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1. The Calculate dialog allows you to provide a label to identify the results of each calculation you perform and a comment to annotate the calculation for example to describe why you have chosen particular settings for this calculation The label appears on each of HemiView s output sheets together with a sequence number alongside the calculated results The comment appears on the Comments sheet but only if you have selected the Comments sheet as one of the output sheets in the calculation settings as we have in this tutorial Otherwise HemiView ignores any comment which you enter in the Calculate dialog The Calculate dialog also allows you direct the results to an existing workbook window or to create a new one 3 Enter a label and comment highlight Book in the Workbook list to append a new set of results to the existing workbook and click OK 4 Examine the results sheets Observe how a row of values has been added to the Values Image Site and Lens sheets and how tables of values have been added to each the other selected output sheets Notice also how the arrangement of output sheets in the workbook matches the order of the selected items in the Output Sheets tab and that no results have been appended to the Summary or other sheets which you de selected in the Output Sheets tab The ISF Indirect Site Factor and DSF Direct Site Factor are the proportions of direct and diffuse radiation respectively rela
2. Toggle between Classified and full colour image display menu command View Classified Toggle the Skymap overlay on or off menu command View Skymap Toggle the Sunmap overlay on or off menu command View Sunmap Toggle the Daytrack overlay on or off menu command View Daytrack Toggle the Alignment overlay on or off menu command View Alignment B le a ls e a Calculate Toolbar Contains buttons for working with calculations 5 Calculate results using the selected image current alignment and other settings ns fcheck you have an image open and selected al Toggle between the Image and an associated Workbook menu command Window Image and Window Workbook Site List Toolbar Typical view of Site List toolbar Site Cambridge had Cambridge Davis Lawrence The Site List toolbar allows you to select a site for the image in image window provided that image window is active menu command Settings Site Select Click on the toolbar with the right mouse button to bring up a menu which allows you to add and delete sites to the site list and to examine and modify the properties of the current site Lens List Toolbar Typical view of Lens List toolbar Lens Linear 180 The Lens List toolbar allows you to select a lens name from the list of available lenses menu command Settings Lens Select Click on the toolbar with the right mouse button to bring up a menu t
3. diameters of treefall gaps 9 Diffuse Distribution 32 diffuse radiation 31 36 41 55 57 59 60 63 DirBe 38 direct radiation 38 41 56 DISCLAIMER 69 Distance in a hemispherical photograph 9 distortions 12 30 DSF 17 34 38 41 55 58 DSFU 40 E effective LAI 18 ELADP 19 Equiangular Projections 8 Errors 11 59 Excel 34 External Solar Flux 32 F Field protocol for photograph acquisition 50 field records 52 Film 10 12 24 47 50 Film Processing 53 forest 54 60 forest edge 56 forest fires 57 G Gap Fraction 14 16 38 57 60 65 Global radiation 36 Global site factor 17 36 Glossary of Terms 36 GSF 17 36 56 H habitat 55 62 64 Height 9 27 48 50 56 59 heights of trees 9 Hemispherical photography 5 54 Hemispherical Projections 7 History of Hemispherical Photography 6 Humid Tropics 52 humidity 52 hurricanes 57 hvs 28 34 43 Image 3 19 24 32 38 41 50 57 59 65 70 Image acquisition 50 Image analysis 10 12 65 Image digitisation 10 Index e 77 Image Sheet 35 42 image window 24 35 41 43 indices 14 17 54 59 63 65 Indirect site factor 17 36 38 41 58 Installing 4 interpolation between point samples 57 Inversion Models 17 ISF 17 30 34 36 38 41 55 58 J jpg 1 24 27 43 L Label 35 41 52 LAI Models 17 59 Latitude 16 31 leaf angle distribution 18 Lens 22 30 37 41 43 47 50 53 61 63 Lens Calibration 9 lens equ
4. 29 31 T Technical Support 68 Temporal patterns 54 57 66 tga 1 three dimensional geometry 10 58 threshold 11 23 25 42 52 Threshold Method 11 Threshold toolbar 23 32 tif 1 Time Series 23 40 45 TimeSer 40 45 Toolbars 21 24 43 TotBe 39 transects 54 transmittivity 32 treefall gaps 9 52 54 Hemiview User Manual U Uniform Overcast Sky 32 Uninstalling 4 Units 32 41 V Values 11 19 25 30 34 35 45 56 Values Sheet 36 39 variation in solar radiation regimes 16 55 View 21 26 28 29 32 43 45 50 Viewsheds 7 W WARNING 70 Weather and Lighting Considerations 52 WH 27 Width 27 Windows 3 20 58 workbook 34 41 X X Y co ordinate 25 XY 25 Y yellow filters 51 YPlant 45 57 Z Zenith 14 16 25 30 36 39 45 Hemiview User Manual Index e 79
5. 35 mm film combined with the use of a high resolution scanner can be better than a lower resolution digital camera This must be balanced against the benefit of real time feedback from the use of digital cameras Alignment with co ordinate system horizon circle size x y translation of horizon circle rotation relative to North The error considerations are similar to those mentioned above for aligning the camera The accurate registration of the horizon circle on screen requires some care Image Analysis classification distinguishing visible sky from obscured sky image editing enhancement calculation assumptions 12 e Tutorial 1 Introduction to Hemispherical Photography Hemiview User Manual The interactions between all sources of error are complicated and so it is not possible to give guidance on accuracy requirements for individual applications Hemiview User Manual Tutorial 1 Introduction to Hemispherical Photography e 13 Indices Derived from Hemispherical Photographs Hemispherical photographs can be analysed to derive a variety of useful indices geometric indices of visible sky and sky obstruction in particular gap fraction as a function of sky direction solar radiation indices based on geometry and fundamental physical properties of solar radiation canopy indices such as leaf area index LAI Gap Fraction What is Gap Fraction Gap fraction is the proportion of visible sky within a given sky
6. Control Panel 3 In Control Panel double click on AddorRemove Programs 4 In the Install Uninstall tab click the Install button and follow the on screen instructions You will be prompted to enter the serial number This can be found on the HemiView CD Uninstalling HemiView To uninstall Hemiview 1 From the Start Menu select Settings Control Panel 2 In Control Panel double click on Add Remove Programs 3 In the Install Uninstall tab highlight HemiView in the list of installed programs click the Add Remove button and follow the on screen instructions Hemiview User Manual Tutorial 1 Introduction to Hemispherical Photography What is Hemispherical Photography Hemiview User Manual Hemispherical photography provides an upward looking view of all or part of the sky Typically hemispherical images are acquired with either a standard film camera or a digital camera fitted with a hemispherical fisheye lens pointed upward The resulting photographs provide a permanent record that can be analysed to determine which parts of the sky are visible and which parts are obstructed by landscape features plant canopies or human built structures Based on these measurements of the geometry of sky visibility and sky obstruction hemispherical photographs can be used to calculate solar radiation regimes and plant canopy characteristics such as Leaf Area Index LAI Hemispherical photography can greatly expand the number of field
7. DISCLAIMER Hemiview User Manual You may make one copy of HemiView for backup purposes You may NOT make copies of HemiView nor allow copies to be made for distribution or resale You may NOT offer 1t for hire or rental or any other purpose other than the legitimate purposes listed above Due to the complex nature of HemiView and although HemiView has been tested for quality and defect free performance prior to sale a Delta T do not warrant that HemiView will operate completely free of error nor that it will operate without interruption or that it is compatible with all computer hardware and operating system configurations b Delta T shall have no liability or responsibility to the user of Hemi View co operator or any other person or entity with respect to any liability loss or damage caused or alleged to have been caused directly or indirectly by HemiView including but not limited to any interruption of service loss of business or anticipatory profits indirect special or consequential damages arising out of its use or any obligations arising through its usage c Delta T do not make any warranties whatsoever as to the fitness of HemiView to be used for any purpose The entire risk associated with using Hemi View is with the customer co operator or any other persons who use Hemi View for any purpose Technical Support e 69 CREDITS COPYRIGHT and NOTICES WARNING HemiView is protected by copyright law and internationa
8. E M Adomeit and S J Witts 1980 PISCES a computer program for analysing hemispherical canopy photographs CSIRO Technical Memorandum 80 23 Canberra p 25 Kappel F and G H Neilsen 1994 Relationship between light microclimate fruit growth fruit quality specific leaf weight and N and P content of spur leaves of Bartlett and Anjou pear Scientia Horticulturae 59 3 4 187 196 Labbe P 1994 Regeneration in tropical rain forests of Guadeloupe after the passage of hurricane Hugo Acta Oecologica 15 3 310 315 Landry R R A Fournier R Lang and F J Ahern 1997 Tree vectorization a method to describe tree architecture Canadian Journal of Remote Sensing 23 2 91 107 Lang A R G 1986 Leaf area and average leaf angle from transmittance of direct sunlight Australian Journal of Botany 34 349 355 Lang A R G R E McMurtrie and M L Benson 1991 Validity of surface area indices of Pinus radiata estimated from transmittance of the sun s beam Agricultural and Forest Meteorology 37 229 243 Lang G E and K Freissler 1992 Clinical and fluorescein angiographic findings in patients with branch retinal vein occlusion An unicentric study on 211 patients Klinische Monatsblaetter Fuer Augenheilkunde 201 4 234 239 Lasko A N 1976 Characterizing apple tree canopies by fisheye photography HortScience 11 404 405 Tutorial 4 Case Studies e 63 64 e Tutorial 4 Case Studies Lasko A N 1980 Cor
9. HemiView always needs the image file to be available in the same folder as the hvs file Starting HemiView in your Working Directory When you are working on real projects it is good practice to create a working directory on your hard drive for your work That is keep your data separate from the actual HemiView program You will probably want to create or modify a HemiView icon which starts up HemiView in your working directory 1 Highlight the HemiView icon and click the right mouse button to display the icon s popup menu 2 From the popup menu select Properties 3 Select the Shortcut tab and enter the name of your working directory in the Start In box Hemiview User Manual Start up HemiView can also be started by double clicking a hvs file in Windows Explorer or dragging and dropping an image hvs or xls file icon onto a HemiView icon or its shortcut icon Toolbars Hemiview User Manual Start HemiView either by choosing HemiView in the Start Programs Menu or by double clicking on a desktop shortcut to HemiView MEE Toolbars provide quick mouse access to many tools used in HemiView Typically toolbars are displayed across the top of the application window below the menu bar Toolbars can also be moved by dragging the border of the toolbar to the desired location while holding down the left mouse button To display or hide toolbars choose View Toolbar and click toolbar
