioning Suitable navigation instruments may be a combined gps position and attitude units or b gos and inertial or c gps position and attitude and inertial During the flight epochs of data are recorded that immediately provide or allow post flight processing to generate final positioning epochs consisting of at least time latitude longitude height roll pitch and heading Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 22 20051015 Azimuth Systems User Guide AZGCORR Scan timing Timing information is output from the gps that is used in the remote sensing instrument to allow the gps time of the scans to be recorded Remote sensing instrument optics details Geolocation needs the relation between the timed scans and the pixels forming th
55. hdf with a 5 metre square pixel size By default UK National grid coordinates will be used and all input bands will be processed Multiple command lines can be used IF allowed by the shell command line processor being used BUT must have command terminators between commands eg and of course make sense in the use of the program s One run of the azgcorr program processes the data from the input level 1 hdf file using the parameters supplied and creates a geocorrected image on the output level 3 file A second or subsequent runs with the same input and output files will OVERWRITE the previous results WITHOUT warning it does NOT apply a subsequent step in the process The program is controlled by a selection of command line parameters expects certain input files and generates program execution message output along with an output image data file The program has potentially long run times on old systems or if all bands are selected so running from a shell script that includes creating an output file compatible with an image processing package used for analysis makes for a convenient background or overnight batch run 4 2 Internal data files used by azgcorr It was decided from the start of the Azimuth Systems Scanner processing System AZSPS of which azgcorr is one program to use the NSCA HDF scientific file format This offered certain advantages of compatibility and access to basic file handling and data utilities AZSPS currently us
56. hods a cubic spline b linear and c nearest neighbor By default cubic spline is used resulting in a smooth image surface but will generate pixel values intermediate to adjacent ones which may have DN values not in the original image For uses such as classification nearest neighbor may be more appropriate as no new values are created Users are encouraged to try different methods to see how which best fits their application It is worth noting that linear and nearest neighbor are much faster than cubic If aircraft motion was extreme for any reason it is possible for the edge of particularly ATM images with their large field of view to open up This will be seen as black inlets encroaching into the image Parameter g gm gr can be used to control this gm is the size in pixels of a the minimum gap ie if a gap of greater than this occurs it will not be interpolated across gr is the count of pixels considered as a run of good pixels 5 10 BIL input of image data Image data may be extracted from a level 1b HDF file accessed by a user program to create an equivalent size and layout BIL file which is then input to azgcorr in place of the Level 1b data for geocorrection a run sequence to do this would be azexhdf bl 235 1 h a1 hdf Bs B a1raw bil userprogram Bs airaw bil stats Bin a1raw bil Bout a1new bil azgcorr 1 a1 hdf B 1 1 1 0 0 0 0 Bi a1new bil 3 a3 hdf The first azexhdf exports 3 bands in BIL layout to file a1raw
57. ift name MPdsvec F64 7 Datum shift vector for single point transformations MPimx0 F64 1 Image origin grid x MPimy0 F64 1 Image origin grid y MPtiles 132 1 number of tiles in image MPracs 132 1 MPcxy F64 var tile coordinates VGroup LEVEL 2 Contains details of user application level 2 processing Vgroup name LV2 Vgroup title Level2 Data itemprefix L2 Item name type maxv description L2desc C8 64 Vgroup description Level 2 user processed data Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 50 20051015 Azimuth Systems L2prog1 L2prog2 L2para1 L2para2 VGroup c8 c8 c8 c8 ATM User Guide AZGCORR 40 Vgroup 1st processing program 40 Vgroup 2nd processing program 128 User program parameter list1 128 User program parameter list2 Contains ATM scanner recording parameters and recorded calibrated or geometrically corrected image data stored as 16 bit integer to level 1b and either 16 bit integer or 32 bit floating for level 2 and level 3 Level 1 data is inserted by ATM_1 Data recorded with the DEI320 has 12 channels and from the AZ16 11 channels Note this is for pre 2001 data all ATM data from 2001 uses ATM2 below Vgroup name ATM Vgroup title ATM Data item prefix AT Item name type maxv description ATdesc C8 64 Vgroup description ATM scanner details calibration and data ATprog1 C8 40 Vgroup 1st processing program ATprog2 C8 40 Vgroup 2nd processing program
58. imits NAV navigation all related but post processed navigation linked to scanner data by gps time and scan number Sco scan coords final per scan coordinates corrected to scan nadir and transformed to the scanner MAP mapping datum and map projection details used to create a level 3 image LV2 level 2 level 2 details ATM ATM ATM data from original Daedalus system ATM2 ATM2 ATM data from AZ16 system CAS CASI CASI or other ccd scanner data Navigation vector items are stored compressed using a simple multiplier which is also stored in the HDF file This saves disc space without loss of precision Image items are stored as unsigned integers again scaled to best preserve precision Optionally image items may be stored as floating point but file sizes will be doubled Using unix utilities HDF files may be copied moved or archived but NOT viewed edited concatenated or truncated Data items are described by name data type maximum number of occurrences of the type and a brief description Notes specific to a Vgroup appear after the items description for that VGroup and general notes appear at the end of the document VGroup PROCESSING Contains details of the file processing level creation and authorship Vgroup is created by SITEINIT with PRIevel updated by appropriate programs Vgroup name PRO Vgroup title Processing Data item prefix PR Item name type maxv description PRdesc C8 64 Vgroup description Latest processing level of fi
59. ion file name ATcaltab F32 var calibration values table ATgains F32 var gains ATradsc F32 var Channel radiance scaling multiplier ATrunits C8 32 Radiance units ATimgmin F32 var Channels minimum values excluding zero ATimgmax F32 var Channels maximum values excluding overflows ATimgzer 132 var Channels no of zero values ATimgovr 132 var Channels no of overflowed values SCimtype C8 32 Image type source or resampled 0 fill SCorder C8 32 Pixel in scan order Left gt Right or Right gt Left direction of lines increasing SClndir C8 32 Scan line direction flight direction or north up SCtiles C8 32 Tiles in image not tiled single image or number of tiles SCbands 132 1 Bands in image SCpixels 132 1 Pixels in image SClines 132 1 Lines in image SCpixfmt C8 1 Pixel format 8bit unsigned 16bit unsigned SCHDFfmt 132 1 Pixel HDF number format flag see HDF documentation for details SCimover F32 1 flag value indicating overflowed values see general note 2 SCimunder F32 1 flag value indicating underflowed or missing values see gen note 2 SCpixbytes 132 1 Bytes per pixel SCposn C8 32 Position data relation posns per scan posns per image SCaxes C8 32 Coordinate axes for position along flt dir N up SCxypix C8 32 relation of coordinates to pixel centre BL SCpixwid F32 1 Pixel width x or scan direction metres SCpixhgt F32 1 Pixel height y or flight direction metres SCviewty C8 32 Image view type see general note 4 SCvpl
60. ise angle from grid N option pab Output pixel coordinate alignment If this option is present pixel coordinate limits are aligned at bottom left SW corner If this option is not present coordinate limits are aligned at the centre of pixels NB1 aligning at bottom left implies final image limits are to the outside edge of the peripheral pixels NB2 CASI spectral enhanced spectral and ILS coords are always returned pixel centered option r rv Coordinate rounding rv coordinate rounding value def is pixel size rounding is to multiples of rv option ro xm ym xx yx Enforced output limits Output image enforced x y limits grid coords allows different data sets to be matched NB wrong values may extend the image and cause runtime memory problems and large file size h Aircraft height control option h ht Constant height ht aircraft height above ground option hn Navigation height used Selects the use of GPS navigation height This is the default if no h is used option hs sc Navigation height with correction Same as hn but allows a user constant height correction to be made sc height correction to be added to aircraft hgt Requirement options hn or hs MUST be used with DEM and geoid spheroid correction option hsu Geoid spheroid height correction Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 29 20051015 Azimuth Systems User Guide AZGCORR height correction fo
61. ives 256 option Cx fp create binary file with CASI spectral and ILS fp file path for created file file contents for each image pixel 0 pixels and each image line 0 lines coordinates are pairs of xy s grid coords format is tenths of metres in signed long NB must be run separately from BIL p may be used option Cr fp as for Cx but coords are col row pairs to match the row column pairs match the SRC image format is uint16 NB must be run separately from BIL p may be used option T fp convert any level image data to TIFF file tif option G fp convert level 3 image data to GeoTIFF file tif fp file path for created file 1 these files are TIFF level 6 0 or GeoTIFF 1 1 4 pixels are band interleaved by pixel BIP and there are the requested no of bands samples per pixel in 16 bit unsigned 2 Note that some readers may not allow more than 3 bands 3 Only TM UTM UKNG projections are supported in this version option d dn image data item name if not default default is to use the standard item for ATM and CASI option S fp convert image data and output to Sun raster file fp file path for created file option c rgb band nos for colour image Sun raster file option m c band no for monochrome image Sun raster file option p pO pn l0 In image patch limits pixels and lines pO pn pixel limits in the range 0 to number pixels in the image l0In scan line limits in the range 0 to lines in image This can be used for Sunraster B
62. l items NB max of 12 items NB this is for VData items only NOT SDS image items vi st en vector index limits to save file Start and end index 0 gt to save from HDF VData items to file vq fmt format for qual vectors items C format description for navigation qual item listings default is 08Ix VS add scan number in col 0 of multiplexed output This is to be used with NVscnum and NVscsecs only vp n0 n1 1 user supplied list of decimal places no of decimal places in order of vector vn items This is to control output listing of a set of multiplexed vectors Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 36 20051015 Azimuth Systems User Guide AZGCORR if only nO is given this will apply to all items defaults dps are v lt 90 5 else 5 except lat and Ing are 7 dps option vm ALL requested vectors to be output multiplexed NB vectors must be from the same Vgroup and of equal length eg pitch roll and heading Notes 1 Filenames can be complete paths 2 Vgroup and data item names are case sensitive 3 Band numbers are 1 relative 4 Pixel and line patch limits are zero relative 5 for version 2 0 0 onwards local libraries for TIFF and GeoTIFF are not required Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 37 20051015 Azimuth Systems User Guide AZGCORR 7 azexhdf data export utility 7 1 HDF file contents listing
63. le PRlevel C8 8 Latest processing level of file Prcdate C8 32 File creation date PRhostn C8 64 Host name of creating workstation PRhostid C8 16 Host ID of creating workstation PRsoftware C8 64 Processing software copyright notice VGroup MISSION Contains all pre flight operations and target delimiting values Site limits may be either or both of time and scan and are inserted by SITEINIT CASI details are inserted by CASCHK and are obtained from an analysis of the complete CASI data file or files Vgroup name MIS Vgroup title Mission Data item prefix MI Item name type maxv description Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 47 20051015 Azimuth Systems User Guide AZGCORR Midesc C8 64 Vgroup description Mission and site details from flight logs Mlprog1 C8 40 Vgroup 1st processing program name Mlprog2 C8 40 Vgroup 2nd processing program name Mlcopyw C8 64 Data copyright notice Mlairc C8 32 Aircraft name Mipilot C8 32 Pilot name Minavig C8 32 Navigator name Mloper C8 32 Operator name Mlbase C8 32 Sortie base Midate C8 16 Flight date Mifltno C8 32 Flight number Mlprojco C8 64 Project code Mipiaff C8 64 Principal investigator and affiliation Mitarget C8 64 Target name Mifline C8 32 Requestor s flight line name number Mlaspeed C8 32 Airspeed Mitrack C8 32 Track Mlalt C8 32 Altitude Mlweath C8 128 Weather Mlicloud C8 32 cloud cover Miland C8 32 land type and amount