10. If a camera and lens are stored in an air conditioned environment they should be heated above outside temperature before use in the field Otherwise water will condense on the cold surfaces When working in the hot humid tropics of Costa Rica Paul Rich used a dry box which consisted of a cabinet that was heated by a series of incandescent light bulbs and placed within an air conditioned laboratory This dry box was kept at a temperature above the outside temperature while in equilibrium with the lower humidity air of the laboratory thus providing a good environment for camera and lens storage Film should be processed promptly after taking hemispherical canopy photographs Prompt processing allows one to assess the quality of the photographs and to go back and retake any photographs that are not of suitable quality In some cases it may be desirable to develop the film in the field especially when working in isolated field sites where it may not be possible to retake photographs in the future Many commercial film processors now offer services to scan photographs and place them directly in Kodak PhotoCD format at reasonable costs Typical Film Processing Protocol 1 Load film into developing tank in dark room or film loading bag 2 Fill tank with developer develop for 8 minutes in small tank or 9 minutes for large tank agitate 4 turns per agitation 2X per minute for small tank or 1X per minute for large tank Pour o
11. S W markers the pointer changes to a double headed arrow pointing along the circumference of the circle This indicates that you can rotate the horizon circle by dragging Try these operations holding down the left mouse button and dragging the horizon circle 4 While dragging the horizon circle observe how the status bar changes to present detailed information about the image alignment For Hel pees Fl Ta Net SO Cee RY it WH width and height of the image Rad radius of the horizon circle Centre XY X Y co ordinates of the centre of the horizon circle Rot the rotation of the image measured in the direction of increasing azimuth angle i e anti clockwise when looking up at the sky You can also adjust the size and position of the horizon circle using shortcut keys as follows 5 Hold down the Shift key and press one of the keyboard arrow keys to move the horizon circle 6 Hold down Shift and Alt and press the up or down arrow keys to adjust the size of the horizon circle 7 Hold down Shift and Alt and press the left or right arrow keys to adjust the rotation of the horizon circle 8 Add the Ctrl key to the above key strokes to make larger movements In the picture file Samplel jpg the direction of magnetic North and South is indicated by two small dome shaped lights on the horizon In this picture these were created by two LEDs Light Emitting Diodes mounted on the camera s self le
12. The Astronomical Almanac Published annually by United States Government Printing Office Washington and The Stationery Office London Baret F B Andrieu and M D Steven 1993 Gap frequency and canopy architecture of sugar beet and wheat crops Agricultural and Forest Meteorology 65 3 4 261 279 Barrie J D J N Greatorex R J Parsell and R H Marrs 1990 A semi automated method for analysing hemispherical photographs for the assessment of woodland shade Biological Conservation 54 4 327 334 Bates J W 1992 Influence of chemical and physical factors on Quercus and Fraxinus epiphytes at Loch Sunart western Scotland A multivariate analysis Journal of Ecology 80 163 179 Becker P 1987 Monthly average solar radiation in Panama daily and hourly relations between direct and global insolation Solar Energy 39 445 453 Becker P F and A P Smith Spatial autocorrelation of solar radiation in a tropical moist forest understory Agricultural and Forest Meteorology Becker P D W Erhart and A P Smith 1986 Operator s Manual Canopy Photo Analysis System Smithsonian Tropical Research Institute Unpublished Manuscript Becker P D W Erhart and A P Smith 1989 Analysis of forest light environments Part I Computerized estimation of solar radiation from hemispherical canopy photographs Agricultural and Forest Meteorology 44 217 232 Bellingham P J E V J Tanner P M Rich and T C R Goodland 1996 Ch
13. and analysis Image acquisition typically involves taking hemispherical photographs using a film camera looking upward from a location of interest e g from beneath a plant canopy Images may also be acquired by calculation using a simulation model that accounts for three dimensional geometry Image digitisation typically involves conversion of a film photograph an analogue format into digital format In the case of HemiView film negatives can be digitised using a negative scanner a video framegrabber or other analogue to digital conversion device In the case of digital cameras or video cameras connected to a framegrabber image acquisition and digitisation are combined into one step the analogue to digital conversion occurring at the time the image is acquired Image analysis involves four steps 1 classification of images to distinguish visible and obscured sky directions e g for canopies to distinguish canopy openings from foliage 2 calculation of sky visibility and obstruction as a function of sky direction 3 calculation of solar radiation and or canopy indices using this information about sky visibility and obstruction 4 output of results Image Acquisition and Digitisation Typically hemispherical photographs are acquired through standard film cameras and then negatives or positives are digitised using scanners video digitizers or other analogue to digital conversion technologies Recently digital came
14. and on days with evenly overcast skies A high quality hemispherical lens should be used High quality hemispherical lenses and rugged cameras are manufactured by several companies including Sigma Canon Minolta and Nikon The Sigma 8mm lens represents excellent value in terms of quality relative to price Other components include a camera body e g Nikon FM2 a databack that automatically imprints a unique number in the corner of each negative e g Nikon MF16 A camera fitted with an internal meter can facilitate determination of exposure For quality hemispherical canopy photographs excellent results have been obtained with either black and white e g T Max 400 Ilford HPS or colour film e g Ektachrome 400 Additional Supplies Hemiview User Manual A good shoulder satchel is useful for carrying supplies necessary for hemispherical canopy photography including film data notebooks pens or pencils a compass lens cleaning supplies spare batteries and plastic bags A good compass is necessary for orienting the camera assembly relative to north For cleaning the lens and camera it is wise to carry cleaning brushes lens cleaning fluid and lens tissue Spare batteries should be carried for the camera light meter and databack In case of rain sufficient plastic bags should be carried to enclose all equipment A folding umbrella can also be useful to protect the equipment Tutorial 3 Field Protocols e 47 Self Levellin
15. and so is not altered when you open a hvs file It is part of the Output Configuration Next time you Open an image Output configurations ie sets of calculation settings solar models sites and lenses are available for use by all images HemiView saves them in configuration files Config csv Models csv Sites csv Lenses csv in the Hemi View installation directory when you exit Hemi View so they are preserved for the next time you run HemiView The names of the image site and lens are saved to a hvs HemiView Settings file whenever you save an image in HemiView so that when you open a hvs file HemiView automatically locates the image file and the appropriate lens and site in its lens and site lists The hvs file contains the name of an image file only and not the image itself so the image needs to remain alongside the hvs file in your working directory Tutorial 2 Using HemiView e 43 The hvs file contains the names of the site and lens and not the site or lens properties so 1f you delete or modify the properties of the site or lens within HemiView you will not be able to reproduce earlier results when you next open the hvs file The hvs file does not contain solar model properties or calculation settings HemiView always uses the currently selected solar model and output configuration for its calculations 44 e Tutorial 2 Using HemiView Hemiview User Manual Calculating Time Series and Sunfleck Duration He
16. and simpler transport between sites When using a monopod it is best to also use a self levelling camera mount A monopod can be held at maximum extension of the arms to obtain photographs up to 2 5 or 3 0 m above the ground 48 e Tutorial 3 Field Protocols Hemiview User Manual In addition a monopod and self levelling mount set up can be used from ladders to take photographs at greater heights using tall folding aluminium step ladders Hemiview User Manual Tutorial 3 Field Protocols e 49 Similarly a monopod and self levelling mount set up enables work at even greater heights using such techniques as Swedish climbing ladders and a climbing harnesses Optional Equipment for Camera Orientation and Location of Photograph Edges Various researchers have found it useful to use lights in the field of view to facilitate camera orientation or to assist in identifying the edges of photographs A bright lamp mounted on a pole can be held in the direction of magnetic north to serve as a reference when positioning the film in rotation during digitisation A set of lights attached to the camera mount at the edge of the field of view can assist with locating the edge of the field of view during digitisation Protocol for Image Acquisition 50 e Tutorial 3 Field Protocols A standardised field protocol should be adopted for acquisition of hemispherical canopy photographs thus ensuring uniform quality of photographs for analysis Field
17. black visible sky as white and ignored pixels if any in the ignored colour The image is not degraded by this action Repeating any of the above actions restores the original view of the image Toggling the Classified view on and off whilst adjusting the Threshold is a good way of deciding the best Threshold setting 2 To determine the best threshold setting you may find it useful to display classified and full colour views side by side Select the Window New command Change the classified state of one of the windows and re size and arrange the two images side by side Change the Threshold 3 Adjust the threshold Experiment with each of the following methods ise Ta 3 Press or keyboard shortcut keys to increase or decrease the threshold value e Hold down Ctrl while pressing or to increase or decrease the threshold value in larger steps e Drag the Threshold toolbar slider with the mouse e Click the up and down buttons of the Threshold toolbar e Enter a numeric value directly into the Threshold toolbar e Choose the Settings Classifier command and select a threshold value in the Classifier Settings dialog as in the Threshold toolbar Note that the Classifier Settings dialog allows you to preview and cancel any changes you make to the threshold value Also the Classifier Settings dialog allows to select a colour value for HemiView to ignore Hemiview User Manual Tutorial 2 Using HemiView