64. le path fn BSEQ input file Default none Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 25 20051015 Azimuth Systems User Guide AZGCORR d Geodetic datum shift details For details of commonly used data shift values see Appendix A option ANO No datum shift performed This is provided for use ONLY with mTM full parameter set below and indicates to the program that no datum shift is be performed as navigation data remains in WGS84 throughout processing option d95 OS 1995 datum shift method applied Ordnance Survey 95 method using GRS80 datum See Ordnance Survey publication National Grid ETRF89 Transformation Parameters Geodetic Information Paper No 2 2 95 V1 2 This is the default if no d option is used option dDUTCH for Netherlands National Grid No parameters option d7 sc a p2 dx dy dz rx ry rz sc 7 parameter Bursa Wolff shift Applies a 7 parameter Bursa Wolff single point transformation sc spheroid code 1 if a and p2 are supplied O Int Hayford 1950 1 Airy 1830 UKNG a semi major axis p2 semi minor axis or reciprocal flattening or eccentricity metres dx y Z origin shift in metres rx y z axis rotations in secs sc scale excess in ppm ie scale 1 Sc 1000000 There are no numeric defaults except as mentioned m Map projection details For details of map projection and required parameters see Appendix B If m is not supplied the built in c
65. n and basic run requirements azgcorr help will give an uptodate concise description of all parameters 5 2 basic correction azgcorr p 55 1 a1 hdf 3 a3 hdf ex1 Image level 1 input is from a1 hdf desired pixel size is 5 metres square and image output will be on a3 hdf Important defaults which would be applied are map projection would be UK National Grid 1995 version and all input bands would be corrected image would use bicubic interpolation To limit the number of bands azgcorr p 5 5 bl 5 3 2 1 1 al hdf 3 a3 hdfex2 would give 3 ATM bands suitable for a pseudo RGB image these would be in R G B order on the a3 hdf file 5 3 changing the map projection no datum shift required azgcorr mUK99 osgb99 rest as ex2 ex3 Now the 1999 version of the UK National grid will be used projection correction values will be from file uk99orid Other projections not requiring specific datum shifts are Dutch and New Zealand the shift from WGS84 is built in to the conversion 5 4 changing the datum shift and map projection This will be required in the cases where the desired map projection does not include an integral shift the majority or an accurate local shift is being used Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 19 20051015 Azimuth Systems User Guide AZGCORR azgcorr d7 0 113 7 57 1 98 4 0 05 0 18 1 7 1 28 mTM 0 0 0 7 0 9996 0 500000 then as for ex2ex4 Here the Transverse
66. nated 132 INT32 32 bit signed integers sl32 INT32 32 bit integers containing scaled floating point values UI32 UINT32 32 bit unsigned integer F32 FLOAT32 32 bit floating point F64 FLOAT64 64 bit floating point SDS see below format indicated by SCHDFfmt may be UINT16 or FLOAT32 Item dimensions marked as variable var or SDS may be of any length Variable and SDS items only appear in VGroups if they have 1 or more values 2 Image items On all AZSPS file levels image items are stored as HDF SDS Scientific Data Sets The layout and dimensions have been chosen so that the line dimension is variable Data is stored in the SDS items with the following convention Level 1 pixel order is as recorded by the instrument eg for the ATM pixel 0 is on the port side of the flight path Line order is as recorded in flight direction Band order is from 1 to however many bands Level 3 If the image is created as a north up one then it is ordered for quadrant 1 ie pixels increase as x increases left to right lines increase as y increases from south to north of image If head up image creation was selected then the images axes are x across the flight direction increasing left to right with pixel O on the left y is in flight direction increasing bottom to top of image line 0 is at the bottom Level 3 images outside the flight line area are zero filled Note that azexhdf has options to create output files ordered to suit other conventions
67. nd other parameters are used to create a particular format of DEM of which there are many dozens Merging different DEMs used for georeferencing When several DEMs are merged and used to georeference an image the DEM s geolocation must be the same as the mapping parameters used for the final image data This may mean the different resolution DEMs need different transforms projection and interpolation this is provided by the azgcorr controls 3 4 3 DEMs handling controls in azgcorr Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 10 20051015 Azimuth Systems User Guide AZGCORR From version 5 of azgcorr the following controls are provided to merge and use DEMs a read and decode several standard formats SRTM 1 SRTM 3 GTOPO32 GeoTIFF flat files various ENVI BIL b geographic DEMs can be datum shifted and map projected using the same parameters as for the image data and interpolated to a regular grid c gridded DEMs provided on a map projection not suitable for the image data mapping can be re projected to a different map projection this done by reverse transform re projection and re interpolation d LIDAR point clouds can be used to form DEMs there are two basic methods provided depending if the data is time ordered or xy sorted It does not provide survey line to line leveling this is assumed to have been done or to be ignored e low resolution DEMs can be re interpolated to be used fo
68. nds on the concise version obtained in the standard unix usage method obtained by typing azgcorr help It should be noted that the most up to date information is from the usage version Notes on the description below a Letters preceded by minus signs are the parameter names as summarised in the Usage listing b Filenames always implies full unix paths c Command line parameters and values may be in any order d Latitude and longitude values in signed decimal degrees are ve for south and west e All units of distance are in metres f Option requirement in typical runs are optional unless stated option 1 fn level 1 HDF file path fn input Level 1 HDF file path requirement MANDATORY default NONE option 3 fn level 3 HDF file path fn output Level 3 HDF file requirement MANDATORY default NONE option p dx dy Output pixel size Output pixel x y sizes in metres Requirement MANDATORY default NONE option B btsof BIL or BSEQ file content details b total bands on file t number type on file O uint16 1 float32 S scale o offset to convert B file values for geom correction and saving as uinti6 v p s o f fill value for bad pixels good pixels are lt f if f O the default values of O and Oxffff uint16 or 10e30 float32 are assumed requirement MUST be used if Bi or Bs are used defaults b NONE s 1 0 0 0 0 option Bi fn BIL file path fn BIL input file Default none option Bs fn BSEQ fi
69. ne positioning ILS same number of bands as image for single pixel Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 12 20051015 Azimuth Systems User Guide AZGCORR ENHANCED image many bands of continuous pixels but of restricted image width SPECTRAL SRC single band continuous pixel image for scene positioning ILS same number of bands as image for single pixel Using the appropriate options AZGCORR processes these items as follows spatial image spectral SRC enhanced spectral SRC and enhanced spectral image handled as ATM ie continuous image all three methods of interpolation may be used and a rectilinear interpolated image results spectral image enhanced spectral image and ILS geometrically corrected grid coordinates are calculated for each pixel and saved on the HDF file to allow positioning over the SRC image Note that the data items will also be copied to the level 3 file Coordinates are saved in vectors CAimgxy for image pixels and CAilsxy for the ILS pixel Note that ONLY selected lines and bands are transferred to the level 3 file spectral image a special option cspi allows spectral data to be processed as though it was a continuous touching pixels space between pixels is filled by the selected interpolation method Note that interpolation option has no affect on the pixel coordinates calculated for none image items 3 8 Viewing the results Interpolated image items can b
70. o explains why if there is no DEM and the corrected image is projected to sea level when there is topography at say 500 metres then the pixels will be 500 metres misplaced To further complicated matters the datum used to measure heights from may be the surface of either the local spheroid or the local geoid As discussed in section 3 2 the spheroid is an ellipse rotated about the earth N S axis that is a best fit to the earth s general shape this is to make navigation maths tractable The geoid is in essence mean sea level as it appears in the free ocean and how it would appear ina bole hole connected to the ocean Sea level is affected by local gravity effects and is higher in thick parts of the crust and lower in thin parts When elevation measurements are made by optical surveying from a fixed sea level marker using leveling the heights are measured above the local geoid When heights are measured using satellite surveying gps assuming no corrections are made in the gps the heights are above the spheroid In general and assuming no transformations have been made DEMs obtained by land surveying and traditional photogrammetry using non gps ground control will give geoid heights DEMs obtained using LIDAR or recent photogrammetry using gps ground control will give spheroid heights The transformation from relative to spheroid to relative to geoid is called geoid spheroid correction Correction values are measured by analysis of satelli
71. o note when running azgcorr is its potentially long run time Users are advised until they obtain a feel for these times to restrict the number of bands selected for correction and to use an output pixel size no smaller than 5 metres run times are several times longer if a DEM is present Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 18 20051015 Azimuth Systems User Guide AZGCORR 5 Using azgcorr This section describes how to achieve desired results using the various control parameters Throughout the section for clarity on local file paths will be given the user may use full paths for any file in their place There are no defined file naming requirements but we tend to use hdf as the HDF file extensions a for ATM data and c for CASI ccd scanner data To avoid confusion the level 1 data considered in examples below is assumed to have navigation all on WGS84 The program may only used for the period and on the system or systems it is licensed for if any of these criteria are not met an error message will appear and the program will terminate In the examples below each line starting with azgcorr is used as one unix command line either to be typed in or as one line of a batch file The ex at the end of each line is the line s example number for reference purpose and is to be LEFT OFF the command line 5 1 to obtain online program help azgcorr with no parameters will show the program versio
72. on 6 under u and new HDF items are described in general note 7 Appendix D Internal changes Version 5 has undergone a major internal change to switch from a mixture of floating point precisions to the use of double precision for all navigation and interpolation calculations This is transparent to the user but may result in longer run times on older computer systems but faster times on the latest 64 bit hardware There will also be increase in memory usage The main reason for the change is to pave the way for processing of very large images of high resolution as well as to simplify calculations by avoiding having to change back and forth between single and double precision to save memory HDF version has been moved forward to HDF4 2r1 which solved some incompatibilities with GeoTIFF and JPEG libraries Linux version A full Linux version is now available which runs with most recent x86 releases distributions and hardware see section 4 4 and 4 5 for full details User Guide alterations The following sections of this User Guide have been altered or added 1 Future developments 3 4 Digital Elevation models re write Describes the use of multiple DEMs to allow the overlaying of a regional DEM with a detailed local one allows the composited DEM to be saved for further use 3 9 Geocorrection in the real world new Discusses the effects of radiometric calibration atmospheric correction and use of DEMs to achieve optimum geocorre