18. button From the popup menu select Properties Examine its properties Press Cancel after you have finished examining the properties 2 Turn on the sunmap by clicking the button 3 Select other sites from the Site List toolbar Examine the properties of each and observe how the sunmap changes depending on the latitude 4 Observe how the magnetic north marker remains fixed on the LED while the position of true north varies with the magnetic declination of the site 5 Select the Settings Site command and choose New Enter the following settings Site Name Wild Place Latitude 10 5 West Longitude 20 3 South magnetic declination 30 1 West altitude 200 Description test location Click OK and examine how the sunmap overlay shifts 6 Scroll through the Site List using the Site List toolbar and observe that Wild Place has been added to the list 7 To delete the site select Burwell for the active image HemiView won t allow you delete a site which is in use by an image From the Site List popup menu select Delete In the Delete Site dialog highlight Wild Place and click OK Scroll through the sight list and observe that Wild Place is no longer in the list 8 Turn off the sunmap overlay by clicking the sl button again HemiView uses a model to estimate how much solar radiation will be received both directly from the sun and diffuse radiation from the whole sky and over the whole period of interest This could be a
19. day a month or a year HemiView s solar model calculates solar radiation conditions from the solar constant the quantity of solar radiation incident on the surface of the earth s atmosphere and two numerical values which characterise local atmospheric conditions the fraction transmitted to the earth s surface sea level with the sun at the zenith and the proportion scattered to become diffuse light the remainder being reflected Combining these with the latitude altitude and date and time HemiView calculates how much of the direct beam will be scattered or absorbed on its way to the surface and how much will be seen as scattered light from the rest of the sky As with sites and lenses use either the commands in the Settings Solar Model menu or the Solar Models toolbar to choose a solar model change the properties of a solar model or create a new solar model Tutorial 2 Using HemiView e 31 Simple Model Molz i Classify Image 32 e Tutorial 2 Using HemiView 1 From the Solar Models toolbar select Default Simple Model 2 Bring up the Solar Models popup menu by placing the mouse pointer on the Solar Models toolbar and clicking the right mouse button From the popup menu select Properties Examine the three tabs in the Solar Model Properties dialog 3 Observe that Energy units are selected on the Solar Model tab You may choose Molar units which are appropriate for many plant scientis
20. diffuse radiation for an open location no sky obstruction See also direct site factor DSF and global site factor GSF insolation Equivalent to incoming solar radiation leaf angle distribution The distribution of inclination and azimuth angles for leaves The inclination angle is measured between the perpendicular to the leaf surface and the zenith The azimuth angle is measured between a horizontal projection of the leaf perpendicular and true North leaf area index LAI For broad leaf vegetation the surface area of leaves per unit ground area For broad leaf vegetation only the upper or only the lower surface area is counted For conifers with round or square cross sections or other non flat leaves LAI is calculated as the total leaf surface area all sides of leaves divided by two all per unit ground area LAI is widely used in models that examine productivity and transpiration since both are generally proportional to the leaf area photosynthetic photon flux density PPFD Incident photon flux density of PAR the number of photons 400 700 nm wavelength incident per unit time on a unit surface The SI unit is mol m 2 s 1 Usually the units of micromol m 2 s 1 or microEinsteins m 2 s 1 not part of the SI system are used photosynthetically active radiation PAR Solar radiation in the 400 700 nm waveband These wavelengths can be used by green plants in photosynthesis PPFD Photosynthetic Photon Flux
21. foliage Chen et al 1991 suggests that a clumping factor can be used to account for this non random distribution such that LAI is simply multiplied by a stand specific clumping factor to calculate a more realistic LAI In practice LAI and LAI are nearly identical in broadleaf canopies i e clumping factors are near unity however in conifer canopies where there is strong clumping it becomes necessary to estimate the clumping factor by either direct of indirect means Chen and Cihlar 1995 Chen et al 1995 The LAI estimated by the inversion process may not be an exact measure of the LAI of the real canopy even if that could be measured accurately However an ideal canopy with the LAI estimated will behave in a very similar way to the real canopy as far as radiation interception is concerned Leaf Angle Distribution The same models that permit calculation of LAI also permit calculation of leaf angle distribution Leaf angle distribution refers to the distribution of LAI between leaves of each angular orientation 18 e Tutorial 1 Introduction to Hemispherical Photography Hemiview User Manual HemiView LAI Calculations Introduction Campbell 1986 derived an equation for the extinction coefficient of canopy elements distributed in the same proportions and orientation as the surface of an ellipsoid of revolution symmetrical about a vertical axis The semi vertical axis is a and the semi horizontal axis is b
22. hemispherical photographs as input for an individual crown model for light capture and carbon gain by understory plants YPlant model Either empirical or simulated hemispherical photographs can be used for simulations with the model In essence light capture was calculated using gap fraction in each sky direction as input to a diffuse radiation submodel and timing of sunflecks along the sun track as input in a direct radiation submodel The three dimensional distribution of all leaves on a plant are specified along with physiological parameters such as light response curves Interception Tutorial 4 Case Studies e 57 efficiencies and carbon gain were compared under different light regimes for an understory species and a forest edge species The edge species had more self shading within the crown while the understory species was more efficient at capturing light from directly above The YPlant model has been enhanced significantly since this study and has been rewritten as a Windows program that uses the HemiView TSeries and TSkyGap as input This modelling approach opens a new frontier for understanding ecophysiology crown architecture and life history strategies Solar radiation interception by canopies 58 e Tutorial 4 Case Studies Solar radiation interception involves the same calculations as do analyses of solar radiation regimes beneath the canopy but with a focus on what radiation is blocked rather than what radiation pene
23. moisture as a function of canopy position south edge of canopy under canopy north edge of canopy and intercanopy In essence this study enabled characterisation of distinct gradients of microclimate that occur in predictable ways depending upon position beneath the canopy Tutorial 4 Case Studies e 55 56 e Tutorial 4 Case Studies Vertical transects and changes in available light with height growth Lerdau M T Holbrook N M H A Mooney P M Rich and J L Whitbeck 1992 Seasonal patterns of acid fluctuations and resource storage in the arborescent cactus Opuntia excelsa in relation to light availability and size Oecologia 92 166 171 Hemispherical photographs taken along vertical transects can be used to determine differences in solar radiation regimes experienced by plants growing at different heights within the canopy This study involved taking photographs at a series of heights within a deciduous forest with transects repeated during leaf on and leaf off periods Additional sets of photographs were taken to characterise the light available to tree cactuses growing at different heights within the canopy The forest displayed an exponential increase in light availability with height and a marked increase in light available to the understory during the leaf off period Cactuses growing at a particular height were found to have higher light levels than the forest in general at that height Acquiring photographs in verti
24. nono nono nono nono nonnncnncrancrnncnnnnns 52 Permanent Photograph Slt8S ooooocnnnnnncnnoonnonnonnnonnconoconoco nono nooo no nono nnnonnncnn cnn nnnnnnnn canon necnnes 52 Special Methodology for the Humid Tropics ooooooccnoccconcconononononnnannnnnnnnoconoco noc nccn ccoo no naninns 52 Film ProcessiOS iia cos te a An 53 Typical Film Processing Protocol oooonncnnncnocnnocnnononanconnconoconocono cono no nono nrnncrnnonns 53 Photograph Archiving a riene a e E E E e RE E E 53 Tutorial 4 Case Studies 54 Solar radiation regimes below the CanOPY coooconocconnconononnnononancnncconoconocnnco noc noc nooo ccoo nc nnnonns 54 Solar radiation regimes and site indices for treefall gaps versus closed canopy VOCATIONS R A EEE o iio ias 54 Solar radiation regimes or site indices as they relate to plant ecophysiology and PEO Wire tii E A 55 Site factors as they relate to habitat suitability for animal species 00 55 Solar radiation regimes along transects and soil moisture in heterogeneous O E aes ete 55 Vertical transects and changes in available light with height growth 56 Using multiple transects to compare spatial patterns in different forest stands 56 Two dimensional maps of solar radiation from arrays of photographs multiple A O EEEE E AAT E TE addecdsuelsedtiped eee 56 Monitoring temporal changes in solar radiation regimes after major disturbance EVENTS A NN 57 SuMleck Odia iii iia 57 Using sunfleck re
25. nooo nono no nn nono nrnn cnn o nnnnnnnnnnn cn necnneo 47 AS A a theca donk eee ete ape eee eee 47 Palin ss cl ites ita E atten del Soa ee ead aig A ee eR ee 47 Additional Supplies see csecescossenseensosscssenssesseessecsevcnee e EE E T 47 Self Levelling Camera Mount eee ceeeseecseeeeeeeeeeeeeeeeeeceeeeseeeseeeseesecaecaecsaeesaesaaeees 48 Camera Positioning Equipment eee eeccecesecesecesecnsecaecasecseesseesaeseaeeseeeeeesrenseeeaees 48 Optional Equipment for Camera Orientation and Location of Photograph Edges 50 Protocol for Image Acquisition ooooocnconnccnocnnonnconoconoconocnncnnnornnonn nono ncnn cnn conc conc cnn cnecnnecnneos 50 Field protocol for photograph acquisition ooooococcnocnnocnnoccconoconocononononncnnncnnonanonos 50 Preparations Prior to Going into the Flield ononnnnncnonononcnononononanonncnncnanonanonan cano rancnnnono 51 Camera Positioning and Orientation oooononnnnnncnnnonconnnonoconocnnonn conoce nnnonnncnncrnn cnn cnn ncnnncnnncnnes 51 Photograph Exposure ooooococconnconononononoconoconocnonnnonnnonn ccoo non conc Eeoa on nono conocio nn ncnnccnnnns 51 Taking Photographs cooooocnnncnocnconnconoconoconocononnnonononn nono nnnnnnnnnnn nc deoii aioa ei eein 51 Use of Camera DatabackKs oooncononcnococoncconoconcnnncnnnnanonanonncnn non no cono cn nooo corn nonnccnncnnos 52 Field Records ias da Sas aS 52 Weather and Lighting Considerations oooonccnonnnonnnonnnonnnonconnconoco
26. of a fish eye lens to study nest placement in Franklin s gulls Ecology 53 2 362 363 Burger J 1976 Nest density of the black headed gull in relation to vegetation Bird Study 23 1 27 32 Burger J 1977 Role of visibility in nesting behavior of Larus gulls Journal of Comparative and Physiological Psychlogy 91 6 1347 1358 Campbell G S Extinction coefficients for radiation in plant canopies calculated using an ellipsoidal inclination angle distribution Agricultural amp Forest Meteorology 36 1986 317 321 Canham C D J S Denslow W J Platt J R Runkle T A Spies and P S White 1990 Light regimes beneath closed canopies and tree fall gaps in temperate and tropical forests Canadian Journal of Forest Research 20 620 631 Canham C D 1989 Different responses to gaps among shade tolerant tree species Ecology 70 3 548 550 Canham C D 1995 A manual for GLI C Canham C D A C Finzi S W Pacala and D H Burbank 1994 Causes and consequences of resource heterogeneity in forests interspecific variation in light transmission by canopy trees Canadian Journal of Forest Research 24 337 349 Chan S S R W McCreight J D Walstad and T A Spies 1986 Evaluating forest vegetative cover with computerized analysis of fisheye photographs Forest Science 32 1085 1091 Chazdon R L and C B Field 1987a Determinants of photosynthetic capacity in six rainforest Piper species Oecologia 73 222 230 Chazdo