73. onversion method UK National Grid 1995 is used option mUKNG TM set to UK National Grid This uses the Airy 1936 spheroid and has no built in soheroid geoid correction and requires a seven parameter datum shift to be applied see d7 above option mUK99 fp TM set to UK Nation Grid 1999 method fp file path to OSGB99 correction file The details of this method using OS supplied correction grids OSTN97 and OSGM91 are described in OS publication User Guide v1 2 12 1999 option mUK0O2 fp TM set to UK National Grid 2002 method fp file path to OSGBO2 correction file Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 26 20051015 Azimuth Systems User Guide AZGCORR This method is similar to the 1999 one but uses an iterative reverse conversion and a correction grid described are being more accurate The grids released by the OS had been cut to about 10Km offshore around coasts The grid supplied for use in azgcorr has been filled in these offshore areas by adjusted values from the 1999 method option mIRNG TM set to Irish National Grid As of azgcorr version 4 0 0 the latest 02 2003 accurate conversion method for Ireland has not been included contact Azimuth Systems for further information options for Transverse Mercator projection Several parameters sets are provided for using the Transverse Mercator projection in addition to the special cases for the UK and Irish national grids above
74. ows ATimgzer 132 var Channels no of zero values ATimgovr 132 var Channels no of overflowed values SCimtype 132 1 Image type flag O as source 1 resampled SCorder 132 1 Pixel order flag O I to r 1 r to in direction of lines increasing SClndir 132 1 Scan line direction flag O flight direction 1 north up SCtiles 132 1 Tiles in image 0 not tiled single image gt 0 number of tiles SCbands 132 1 Bands in image SCpixels 132 1 Pixels in image SClines 132 1 Lines in image SCpixfmt 132 1 Pixel format flag O 8 bit unsigned 1 16 bit unsigned SCHDFfmt 132 1 Pixel HDF number format flag see HDF documentation for details SCimover F32 1 flag value indicating overflowed values see general note 2 SCimunder F32 1 flag value indicating underflowed or missing values see gen note 2 SCpixbytes 132 1 Bytes per pixel SCposn 132 1 Position data relation flag 0 posns per scan 1 posns per image Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 51 20051015 Azimuth Systems User Guide AZGCORR SCaxes 132 1 Coordinate axes for position flag O along fit dir 1 N up SCxypix 132 1 relation of coordinates to pixel flag O centre 1 BL SCpixwid F32 1 Pixel width x or scan direction metres SCpixhgt F32 1 Pixel height y or flight direction metres SCviewty 132 1 Image view type flag see general note 4 SCvplane 132 1 Image view y plane position metres SCposimag F64 var Image position coordin
75. performed ie re observe all original ground points by GPS and recompile all maps To summarise for our use of GPS for remote sensing aircraft surveying a surveying and platform positioning is by GPS which gives an observation a 3D position b relating dynamic and static observations using GPS is easy to a few tens of centimetres c relating these observations to existing maps requires various adjustments the first of which is the transformation of the aircraft position on the GPS datum to the local mapping datum moderate accuracy few metres is done using an observed data fudge d more accuracy requires field GPS observation of control points The default method used in azgcorr for the UK is to transform from GPS satellite datum WGS84 to UK National Grid uses the Ordinance Survey recommended National Grid ETRF89 Transformation Parameters 2 1995 ver 1 2 claimed to be accurate to the 2 metre level Asecond method available from azgcorr version 4 4 0 Jan 2003 uses the release of the OS correction grids and interpolation methods OSTN97 and OSGM91 provided as option UK99 described in the OS User Guide v1 2 1999 For use in azgcorr this involves a large 5 Mbyte external correction file so it is not set as the default UK95 covering UK only will remain the default if no other method is selected For areas outside UK appropriate map projections are provided for some local countries which may also include nationally defined datum transfo
76. ptic axis nadir pixel n or n 5 ie 230 or 225 5 but not 124 3 p port pixel O pixel 1 is on the port side 1 max pixel is on the port side fv lens field of view in decimal degrees option ccd o p fv pfv tp general ccd details to replace file defaults o optic axis nadir pixel decimal p port pixel O pixel 1 1 max pixel fv lens field of view in degrees pfv field of view port pixel to optic axis tp total pixels in field of view option cca pt load casi ccd pixel view angle table from external file Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 30 20051015 Azimuth Systems User Guide AZGCORR pt file path name for pixel view angle table Note this table is usually added to the HDF file in post flight processing so the use of the parameter should not usually be needed Angles are from port to starboard in flight direction in decimal degs and must equal in number the current viewed full ccd pixels for all processing see general note 6 Appendix D Lee Output image interpolation control option ic sm Bi cubic Method uses a cubic tensioned spline sm is the spline tension This is the default if i is not used sm smoothing value 0 001 50 0 def 1 0 0 001 is very smooth 50 is linear interp option il linear option in Nearest neighbour option il2 second pass interp is linear option in2 second pass interp is nearest neighbour option ic2 sm second p
77. r WGS84 geoid spheroid applied as a constant based on map centre option I sten Input scan lines to process option Is sts ens Scan line numbers to limit processing st and en are scan counts in the image from 0 and sts ens are original instrument allocated scan numbers in the range of items CAsscan CAescan CASI vgroup or ATsscan ATescan ATM vgroup Default with I or Is missing is to process all scans on the input file b Input bands to process option bl b1 b2 1 List of input bands to process option br b1 bn Inclusive band range to process Note that if less than the total bands are processed output bands may be reordered For example with b 532 1 the output image bands will be 1 input band 5 2 input band 3 etc Default with no b option is to process all input bands Cis CASI processing options option call process all present data in default modes option cspa DO NOT process IMG if spatial def process option cils process ILS def do not process option csrc process SRC def do not process option cspe process spectral def do not process option cspi process spectral as complete image option cspw process enhanced spectral at minimum width default ie not equal in size to SRC image Default for ILS and spectral is to save pixel coords as extra bands and apply no image interpolation option cc o p fv CASI ccd and lens details CASI ccd lens details to replace program defaults oO o