27. protocol for photograph acquisition 1 Set up assemble camera and lens in mount set ASA load film place assembly on tripod or monopod remove lens cap 2 Position and level camera assembly at proper height above ground 3 Orient camera assembly to magnetic north 4 Set exposure time and aperture 5 Take photograph using the camera self timer Hemiview User Manual 6 Repeat steps 2 4 Preparations Prior to Going into the Field Before going into the field all equipment and supplies should be assembled and tested A checklist of equipment and supplies should be reviewed Sufficient film should be placed in a sealed plastic bag For efficiency film canisters can be labelled ahead of time Similarly data notebooks can be partially filled out ahead of time The camera light meter and databack should both have good sets of batteries Camera Positioning and Orientation Hemiview User Manual The camera must be properly positioned levelled and oriented before the exposure is determined and the photograph is taken Proper positioning includes correct location horizontally and vertically whereas orientation refers to rotation of the camera relative to north First the camera should be positioned above the correct horizontal location Then the camera should be raised or lowered to the proper height In cases where the camera is very close to the ground it may be necessary to crouch or even lie down to get out of the lens fiel
28. 0 80 70 80 50 40 30 20 Zenith Angle degrees 10 e 0 0 0 2 0 4 0 6 DB 1 0 Propartian of Radial Distance Other Hemispherical Lens Projections More generally any hemispherical lens produces an image in which the zenith is in the centre of the image the maximum view angle is at the edges of the image 8 e Tutorial 1 Introduction to Hemispherical Photography Hemiview User Manual Hemiview User Manual and intermediate locations represent intermediate zenith angles Itis possible to precisely locate any intervening sky direction in the resulting hemispherical photographs HemiView accounts for the projection used by a particular lens by fitting a polynomial that translates location within the photograph to sky direction represented by zenith and azimuth angle Lens Calibration A lens correction function for a given lens can be calculated empirically or in some cases determined from specifications provided by the lens manufacturer Herbert 1986 1987 For calculations using HemiView a polynomial is used to calculate the proportion of radial distance from the centre of the image as a function of zenith angle The curve is constrained to pass through 0 and 90 degree zenith angles at radial distances of O and 1 respectively The following graph shows the lens calibration for the Sigma hemispherical lens Note that the dotted line shows a perfect equiangular projection while the solid line shows the Sigma lens projection No
29. 4 511 523 Olsson L D Carlsson H Grip and K Perttu 1982 Evaluation of forest canopy photography with diode array scanner OSIRIS Canadian Journal of Forest Research 12 822 828 Pearcy R W 1983 The light environment and growth of C3 and C4 tree species in the understory of a Hawaiian forest Oecologia 58 19 25 Hemiview User Manual Hemiview User Manual Pearcy R W 1989 Radiation and light measurements pp 95 116 In R W Pearcy J Ehleringer H A Mooney and P W Rundel eds Plant Physiological Ecology Field Methods and Instrumentation Chapman and Hall New York Pearcy R W and H W Calkin 1983 Carbon dioxide exchange of C3 and C4 tree species in the understory of a Hawaiian forest Oecologia Berlin 58 26 32 Pearcy R W L J Gross and D He 1997 An improved dynamic model of photosynthesis for estimation of carbon gain in sunfleck light regimes Plant Cell and Environment 20 41 1 424 Perry S G A B Fraser D W Thomson and J M Norman 1988 Indirect sensing of plant canopy structure with simple radiation measurements Agricultural and Forest Meteorology 42 255 278 Pfitsch W A and R W Pearcy 1992 Growth and reproductive allocation of Adenocaulon bicolor following experimental removal of sunflecks Ecology 73 6 2109 2117 Poorter L and S F Oberbauer 1993 Photosynthesis induction responses of two rainforest tree species in relation to light environment Oecologia Heidelberg 96 1
30. 72 276 Yamamoto T and H Itoh 1996 A measurement of tree form and canopy structure of densely planted dwarf apple trees using two sides photographs taken at right angle with wide angle lenses Journal of the Japanese Society for Horticultural Science 64 4 729 739 Tutorial 4 Case Studies e 67 Technical Support Contacts LICENCE 68 e Technical Support On Line Help Use the on line Help once the HemiView software is installed on your PC as your first port of call Use the Help menu or press F1 Readme txt Read the Readme txt file in your HemiView directory for the latest information about bug fixes and changes This may be more up to date than the user manual www delta t co uk Visit our web site for technical support news Distributor contact If you have a problem please call your local distributor first Before you call It will help considerably if you can first fax through as many relevant details as possible In particular a description of the fault the symptoms and any error messages what components of the HemiView system you are using details of any PC you are using software version numbers and serial number of any hardware Direct Delta T contact Contact Technical Support at Delta T directly on Tel 44 0 1638 742922 Fax 44 0 1638 743155 Email tech support delta t co uk Web site http www delta t co uk You may install HemiView on a single computer Hemiview User Manual
31. 93 199 Pope D J and P S Lloyd 1974 Hemispherical photography topography and plant distribution pp 385 408 In G C Evans R Bainbridge and O Rackham eds Light as an ecological factor II Blackwell Oxford Raaimakers D R G A Boot P Dijkstra S Pot and T Pons 1995 Photosynthetic rates in relation to leaf phosphorus content in pioneer versus climax tropical rainforest trees Oecologia Berlin 102 1 120 125 Reifsnyder W E 1967 Radiation geometry in the measurement and interpretation of radiation balance Agricultural and Forest Meteorology 4 255 265 Reifsnyder W E G M Furnival and J L Horwitz 1971 Spatial and temporal distribution of solar radiation beneath forest canopies Agricultural Meteorology 9 21 37 Rich P M 1988 Video image analysis of hemispherical canopy photography In P W Mausel ed First Special Workshop on Videography Terre Haute Indiana May 19 20 1988 American Society for Photogrammetry and Remote Sensing pp 84 95 Rich P M 1989 A manual for analysis of hemispherical canopy photography Los Alamos National Laboratory Report LA 11733 M Rich P M 1990 Characterizing plant canopies with hemispherical photographs In N S Goel and J M Norman eds Instrumentation for studying vegetation canopies for remote sensing in optical and thermal infrared regions Remote Sensing Reviews 5 13 29 Rich P M D B Clark D A Clark and S F Oberbauer 1993 Long term stu
32. Delta T Devices Ltd Hemiview User Manual Notes a pre Revision Number 2 1 and Te omamunicaton Cante pdas the Kansas eric care pe econ ET paa Ps nas Biological Survey Trademarks Excel and Windows are trademarks of Microsoft Corporation Contact Delta T Devices Ltd 128 Low Road Burwell Cambridge CB5 OEJ UK Tel 01638 742922 interaaienal 44 1638 742922 22 Fax 01638 743155 international 44 1638 743155 e mail sales delta t co uk Contents Introduction 1 A O 1 Features IO AAA A 1 Install HemiView 3 SYSTEM CA vbsdbencts eopesblsdiessedesshess 3 Installing or Removing HemiView c cc eesceecceesseceeeeecsseceseeesaeceeneeesaeceeeesaeceeneseaeceaees 4 Tutorial 1 Introduction to Hemispherical Photography 5 What is Hemispherical Photography ooocnncnnncnocnnonnnoncnonccnnonnnonnnonncnnn crono nnnnnncnn non ne cn nocnnoo 5 Hemispherical Photography as Upside Down Remote Sensing oooocnnccncncnnncns 5 Some Applications of Hemispherical Photography oooconcnncnnncnonnnonononcnononanonoss 5 Hemispherical Images as Permanent Records of Sky Visibility and Obstruction 6 Brief History of Hemispherical Photography oooocnnnnnnnnnnnnnnnonnconnconncn nc cnn nono nono conc cnnncnnnons 6 Hemispherical Co ordinate SySteM oooconcccoccconnnoncnononononnnonncnononononononn cnn conc nnnnnnn non n nn nera nncnnnos 7 How Are Sky Directions Represented oo eee eeceescesecssecseecseeceeeneeeeseeeee
33. Density Incident photon flux density of PAR the number of photons 400 700 nm wavelength incident per unit time on a unit surface The SI unit is mol m 2 s 1 Usually the units of micromol m 2 s 1 or microEinsteins m 2 s 1 not part of the SI system are used Glossary of Terms e 73 74 e Glossary of Terms productivity The formation of biomass matter originating from living organisms Primary productivity refers to the biomass formed in photosynthesis or chemosynthesis from solar energy carbon dioxide water and mineral nutrients Gross productivity refers to the total biomass formed per unit area or unit volume for aquatic systems whereas net productivity refers to the biomass formed after losses by respiration are accounted for In terms of energy gross productivity of the entire Earth s biosphere is estimated at 6 53 x 10 KJ yr 1 This is equivalent to an average gross productivity per unit area of 12 8 MJ m 2 per year or 35 0 KJ m 2 per day 0 405 W m 2 Average daily solar radiation intercepted at Earth s surface is 17 0 MJ m 2 day 1 Hence gross primary productivity of all the ecosystems of the world has an overall efficiency of 0 207 Net productivity is considerably less than gross productivity since respiration consumes on the average 3 81 x 10 KJ of the 6 53 x 10 KJ of gross productivity per year giving a value of 2 72 x 10 KJ for net productivity When divided by the earth s surface area this is eq
34. Model Output Configuration Toolbar Typical view of the Output Configuration Toolbar Output Config n Tutorial y Tutorial Uncorrected Dutput Y The Output Configuration Toolbar allows you to select from a predetermined list of Output Configurations each of which may represent a different combination of calculation settings and Output Sheets These may be inspected in detail and edited via the menu command Settings Output Configuration Tutorial 2 Using HemiView e 23 Open an Image 24 e Tutorial 2 Using HemiView HemiView can handle several standard image file formats Choose File Open Select the file Sample1 jpg from the Samples directory under the HemiView installation directory and open it This is a greyscale image from a JPEG format file scanned in from a 35 mm black and white film The image opens in its own image window EPT alaja cjela e 3 7 10 e E a l a MALA ae Theta FF E RGE 35 31 35 M5 Samplel jpg also showing a pop up menu enabled by clicking right mouse button Observe that various toolbars have now become available for the display and analysis of images Reduce the size of the image window Try reducing the image down to an icon Enlarge the image window to fill the entire available area Right click somewhere on the image and observe the pop up menu appear as shown above This pop up menu duplicates some of the commands in th