78. r in fill on high resolution ones several methods of interpolation are provided used for both geographic and gridded data and all allow for gaps in the data f DEMs can have geoid spheroid correction added or removed corrections are calculated from the whole world EGM96 coefficient grid g any number of DEM tiles may be merged h all DEMs may have holes which will be processed as follows on individual file input interpolation will work on row cols on runs of good data nodes until a set of no data nodes is reached if the set of no data nodes is greater than a user control parameter eg 4 in a row then only the good data run is interpolated and the no data run preserved in the merged DEM interpolation starts again after the gap after all input DEMs of all levels have been merged a final pass will look at remaining gaps they will be filled in if they are smaller than a user control parameter eg 2x2 or 3x3 i The merged DEM can be saved for reuse several save formats are provided j to allow viewing in image display programs it is possible to have the valid elevation values offset so that for example missing data is zero 0 which display as black and sea level starts at 100 when reused in azgcorr this offset is allowed for Merge sequence Several overlapping DEMs to be composited to form a combined DEM covering the image area are processed in the order of increasing resolution so global regional local At each level of
79. required controlling output image interpolation BIL input of image data typical complete run user controls for view vector adjustment azgcorr run options and parameters azexhdf data export utility 7 1 introduction 7 2 basic use 7 3 options and parameters 7 4 applications of azexhdf A Commonly used Datum Shift and Spheroid values B Map projections and required parameters C BIL file and BIL STATS file details D AZSPS Level 1 and Level 3 HDF file details Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 1 20051015 Azimuth Systems User Guide AZGCORR New items and updates in version 5 0 0 This section summarises major changes in this release of the programs Future minor changes indicated by incrementing of the third version digit are described in release notes that are available with updates DEM handling Major improvements and controls provided for the handling of digital elevation models DEMs discussed in detail in section 3 4 below This is compulsory reading as the use of some parameters has changed which may require a change to existing batch files View vector control A new set of controls have been provide to allow users to fine tune the geocorrection to remove final view vector instrument pointing errors and thus to adjust images to fit maps or vector GIS data to the pixel level Use of these controls is covered in section 5 12 below parameters are detailed in secti
80. rmations eg Netherlands and Belgium 3 3 Map projections The default procedure for UK outlined above does a one step conversion from WGS lat long height to UK national Grid map projection coordinates The more usual method of transformation does this in two steps allowing more flexibility Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 7 20051015 Azimuth Systems User Guide AZGCORR First the GPS position latitude longitude and spheroid height on satellite datum WGS84 is transformed to a local datum lat long height Then the geographic spheroidal coordinates are transformed to a suitable rectilinear coordinate set using a map projection Representing points ona spheroid by points on a flat surface is at best a compromise For survey use only a few map projections have the required characteristics of accuracy and scale and direction representation these are Transverse Mercator eg UTM UK National Grid etc Lambert Conical Orthomorphic Universal Polar Stereographic above 80 degs north or south a b c d other local specially designed ones eg Dutch New Zealand n Other projections included are Mercator Oblique Mercator and Rectified Skew Mercator Each of these projections has a set of defining parameters usually agreed on a national scale azgcorr allows the selection of these projections and parameters details are described below Remote Sensing Scanner Processing Sys
81. roid So they need transforming to the map projection to be used for mapping image data and interpolating to a regular xy grid Regional Regional DEMs may have been produced by several means that have limited resolution say down to 5m but also tend to have higher vertical errors than the local ones below Typical examples of these are the Nextmap DEMs of UK Local non Lidar Local non Lidar DEMs are from originally optically surfaced heights and control points and in filled from photogrammetry from film aerial photography Another source is gridded contour data Heights are above geoid and resolution may be down to 2 5 metres heighting errors are 5 25 cm Local Lidar These are using high resolution perhaps even down to 1 meter grids and generated from LIDAR data Final DEM quality will vary according to the effort put into processing from the raw flight data to the DEM Usually DEM heights are spheroid ones DEM format and positioning details There are may layouts formats and positioning methods used for DEMs The important details to note are grid type may be geographic or map projection or LIDAR point clouds format may be ascii fixed or free format or binary either may be compressed or not positioning geolocation details may be centre of a grid cell or one corner order may be in rows or columns from N S S N W E or E W geolocation geographic or grid coordinates of a given projection Various combination of these a
82. s displayed as item MPproj in the Mapping Vgroup MP of an azexhdf listing 1 initialises TM using WGS84 with central meridian cm References SNYD Map Projections A Working Manual J P Snyder USGS Professional Paper 1395 1987 Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 44 20051015 Azimuth Systems User Guide AZGCORR Appendix C BIL file and BIL STATS file details The standard flat file format used for remote sensing data is Band Interleaved by Line BIL For historic reasons this has no header to describe the file contents nor data value format azgcorr can also generate similar files in Band Interleaved by Pixel BIP and Band Sequential BSEQ but these are used less often azexhdf can generate BIL files and an associated AZSPS file that contains in readable text a description of the BIL file contents This description file follows no standard as there is none but may be used and adapted for user purposes There is also an option to output a per band histogram to this file See azexhdf running instructions for how to create the files BIL format means that for each scan line all pixels in sequential order across the scan appear in band order for the scan ie line O band0O pixel 0 pixel n band 1 pixel O pixel n band m pixel 0 pixel n line 1 band0O pixel 0O pixel n etc BIL files output by azexhdf have no pack bytes at any place in a band or line If the AZSPS header informa