35. The case studies supplied above represent a sampling of the range of uses of hemispherical photography but can not be comprehensive New uses will continually be developed and depend upon the problems being addressed as well as on ingenuity Clearly more research is needed in all of the areas mentioned above The technique is sufficiently well developed that with care it can yield excellent results At the same time neither the limitations nor the opportunities of the technique have been fully explored From a technique standpoint much work is still needed Systematic studies are needed to compare results from HemiView with other software used for analysis of hemispherical photography to compare results according to image resolution and to compare results with different films and camera settings Further research is needed concerning alternative algorithms for image classification alternative direct and diffuse models sensitivity to incorporation of month to month variation in cloudiness importance of diffuse radiation anisotropy non uniform distribution according to sky direction and alternative LAI models Rigorous measures of errors need to be developed and standards need to be established to enable comparisons of results from different study sites Finally studies of hemispherical statistics promise to prove fruitful Hemiview User Manual Tutorial 4 Case Studies e 59 References 60 e Tutorial 4 Case Studies Ackerly D D a
36. There is symmetry about the vertical axis He relates these to a single parameter x b a x is the Ellipsoidal Leaf Angle Distribution Parameter or ELADP The extinction coefficient also depends on the zenith angle of the incoming direct beam Canopy elements are assumed to be completely black and randomly distributed in a horizontal slab extending to infinity in all directions This model can be used to represent a wide variety of different canopies by choosing an appropriate LAI and ELADP An ELADP greater than represents a canopy where the elements are predominantly horizontal and less than 1 represents a canopy where the elements are predominantly vertical Hemiview LAI Inversion Hemiview finds the values of LAI and ELADP for an ellipsoidally distributed theoretical canopy that give the best fit to the measured gap fraction values from the hemiphoto These best fit values are then used as a basis for subsequent calculations in the LAI group This gives a robust and widely applicable result but will not necessarily accurately reflect particular cases such as bimodal distributions where the canopy is a mix of two very different types of canopy element HemiView estimates the effective LAI so this value may need to be multiplied by a clumping factor to give an accurate estimate of actual LAI Analysis of partial images There are situations where users may wish to ignore part of an image from the analysis e g if the horizon is not
37. anges in light below the canopy of a Jamaican montane rainforest after a hurricane Journal of Tropical Ecology 12 699 722 Hemiview User Manual Hemiview User Manual Boes E 1981 Fundamentals of solar radiation Chapter 2 In J F Kreider and F Kreith eds Solar Energy Handbook McGraw Hill New York Bonhomme R 1973 Analyse de la surface des taches de soleil de l indice foliaire et de l inclinaison moyenne des feuilles a l aide de photographies hemispheriques pp 369 376 In R O Slatyer ed Plant response to climatic factors UNESCO Paris Bonhomme R and P Chartier 1972 The interpretation and automatic measurement of hemispherical photographs to obtain sunlit foliage area and gap frequency Israel Journal of Agricultural Research 22 53 61 Bonhomme R C Varlet Granger and P Chartier 1974 The use of hemispherical photographs for determining the leaf area index of young crops Photosynthetica 8 299 301 Breshears D D P M Rich F J Barnes and K Campbell 1997 Overstory imposed heterogeneity in solar radiation and soil moisture in a semiarid woodland Ecological Applications 7 1201 1215 Brown B 1993 The implications of climate and gap microclimate for seedling growth conditions in a bornean lowland rain forest Journal of Tropical Ecology 9 153 168 Brown H E 1962 The canopy camera USDA Forest Service Rocky Mountain Forest and Range Experiment Station Paper 72 Burger J 1972 The use
38. ations 9 Lens Projections 8 Lens Selection 30 Lens Toolbar 30 lights 27 48 50 Linear 180 30 Long 16 54 56 65 Longitude 31 magnetic north 10 26 31 50 Methods 11 33 45 56 59 60 62 64 microclimate 55 61 63 microeinsteins 16 MTA 59 N Negative 10 22 24 43 47 53 Nikon Coolpix camera 28 Nikon SLR 8mm lens 48 North 10 12 26 31 36 39 47 50 55 66 O On Line Help 36 68 Open an Image 24 Output Configuration Toolbar 23 P PAR 16 54 57 pcd 1 pcx 1 Photograph Exposure 51 photon flux density 16 62 photosynthetic photon flux density 16 62 photosynthetically active radiation 16 61 Problems 11 59 78 e Index R Rad 27 Red filters 51 References 60 resolution 3 12 46 59 Results 16 22 32 34 40 47 57 59 RGB 25 Rot 27 S segmenting an image 11 Self Levelling Camera Mount 48 self levelling mount 27 48 self levelling mounts 48 Settings Lens 22 Shortcut Keys 23 24 27 33 Show Image 22 30 shutter speed 51 Sigma 8 mm 30 simulation model 10 site 12 19 22 28 31 36 41 43 54 57 68 Site Factors 12 15 17 55 Sites csv 43 Site Specific 16 sky visibility 10 17 skymap overlay 22 29 soil moisture 55 61 Solar Model 23 31 Solar Models Toolbar 23 31 Solar Transmission 32 Spatial patterns 54 56 Standard Overcast Sky 32 Status Bar 25 27 succession 58 Summary 35 41 Sunfleck 12 23 40 45 57 65 SunGap 36 41 sunmap overlay 22
39. butterflies select overwintering sites that have a suitable canopy structure to protect them from wind rain and major temperature fluctuations while also allowing sufficient solar radiation in the spring Hemispherical photography proved to be a valuable tool for habitat assessment and use in conservation management decisions By simulating potential impacts of tree removal on butterfly habitat it was possible to assess different management scenarios concerning proposed modifications to forest stands Solar radiation regimes along transects and soil moisture in heterogeneous canopies Breshears D D P M Rich F J Barnes and K Campbell 1997 Overstory imposed heterogeneity in solar radiation and soil moisture in a semiarid woodland Ecological Applications 7 1201 1215 Hemispherical photographs taken along horizontal transects can be used to determine variation in solar radiation regimes as it relates to variation in canopy structure and also to examine ecosystem measurements that correspond with this spatial heterogeneity This study examined relations between the overstory solar radiation regimes and soil moisture for photographs taken every meter along a one hundred meter transect Solar radiation and soil moisture showed autocorrelation at spatial scales that correspond to heterogeneity of canopy versus intercanopy patches A complex set of factors interception evapotranspiration insolation lead to predictable patterns of soil
40. cal transects is challenging especially for tall canopies but has been accomplished successfully by various researchers Using multiple transects to compare spatial patterns in different forest stands Clark D B D A Clark P M Rich S B Weiss and S F Oberbauer 1996 Landscape scale evaluation of understory light and canopy structure methods and application in a neotropical lowland rain forest Canadian Journal of Forest Research 26 747 757 Photographs taken at intervals along multiple long transects can be used to assess spatial patterns and assess the distribution of understory light environments at a landscape level This study involved taking hemispherical photographs along fifteen 100 m long transects to sample variation in a tropical wet forest photos taken at 2 5 m intervals for heights of one and three m above the ground and at 0 6 and five m heights at five stations for each transect Photographs were analysed to determine GSF Spatial autocorrelation Moran s I test was observed to be significant for GSF at distances of about 20 m under a canopy that was observed to have a median height of 23 m Values for the random background understory light environment of the forest at large proved useful as the reference when evaluating the conditions observed for saplings of tree species with different life histories Two pioneer species occurred in microsites with solar radiation levels that were significantly higher than the fo
41. computers The following is a listing of system requirements Operating System Microsoft Windows NT v 4 0 Windows 95 Windows 98 Memory RAM Minimum 16 Mbytes Recommended 32 Mbytes of RAM to improve calculation performance Larger images require more RAM Storage hard disk Minimum HemiView requires approximately 10 Mbytes of free space for installation Recommended 20 Mbytes to 2 Gbytes Considerable disk space can be required for handling images Video Display Minimum 16 colour VGA Recommended 800 x 600 24 bit true colour or 16 bit high colour display adapter with hardware accelerated panning Superior operation can be achieved with a higher resolution adapter e g 1024 x 768 true colour Other Features Mouse trackball or other pointer device required CD ROM drive essential writeable CD tape backup or other mass storage device optional for archiving large image files Install HemiView e 3 Installing or Removing HemiView 4 e Install HemiView The HemiView files include a program called Setup exe which automatically installs HemiView on your computer Once installed a HemiView installation can be removed by following the simple procedure described below Installing HemiView To run the installation program Setup exe which is provided on the HemiView distribution CD do the following 1 Start Windows Insert the HemiView CD in an appropriate drive 2 From the Start Menu select Settings
42. d of view Then the camera should be levelled if a self levelling mount is not used After the camera is positioned and levelled correctly the orientation should be adjusted so that magnetic north is located directly toward the top of the image This can be accomplished in various ways For example one can affix a compass to the monopod or camera mount and rotate the assembly until the compass lines up correctly Alternatively one can first locate a reference object toward magnetic north and then sight along an edge of the camera mount to achieve proper orientation Photograph Exposure An internal camera light meter can be used to obtain consistent exposures First the ASA should be properly set on the camera When working with black and white film photographs should be taken using a blue filter to enhance contrast between visible and obscured sky direction Red filters can also help to increase contrast in a desirable way However yellow filters should be avoided because they tend to increase contrast within the sky in particular accentuating clouds and uneven lighting Blue and red filters tend to increase contrast between foliage and canopy openings Metering must be done with the filter in place When metering the exposure it is often necessary to temporarily move the camera from its correct position and make adjustments of the shutter speed and aperture After making adjustments the camera should be returned to its correct position and
43. dent diffuse radiation 1t shows how the available diffuse light varies in space and can be applied to either instantaneous radiation values or values integrated over some time interval The Sunmap matches the track of the sun throughout the day and through the year so it divides the hemiphoto into areas representing time When combined with incident direct radiation values it shows how direct radiation varies over time It is because of these differences that the Sunmap and Skymap use different units when radiation values are calculated Solar Radiation Indices What are the Main Types of Solar Radiation Incoming solar radiation insolation can potentially originate from a visible sky direction as either of two types direct radiation radiation passing unimpeded through the atmosphere from the sun and diffuse radiation solar radiation that is scattered by the atmosphere One consequence of having visible sky in a given direction is that direct and diffuse solar radiation can pass unimpeded from that direction On the other hand obscured sky directions represent directions where solar radiation can not be transmitted directly however reflected radiation can originate from canopy elements in those directions Global radiation is defined as the sum of direct diffuse and reflected radiation reaching a particular location Under most circumstances the majority of insolation reaching a given location originates as direct o