83. space aligned at a fixed spheroid height usually zero It may only approximately match a map in that projection as a map is in essence a 2D representation of the surface of the geoid plus the topography Level 3B processing uses digital elevation model DEM data as well as other calibration values ground control points GCPs to achieve precise location that will be optimum for the navigation DEMs and control Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 5 20051015 Azimuth Systems User Guide AZGCORR 3 Geocorrection concepts used in azgcorr 3 1 Goals for correction Stated simply the purpose of the program is to produce an output image which overlays an existing map The rotating mirror ATM Hymap or push broom CASI Specim or other scanners have positions calculated for every pixel and then the image is interpolated to a rectilinear grid which may be projected to a plane relative to the aircraft or related to existing topographic data In azgcorr it is important to note that this ground referencing is only achieved by using observed scanner aircraft position and attitude and referencing scan positioning to elevation DEMs information Ground control points are ONLY used for calibrating DEMs and geoid spheroid separation data In all the following discussion it should be noted that the navigation attitude used HAS to be that attitude experienced by the scan head If a gps attitude unit is use
84. stcols 256 hbnd 1 hzer 0 hovf 0 hcol 0000000000 etc for rest of 1 band histogram The level 3 file from the same data set is scanner AZ16 item ATdata proclevel 3 bfile a3 bil pixels 2190 bands 1 lines 393 pixfmt 0 radscale 1 00 pixby 2 bandby 4380 band 1 obnd 1 min 24662 max 32310 xys 259176 0 291036 0 3 000 0 000 0 000 3 000 histcols 256 hbnd 1 hzer 148652 hovf 0 hcol E A followed by 1 band histogram Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 46 20051015 Azimuth Systems User Guide AZGCORR Appendix D AZSPS Level 1 and Level 3 HDF file details The HDF layout used for the Azimuth Systems scanner processing system AZSPS is described below A restricted subset of HDF interfaces has been used All data items are only identified and accessed by name A two level item hierarchy is used VDatas in single level VGroups Data items are only stored as single dimension VDatas with one or more values or three dimensional scientific data sets SDS linked to particular VGroups Data items can be read using general released HDF utilities or the supplied utility azexhdf HDF used in this release is HDF4 2r1 Some items are application related and the user is referred where relevant to the appropriate processing program VGroups and contents Mnemonic name contents PRO processing details of the system used to create the file MIS mission descriptive details of the flight site and site time and scan l
85. te orbits and are available from a USGS NASA agency Values vary over the earth s surface in the range 50 to 100 metres From the discussion on height errors to image positioning it is clear that these corrections are very important for the final result Geoid spheroid transformations are typically applied to DEMs generated by national mapping agencies so they match existing maps 3 4 2 DEM types and details Global There are several global DEMs available with e best known being the SRTM ones and GTOPO30 Both are low resolution and were generated for use by cruse missiles so original quality was less than Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 9 20051015 Azimuth Systems User Guide AZGCORR optimum for scientific users Resolution is 1 or 3 second for SRTM and 30 second for GTOPO30 The DEM s surface representation quality varies due to the varies data sources used for GTOPO and to radar reflection problems with SRTM The latest 2005 final processed SRTM has had a lot of work done to improve missing parts but both data sources need reviewing before using in a georeferencing project This is best done by creating a viewable image SRTM 3 is generally available for N America SRTM S for the rest of the world and only between 60S and 60N GTOPO30 is available up to about 84 N S Both of these DEMs are available as geographic grids based on EGM96 ie WGS84 datum and are measurements above the sphe
86. tem c Azimuth Systems 1996 2005 Version 3 00 8 20051015 Azimuth Systems User Guide AZGCORR 3 4 Digital Elevation Models DEMs 3 4 1 introduction As explained above a remote sensing image is formed by light reflected from the ground surface or top of the vegetation cover Different points on the ground and canopy will be at different levels in mountainous terrain the differences may 100 s of metres from pixel to pixel It follows that to correct this image so that it will overlay a map not only is the aircraft position and attitude be needed but also a suitably accurate representation of the reflecting surface This is available as a grid of numeric values of heights above some standard level or datum a so called DEM Digital Elevation Model or DSM Digital Surface Model When heights where only available by optical surveying it was only possible to get ground heights with the advent of methods to measure DEMs from aircraft or satellites then the elevation may or may not allow for the vegetation canopy For correcting optical airborne remote sensing data it is usual to have the canopy included so the DEM is the height of the ground or canopy whichever is the highest above the datum To give an idea of the importance of DEM accuracy on final pixel positioning from simple trig if the angle to the pixel is 45 degrees form the vertical through the aircraft then the error along the ground will be equal to the error in the height This als
87. tems NVscnum and NVscsecs link scanner scan lines with the geolocation navigation NVscsecs is the gps time of the scan number in the same index entry of NVscnum Geographic location of a scan is then calculated by interpolation using gps time VGroup SCAN COORDINATES Contains post processed and interpolated navigation on a per scan basis This is the Level 1B geolocation data on a one location point per scan basis Common indexed entries in the CO vectors give the location data for the same index entry for the line dimension in the image data SDS VGroup name SCO Vgroup title Scan coordinates Data item prefix CO Item name type maxv description COdesc C8 64 Vgroup description Navigation data interpolated to scan times COprog1 C8 40 Vgroup 1st processing program COprog2 C8 40 Vgroup 2nd processing program COoffs 132 1 Offset code for scanner in aircraft COstime 132 1 Time of site start dec secs Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 49 20051015 Azimuth Systems User Guide AZGCORR COetime 132 1 Time of site end dec secs COsscan 132 1 Scan number of site start COescan 132 1 Scan number of site end COscans 132 1 Total scans with navigation COscint 132 1 Interval of scan number for scans with navigation COtime sl32 var Time GPS dec secs COutc sl32 var Time UTC dec secs COlat sl32 var Latitude dec degs COlng sl32 var Longitude dec degs COhgt sl32 var Spheroid height
88. tion file is requested it consists of a set of name and value pairs separated by spaces describing the contents and layout of the BIL file these are scanner AZ16 CASI etc item name of image item from HDF file Atdata CAimage etc proclevel 1 2 or 3 bfile the BIL file being described pixels p bands b lines p b and are integer total for each dimension output pixfmt 0 UINt16 and 1 4 byte float radscale 1 00 means unscaled pixby bytes per pixel bandby total bytes for a complete band band b obnd ob min m max x repeated for each band in its output order b is from 1 to bands output ob is the original band number min and max are the band DN limits excluding 0 and overflow values xys for a level 3 file this is the SCposimag vector items 2 to 7 see HDF description general note 5 If a histogram was requested the following is present histcols n n is the number of columns in each histogram then the following are repeated for each band output hbnd b hzer z hovf o hcol b is band output z is O column entry and o the overflow entries then histogram columns 10 per line A typical level 1 file would be scanner AZ16 item ATdata proclevel 1 bfile a1 bil pixels 718 bands 1 lines 5167 Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 45 20051015 Azimuth Systems User Guide AZGCORR pixfmt 0 radscale 1 00 pixby 2 bandby 1436 band 1 obnd 1 min 24531 max 24887 hi
89. tractable for distance and area calculations Used for many local coordinate systems eg UK and Irish national grid Also appears as Universal Transverse Mercator or UTM defined in 1947 by USGS US Army Mapping Service and adopted 1950 by NATO for world mapping with a formalised set of parameters and grid origins There are 5 defined spheroids but for Europe and much of the world International is used reference OSGB various publications SNYD Lambert Conical Orthomorphic or Lambert Conformal Conic Is a conic projection with the apex above the north or south pole and the parallel s intersecting the earth at the point of contact Useful for areas or countries of large east west extent Used for aeronautical charts UK Admiralty charts and in France and French colonies Not suitable for large area accurate mapping references Bomford Geodesy SNYD Oblique Mercator Cylindrical projection with the cylinder skew to the earth s axis Similar properties to Transverse Mercator Used for countries with large diagonal extent eg Alaska and Borneo The method used is from reference MP AWM using exponential instead of hyperbolic functions reference SNYD Rectified Skew Mercator As for Oblique Mercator but the grid origin is at a distance from the projection origin New Zealand Developed specifically for New Zealand using Cauchy Riemann equations with coefficients based on the Mercator projection Published by the NZ survey reference New Zealan
90. tum a complete equipotential surface is formed named the geoid which would corresponds to the mean sea level in open ocean and conceptually to that level that would be measured in land bore holes or cuttings connected to the oceans Using satellite surveying methods this has been determined accurately and to be useable in very accurate land surveying or navigation is represented using spherical harmonics This datum was defined in 1996 and is known as EGM96 The supplied coefficients and algorithms allow the height difference between the WGS84 spheroid and the geoid to be calculated at any point on the earth Land surface heights The geoid and the datum it represents is important in the use of land surface heights As mentioned above heights were historically measured in a way that gave heights above the geoid Using satellite surveying methods the basic uncorrected heights are above the spheroid So a knowledge of the geoid to spheroid separation at the point is needed if the new measurements are to be reconciled with the historic or even recent map ones Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 6 20051015 Azimuth Systems User Guide AZGCORR Put simply the geoid to spheroid separation is important if we wish to correct images to fit with data or maps created using traditional surveying methods but can be ignored if all data is produced using purely satellite methods Contemporary satellite surv
91. ysis and display programs Supported output formats are BIL BSEQ Sun raster TIFF GeoTIFF as well as ascii space separated multiplexed vector flat files Selection of data may be by HDF file item name spectral bands pixel or line limits 7 2 basic use Use At unix prompt type azexhdf options h hdf_file_path Usage information obtained by executing program with no command line parameters 7 3 options and parameters option h fp hdf file path fp file path for input hdf file to access option hg vg vgroup to list vg Vgroup name for single vgroup access hg not present all vgroups listed default option hd vd vdata to list vd single vdata to list file option B fp convert image data to BIL binary file fp file path for created file option BS fp convert image data to BSEQ binary file fp file path for created file option Be creates an ENVI compatible header file fp file path for created file option Bv verbose detail listing for conversion switches on verbose listing mode for BIL or BSEQ file creation option Bs requests output header stats file creates a header file during a BIL file output must be used with B file will be fp bil stats option Bh c requests output histogram to header stats file for all data Remote Sensing Scanner Processing System c Azimuth Systems 1996 2005 Version 3 00 34 20051015 Azimuth Systems User Guide AZGCORR c number of columns in histogram c 0 g

AZGCORR - Airborne Research & Survey Facility

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AZGCORR - Airborne Research &amp; Survey Facility

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AZGCORR - Airborne Research & Survey Facility