44. diation under a plant canopy relative to that in the open total site factor of Anderson 1964 Typically calculated as direct plus diffuse radiation with reflected radiation ignored You should similarly be able to find on line definitions for direct site factor DSF and indirect site factor ISF 7 Click on the SkyGap tab Samplez tes fle ole F 5 H I J al 5 Zenith ho 500 Ha ima 1004 2 04 2 04 00 6 28 0043 0011 Gifs 006 00 00004 fies 0 0650 T TB ame gira gme 0113 0837 000 Daa owr 01437 t E 000 003 0111 Oe www 00 0100 007 00 0072 Diea gta 0442 00 0067 pisa Om 0007 ga 042 037 006 007 02 035058 0013 D 0485 046 Oe 0156 000 0673 Ow A Dm 0182 O26 OS 003 ost aS 0330 OND 00 L ee ral it 13 yal 014 036 0181 03 Oe 03 030 00 bi 14 25 oma 01E 023 0407 00682 Oz 0254 os 0417 8 02315 00 044 037 003 037 Oe 000 0104 16 S28 0182 0006 0410 03567 00 OO OM CS 05 17 s75 02 Na dA 0347 0067 0712 Os foo DTS A 25 020 0477 0 45 03A 006 017 0103 DHE 014 19 78 0470 0173 02 4 eT Mi 00753 0142 Oe 0168 Fill es 0342 O48 O40 06 og 033 018 om3 0353 ral TS 038 Oiz oo 0003 Qw 0794 0104 us 0341 7 35 0085 012 00 008 amig t7 0137 0 34 Fl 8 O00 gwa On 0 ES US D DWE fr The SkyGap sheet shows how much of each cell in the skymap appears obstructed expressed as a decimal fraction Each column maps onto a radial section of the SkyMap starti
45. dy of solar radiation regimes in a tropical wet forest using quantum sensors and hemispherical photography Agricultural and Forest Meteorology 65 1 2 107 127 Rich P M D M Ranken and J S George 1989 A manual for microcomputer image analysis Los Almos National Laboratory report LA 11732 M Rich P M J Chen S J Sulatycki R Vashisht and W S Wachspress 1995 Calculation of leaf area index and other canopy indices from gap fraction a manual for the LAICALC software Kansas Applied Remote Sensing Program Open File Report Robichaux R H and R W Pearcy 1980a Environmental characteristics field water relations and photosynthetic responses of C4 Hawaiian Euphorbia species from contrasting habitats Oecologia 47 99 105 Tutorial 4 Case Studies e 65 66 e Tutorial 4 Case Studies Robichaux R H and R W Pearcy 1980b Photosynthetic responses of C3 and C4 species from cool shaded habitats in Hawaii Oecologia 47 106 109 Russell G B Marshall and P G Jarvis eds 1989 Plant canopies their growth form and function Cambridge University Press Schecter I D C Elfving and J T A Proctor 1991 Apple tree canopy development and photosynthesis as affected by rootstock Canadian Journal of Botany 69 2 295 300 Smith A P K P Hogan and J R Idol 1992 Spatial and temporal patterns of light and canopy structure in a lowland tropical moist forest Biotropica 24 4 503 511 Sparks T H D J N Greator
46. e 33 Inspect Results 34 e Tutorial 2 Using HemiView Classifier l Ignored Pixels E I Ignore this Colour Red 255 ES Green fi Blue fi lV Preview Settings Cancel Help 4 Toggle Classified on and off using the C shortcut key Examine how well the two views match in terms of visible and obscured sky directions Adjust the threshold to better match the original image view Repeat these steps until you are satisfied that the image is well classified Note that consistency in choosing a threshold takes practice and is among the most challenging issues when analysing hemispherical photographs Consistency in image classification depends upon using high quality photographs and adopting consistent criteria for trade offs between best representing distinctions between foliage and visible sky in different parts of the image For many projects a set of 10 20 reference photographs is used to train users and periodically to evaluate whether repeated analyses are consistent In addition many users of hemispherical photographs repeat analyses of all photographs two or more times until consistently repeatable results e g ISF or DSF values are obtained HemiView can compute a wide range of results placing each type of result in its own worksheet within an Excel 5 0 compatible workbook First we select an existing output configuration so we can have a quick look at some results 1 Open Sample2 hvs using the F
47. e alignment overlay on again 3 Toggle on the skymap overlay using E The Skymap divides the whole sky into sky sectors and is used for calculations of diffuse solar radiation ISF and LAI all of which require information about all sky directions Select Settings Skymap and observe the current settings Set the azimuth divisions to 16 and the zenith divisions to 30 and click OK Observe how the skymap overlay changes Set the azimuth divisions to 8 45 degree divisions and zenith divisions to 18 5 degree divisions and click OK This is the setting typically recommended for analysis of hemispherical photographs Observe how the skymap overlay changes Toggle the skymap overlay off 4 Select View Show Image to toggle the image display off Observe that the Sunmap Overlay remains on This feature can be useful to produce graphical illustrations of overlays without having to load a blank image Select View Show Image again to redisplay the image Toggle off the Sunmap Overlay using the button 5 Toggle on the daytrack overlay using the j button Observe the value in the Day of Year toolbar Toggle the daytrack overlay off Experiment with entering different values in the Day of the Year toolbar and their effect on the daytrack overlay The daytrack overlay enables examination of the path of the sun on any given day through the year Lens information is used by Hemi View to correct for any distortions in mapping from the zenith an
48. e corrections will be in error determined by the number of degrees out of level and that part of the image below the horizon will not be measured or will be measured incorrectly If you are studying sunflecks and trying match predicted and actual sunfleck patterns on a particular day then you have to be very accuratelty aligned If your alignment is out by the equivalent of one solar disk half a degeree then you will be in error for the calculated times and position of the sunfleck In practice it is quite difficult to achieve half a degree accuracy in horizontal aligment and so you should be as careful as possible The main point to remember is that you need a higher alignment accuracy for accurate sunfleck predictions than for for broad global meaurements such as LAI site factors and gap fractions Exposure sky lighting evenness foliage lighting evenness Reflections can occur if the sun is lighting up the underneath of some of the leaves This is one reason for taking pictures when the sun is just below the horizon Glossy leaves can give reflections from bright portions of sky even when the direct sun is not visible Optical distortion To a large extent Hemiview takes out optical distortions for the recommended lenses Image quality resolution and digitisation For a given image the highest achievable resolution and colour depth are best Digitising film will add some noise and lose resolution but even so good quality
49. e main menu and also shows shortcut keys as follows Negative N Classified Alignment Skymap Sunmap UCR YEO Daytrack Hemiview User Manual Hemiview User Manual The visible sky in this image is fairly uniform Later in this tutorial when you come to classify the image by setting a threshold grey scale level representing the boundary between clear and obstructed sky you will need the sky illumination to be as uniform as possible When classifying the image you will not want large variations in brightness in the sky and so you particularly will not want to see the sun in the photo The problem is that an obstruction such as a leaf in bright sunlight in one part of the sky may appear brighter than a dull part of the visible sky somewhere else The best time to take pictures is before sunrise or after sunset or on a day when the sky is uniformly overcast with cloud Move the mouse pointer over the image and observe the values changing in the Status Bar at the bottom of the window ForHelp press FI XV 194 135 AZ 544 839 RGB 28 26 28 VIS A The status bar presents detailed information about each pixel under the pointer e XY X Y co ordinate of the cursor shown as 194 135 pixels from the top left of the picture e AZ azimuth and zenith angle co ordinates in degrees e RGB Red Green Blue intensity value 0 0 0 is black 255 0 0 is bright red 255 255 255 is white plus an indication of whethe
50. e this manual to get started with HemiView It covers the following Getting Started Installing the software Tutorial 1 Introduction to Hemispherical Photography essential background for understanding and using HemiView effectively Tutorial 2 Using the HemiView Software supplemented by comprehensive on line help Tutorial 3 Field Protocols about good experimental techniques Tutorial 4 Case Studies Technical Support Glossary of Terms In addition to the above the on line Help includes sections on Windows and Menu Commands Calculations Theory Files Features of HemiView Hemiview User Manual HemiView is a Windows based program designed for convenient image analysis of hemispherical photography HemiView supports the following image file formats Windows or OS 2 BMP bmp JPEG jpg PC Paintbrush PCX pcx TIFF tif TARGA tga and Photo CD pcd Full Windows compatibility enables the user to place digital images and analysis results in the clipboard and to paste graphics and data directly in documents or graphics presentations Image display toggles between original and classified views permits real time display of negatives as positive images and provides for overlay of skymaps sunmaps and daytrack maps A horizon circle marked with cardinal points and magnetic North along with an interactive alignment mode enables precise registration of images with the hemispherical co ordinate s
51. eneees 7 Lens Cala bration sitios tai leonesa 9 Why Hemispherical Photographs Represent Angles Not Distance o 9 Basic Steps of Hemispherical Photography oooocononcnonccocononononcnancnnco nono no nono nono no nono nina conos 10 Image Acquisition and Digitisation eee eee eeceseceseceecesecesecsaecsaesseeceeeaeeeaee 10 Classification Of IMa ges ccssecscrssciscaeactonedebivenesonsdansbanserscoyasussedensveensensteysdendeteeons 11 Compounding Of Errors ococococcncnnoonconnconoconocnoconono conan cnn cnn ais E E cone EES eiS 11 Indices Derived from Hemispherical Photograpbs ooooconnccnonccconccnonnconncconnncnnccnonnccnnncc no 14 Gap Fraction incipiente ie ii ee eee 14 Solar Radiation Indices essenin ese ane EEE aE E E a S ees 15 The Basic Model for Estimation of Solar Radiation oooononcnonnnonononcnnncnncnanonaninnos 15 Site Factors from Hemispherical Photograpbs ooncnnccnnnnnonononnconcconconoconocanccnnos 17 Leaf Area Index from Hemispherical Photograpbs ooooconnccconccinnccconcnonanacanenon 17 Analysis of partial IMAgeS ooooocnnononocconcnononnnonnnonnnonn nono conc non nono cono co nono nc nano rn nena nino 19 Tutorial 2 Using HemiView 20 Setup your Work folders ini a a dci 20 Starting HemiView in your Working Directory ooonocconcnnnnnnnnonnnonncnnnconoconccanocnnos 20 O 21 MOO DAMS 52 SS 21 Standard Toolbar lira 21 Mew Toolbar assi iii 21 Calculate Toolbar aiii ii 22 Site List LOO DAU it
52. entirely within the image area or part of a building or crane is visible or to exclude trunks and branches from a LAI estimate Hemiview allows you to paint parts of an image in a colour which is then ignored by the hemiphoto analysis Areas ignored in this way can be visualised as an additional mask between the sky hemisphere and HemiView Gap fractions site factors and LAI are calculated using only the information in the valid part of the image Radiation values both above and below the canopy are reduced by the amounts that would have come from the ignored areas Hemiview User Manual Tutorial 1 Introduction to Hemispherical Photography e 19 Tutorial 2 Using HemiView Set up your work folders 20 e Tutorial 2 Using HemiView The HemiView installation program creates a directory named Samples under the HemiView installation directory and a Windows shortcut which will start up HemiView in the Samples directory The Samples directory contains the files you will need for this tutorial Two of them are image files Samplel jpg and Sample2 jpg There is also a third file in your Sample folder called Sample2 hvs This is not an image file Later in the Tutorial you will be asked to load it Itis a HemiView Settings file created by using the File Save command It contains information about the Sample2 jpg image file but does not actually contain a copy of the image itself A point to remember when organising your work folders
53. ex J O Mountford M L Hall and R H Marrs 1996 The effects of shade on the plant communities of rides in plantation woodland and implications for butterfly conservation Forest Ecology and Management 80 1 3 197 207 Sprugel D G J R Brooks and T M Hinckley 1996 Effects of light on shoot geometry and needle morphology in Abies amabilis Tree Physiology 16 1 2 91 98 terSteege H HEMIPHOT a Programme to Analyse Vegetation Indices Light and Light Quality from Hemispherical Photographs Tropenbos Turner I M 1990 Tree seedling growth and survival in a Malaysian rain forest Biotropica 22 146 154 Turton S M 1988 Solar radiation regimes in a north Queensland rainforest Proceedings of the Ecological Society of Australia 15 101 105 Turton S M and G A Duff 1992 Light environments and floristic composition across an open forest rainforest boundary in northeastern Queensland Australian Journal of Ecology 17 4 415 423 Ustin S L R A Woodward M G Barbour and J L Hatfield 1984 Relationships between sunfleck dynamics and red fir seedling distribution Ecology 65 1420 1428 Vertessy R A R G Benyon S K O Sullivan and P R Gribben 1995 Relationships between stem diameter sapwood area leaf area and transpiration in a young mountain ash forest Tree Physiology 15 9 559 567 Walters M B and C B Field 1987 Photosynthetic light acclimation in two rainforest Piper species with different ecol
54. f Botany 15 141 144 Mitchell P L and T C Whitmore 1993 Use of hemispherical photographs in forest ecology calculation of absolute amount of radiation beneath the canopy Oxford Forestry Institute Oxford United Kingdom Moon P and D E Spencer 1942 Illumination from a nonuniform sky Illuminating Engineering 37 707 726 Morris D M G B MacDonald and K M McClain 1990 Evaluation of morphological attributes as response variables to perennial competition for 4 year old black spruce and jack pine seedlings Canadian Journal of Forest Research 20 11 1696 1703 Murren C J and A M Ellison 1996 Effects of habitat plant size and floral display on male and female reproductive success of the Neotropical orchid Brassavola nodosa Biotropica 28 1 30 41 Neumann H H and R H Shaw 1989 Leaf area measurements based on hemispheric photographs and leaf litter collection in a deciduous forest during autumn leaf fall 45 325 345 Nikon Product brochure for Nikkor 8 mm fish eye lens Norman J M and G S Campbell 1989 Canopy structure pp 301 326 In R W Pearcy J Ehleringer H A Mooney and P W Rundel eds Plant physiological ecology field methods and instrumentation Chapman and Hall London Oberbauer S F D B Clark D A Clark P M Rich and G Vega 1993 Light environment gas exchange and annual growth of saplings of three species of rain forest trees in Costa Rica Journal of Tropical Ecology 9
55. ff developer new to used bottle or used to discard Rinse in running water for 1 minute and then drain Fill tank with stop bath leave for 1 minute agitate 2X Pour stop bath back into bottle discard if purplish indicator Rinse in running water for 1 minute Fill tank with fixer agitate 15 seconds per minute for 10 minutes Ce NDA A amp Pour off fixer into appropriate bottle 10 Open tank rinse in water for 20 minutes 11 Rinse in photo flo and hang negatives to dry Photograph Archiving Hemiview User Manual Once negatives are dry they should be properly stored and labelled Typically it is best to use archive quality negative storage sheets that hold six strips of six photographs each These negative storage sheets can be stored in standard three ring binders Negatives can be easily examined without removal from the storage sheets Negatives that are to be analysed can be temporarily removed As with any photographic materials negatives should be stored in a cool dark location Tutorial 3 Field Protocols e 53 Tutorial 4 Case Studies Solar radiation regimes below the canopy 54 e Tutorial 4 Case Studies Most of the early work with hemispherical photography and much of the current work involves calculation of site indices or solar radiation regimes beneath plant canopies Commonly hemispherical photographs are used as a means to evaluate differences between study locations Photo
56. forest edge on experimental growth plots being set up in the clearing While it is practical to produce such maps in gaps or clearings maps under forest canopies are more challenging because high variation of conditions under canopies often occurs at very fine spatial scales and interpolation between point samples may not be valid Monitoring temporal changes in solar radiation regimes after major disturbance events Bellingham P J E V J Tanner P M Rich and T C R Goodland 1996 Changes in light below the canopy of a Jamaican montane rainforest after a hurricane Journal of Tropical Ecology 12 699 722 Major disturbances such as hurricanes or forest fires can cause a mosaic of forest patches at different successional states Hemispherical photography has proven useful for monitoring changes that occur after disturbances This study examined landscape scale changes in understory solar radiation after Hurricane Gilbert in 1988 Hemispherical photographs were taken at permanent sampling locations at four sites during the course of 33 months after the hurricane A total of 25 sample locations were distributed among the four sites and photographs were acquired at ten time intervals between seven and 33 months after the hurricane PAR was calculated for each photograph with calculated values calibrated to long term sensor measurements above the canopy During the first 24 months after the hurricane PAR beneath the canopy was significantly g
57. from each part of the sky even when the surface is horizontal Scientists normally work with radiation readings as they would be received by a perfect flat black body surface or aperture at a given orientation Most people will expect to receive cosine corrected results If you are unsure assume you are with the majority and choose the corrected i e cosine corrected results All HemiView outputs with the U suffix e g DSFU are not cosine corrected U is for Uncorrected and for Unusual When would you use it If you were interested in modelling the radiation absorbed by a non flat surface such as human or animal you may wish to take the raw uncorrected data and project it onto a cylinder or map it directly onto a hemispherical object such as a ladybird 40 e Tutorial 2 Using HemiView Hemiview User Manual Calculate Results Hemiview User Manual In previous sections we opened aligned and classified the image and specified which calculations HemiView will perform 1 Ensure that your image window is the active window click on its title bar if in doubt or select it from the Window menu Note that the Calculate button is only enabled if the active window is an image window 2 Use one of the following to start the HemiView calculation e Select Calculate from the menu bar e Click the Calculate gt toolbar button Before proceeding with the calculation HemiView pops up the Calculate dialog
58. g Camera Mount A self levelling camera mount can greatly facilitate photograph acquisition A self levelling mount is essential for situations where hemispherical canopy photographs are taken high above the ground or in awkward positions However even when acquiring photographs near ground level a self levelling mount makes photograph acquisition much easier In terms of design the mount 1s suspended in a set of gimbals wherein there are two axes of free rotation each axis at right angles to the other and parallel to the ground The weight of the camera and lens suspended below the mount causes the mount to level itself An set of weights secured to the bottom of the mount can be adjusted to level the film plane The mount assembly can be supported on a tripod or monopod Delta T can supply self levelling mounts suitable for tripods or monopods Mounts can be supplied for the Sigma 8mm fisheye lens with the Nikon FM2 camera and the Nikon Coolpix950 digital camera and lens These include lights a compass and bubble level for aligning pictures An adaptor is also available for the Nikon SLR 8mm lens but due to its large size this mount does not have lights bubble level or compass Camera Positioning Equipment Placement of the camera assembly on a tripod allows precise positioning but only up to the maximum height of the tripod Support of the camera assembly on a monopod allows one to work up to greater heights and allows quicker set up
59. gimes as an input to ecophysiological models of plants 57 Solar radiation interception by canopies ccooonoccoonconncononannnanonncnnnconoconocn nooo nc onc cn nooo ccoo ncnnninns 58 Solar radiation interception in forest canopies as it relates to succession 58 Solar radiation interception in three dimensional reconstructions of forest e100 SISA A EEE AEE ETTE 58 Recording and analysing structure s esesseesseeseeeseseresrseeereserrrestsrrsesrenresrerreserrresrsrreresreet 59 Comparison of leaf area index of forest stands ooooonncnnncnnccnocnconoconoconcconccnnonnnonn 59 ii e Contents Hemiview User Manual Challenges and Opportunities ocoonocnoncconoconononocononononnnonnnonnnnnnnonnnann cone cn i neon ccoo corn SEa cnn 59 RE ad ae 60 Technical Support 68 Contacts et a ads ta a tds tr det o a a O 68 On Eme HelPirrticnin anilla lis t 68 REAGING 1x tere atten et Lt ad a Nak el 68 OYA AWTACG Co ba 0100 Qs 68 Distributor contact ccococcccncncnnnnnnnnnnnnnnnnnnnononononononononononononononononononononinenininininons 68 Before you Call ic cional EEI aa diese i 68 Direct Delta a manada dad de 68 LICENCE E EE e AIR a A EAE el he T 68 DISCEATMER lt a o e we dota el e E o e ha nh 69 CREDITS COPYRIGHT and NOTICES ccccnnnonononononinonononanonocinonanananononoconanananeneniconannno 70 Glossary of Terms 71 Index 77 Hemiview User Manual Contents e iii Introduction About this Manual Us
60. gle in 3 dimensions to the radius on the two dimensional image Hemi View allows you to specify the type of lens used to create the image either by using the Lens toolbar or by using the Lens command in the Settings menu 1 Select the Settings Lens command In the Select Lens dialog observe which lens is currently selected If not already selected highlight Linear 180 from the list and click OK This is suitable for a Nikon SLR 8mm lens 2 Toggle on the skymap overlay with the ES button Observe the pattern of annuli Leave the skymap overlay on 3 Select the Sigma 8 mm lens from the Lens List Observe as the image overlay is updated and redrawn The Linear 180 and Sigma lenses differ only slightly in their characteristics Can you detect a difference in the position of the annuli Leave the setting with the on Sigma 8 mm lens selected Hemiview User Manual Site Properties Site Burwell v Solar Model Hemiview User Manual In this section we select a site and observe the effect of changing site properties These include latitude longitude magnetic declination and altitude Use the commands in the Settings Site menu or the Site List Toolbar to choose the site for an image change the properties of a site or add a new site to Hemi View s Site List 1 From the Site List select the Burwell Bring up the Site List popup menu by placing the mouse pointer on the Site List toolbar and clicking the right mouse
61. graphs have various advantages over solar radiation sensors including the ability to gather data relatively quickly without need for long term set up of sensors with data logger which also has the implication that hemiphotos can be acquired for a broader range of spatial locations than is practical for sensors Unlike most sensors hemispherical photographs provide direct information about the geometry of the canopy above a site which can be used for understanding causal factors for observed temporal and spatial patterns Further hemiphotos represent a permanent record that can be analysed to obtain many solar radiation and site indices Spatial patterns can be examined by taking photographs at distance intervals in 1 horizontal or 2 vertical transects Temporal patterns can be examined either 1 by calculating future regimes under the assumption that the canopy does not change or 2 by taking repeated photographs at a given location at intervals through time Solar radiation regimes and site indices for treefall gaps versus closed canopy locations Rich P M D B Clark D A Clark and S F Oberbauer 1993 Long term study of solar radiation regimes in a tropical wet forest using quantum sensors and hemispherical photography Agricultural and Forest Meteorology 65 1 2 107 127 One of the primary ways that hemispherical photographs have been used involves comparison of solar radiation regimes or site indices at select sample locations with
62. h photograph the position of the labels can be used as an internal reference for positioning the photographs during digitisation Field records should contain pertinent hemispherical canopy photograph data At minimum field records should include the film roll number unique photograph number as imprinted by the databack and location The location may be a location in a sample grid or transect line or the plant above which a photograph is taken In addition the date time of day exposure settings height above the ground weather or sky conditions and additional notes can be recorded Weather or sky conditions can include such categories as sunny partly cloudy overcast sprinkling and raining Some researchers prefer to write with indelible pens others prefer mechanical pencils that will not fail in the rain Waterproof notebooks are especially useful for humid or rainy study locations Pre printed data sheets can minimise the amount of writing that must be done in the field Weather and Lighting Considerations The ideal condition for taking hemispherical canopy photographs is an evenly overcast sky In the absence of an overcast sky photographs are best taken at predawn or post sunset when no direct sunlight is visible Canopy photographs taken with direct sunlight in the field of view tend to be unevenly exposed with a bright region around the sun and with reflections on foliage or structures Uneven sky lighting makes it difficult
63. herical imagery has required tedious manual analysis using sampling grids Jupp et al 1980 first developed a computer program PISCES for analysis of hemispherical photographs but Pisces still required manual photograph analysis and data entry Automated image analysis was attempted by various researchers Bonhomme and Chartier 1972 Olsson et al 1982 Chan et al 1986 Chazdon and Field 1987 developed a microcomputer analysis system SOLARCALC based on the Apple Macintosh Integrated image analysis systems based on DOS computers in particular the systems CANOPY Rich 1988 and SYLVA Becker et al 1989 were developed to use video for direct input of negatives Most recently several Windows based software packages have been developed for example the program HEMISP Vieglais unpublished HemiView benefits from and has many advantages over these prototype systems These advantages include full Windows compatibility lack of requirement for expensive specialised hardware support of a full spectrum of standard image 6 e Tutorial 1 Introduction to Hemispherical Photography Hemiview User Manual formats rapid and accurate calculation configurable output to spreadsheets flexibility for incorporating site specific information expert technical support and ongoing commitment to the research and development required for improvements and new capabilities Hemispherical Co ordinate System Hemiview User Manual How Are Sky Directions Re
64. ial and temporal variation of light inside peach trees Journal of the American Society for Horticultural Science 119 669 677 Gower S T and J M Norman 1991 Rapid estimation of leaf area index in forests using the LI COR LAI 2000 Ecology 72 1896 1900 Greatorex D J N T H Sparks and M L Hall 1994 The response of Heteroptera and Coleoptera species to shade and aspect in rides of coniferised lowland woods in southern England Biological Conservation 67 3 255 273 Greatorex D J N T H Sparks M L Hall and R H Marrs 1992 The influence of shade on butterflies in rides of coniferised lowland woods in southern England and implications for conservation management Biological Conservation 63 1 31 41 Herbert T J 1986 Calibration of fisheye lenses by inversion of area projections Applied Optics 25 12 1875 1876 Herbert T J 1987 Area projections of fisheye photographic lenses Agricultural and Forest Meteorology 39 215 223 Hill R 1924 A lens for whole sky photographs Quarterly Journal of the Royal Meteorological Society 50 227 235 Hutchinson B A and D R Matt 1977 The distribution of solar radiation within a deciduous forest Ecological Monographs 47 185 207 Hutchinson B A D R Matt and R T McMillen 1980 Effects of sky brightness distribution upon penetration of diffuse radiation through canopy gaps in a deciduous forest Agricultural and Forest Meteorology 22 137 147 Jupp D L B M C Anderson
65. ific distributions of diffuse and direct radiation can be formulated accordingly using empirical or theoretical insolation values appropriate for a particular site Long term monitoring of direct and diffuse radiation for a given site can be accomplished using pyranometers for total radiation or quantum sensors for PAR attached to data loggers For detailed studies two sensors are required one to monitor global radiation flux and a second to monitor diffuse radiation The diffuse radiation sensor must be fitted with a shadowband to block radiation along the sun path Direct radiation is calculated as the difference between observed global radiation flux and diffuse radiation flux The Delta T BF2 Sunshine Sensor has been designed specifically for this purpose 16 e Tutorial 1 Introduction to Hemispherical Photography Hemiview User Manual Hemiview User Manual Site Factors from Hemispherical Photographs What are Site Factors Site factors are indices of the proportion of radiation reaching a given location Values range from 0 to 1 with O being no radiation complete sky obstruction and 1 being the radiation for an open location complete sky visibility no sky obstruction Indirect site factor ISF is the proportion of diffuse solar radiation reaching a given location relative to a location with no sky obstructions diffuse site factor of Anderson 1964 Direct site factor DSF is the proportion of direct solar radiation
66. ile Open command Observe that HemiView has also loaded the alignment and threshold setting 2 Check to see if you agree with the threshold setting We will now define what results we want to see 3 From the Output Configurations toolbar select Tutorial Output Config n Site Factors y Daytrack Gap Fractions Overall Values Radiation below car Site Factors Tutorial ho Uncorrected Dutput Y 4 Click the Calculate toolbar button Hemiview User Manual Hemiview User Manual Note that the Calculate button is only enabled if the active window is an image window If you have a workbook window open for example if you are repeating this section of the tutorial or have been experimenting with HemiView and have created a workbook window first ensure that the active window is an image window click on its title bar or select it from the Windows menu The Calculate dialog will appear as follows Calculate x We will not change anything this time but whilst we are here note that you may type anything you like into the Label and Comment boxes The Label will appear in every results sheet the default offered is the image file name The Comment appears only on one sheet called Comments The Workbook section of this dialog will appear blank the first time On subsequent occassions it will offer you the choice of appending results to an existing workbook or starting a new one Appended results are al
67. in a forest or at different times for the same sample location This study involved taking hemispherical photographs at a series of seven fixed sample locations at ground level within a recent treefall gap and under nearby closed canopy forest of a tropical wet forest Photographs were acquired at each of the sample locations at month intervals through the course of a year which enabled characterisation of changes over time PAR sensors were installed at each of the sample locations and used to monitor insolation continuously over the course of the year The sensor data enabled calibration and validation of PAR estimates from the hemispherical photographs The hemiphoto data enabled understanding of the geometric basis for variation in solar regimes through the year Changes in solar radiation with time were related to seasonal shifts in solar angle with respect to canopy openings variation in atmospheric conditions month to month difference in cloudiness and changes in canopy geometry in particular growth of trees into the gap Hemiview User Manual Hemiview User Manual Solar radiation regimes or site indices as they relate to plant ecophysiology and growth Oberbauer S F D B Clark D A Clark P M Rich and G Vega 1993 Light environment gas exchange and annual growth of saplings of three species of rain forest trees in Costa Rica Journal of Tropical Ecology 9 4 511 523 Hemispherical photographs taken above individual plant c
68. is to choose an intensity value which best separates the visible sky pixels from obstructed pixels leaves tree trunks buildings or whatever To enable Hemi View to accurately classify an image it is essential to have a uniformly lit or overcast sky when taking photographs for analysis by HemiView Otherwise it is possible for areas of visible sky to appear darker than obstructed canopy Hemi View provides a Threshold toolbar which allows you to a select a suitable threshold value for the image and a classified view of the image which is updated immediately when you change the threshold You can easily switch between classified and full colour views of the image or display both views side by side to observe the effect of changing the threshold value You can also designate a colour value which will be ignored in HemiView s calculations Thus you can paint out prominent obstructions such as tree trunks in the designated colour and exclude those areas of the image from calculated results Display the Classified View Hemiview User Manual 1 Use one of the following methods to display the classified view of the image e Select the View Classified command e Press the C shortcut key e Click the Classified toolbar button e Right click on the image and select Classified from the popup menu e Right click on the Threshold toolbar and select Classified from the popup menu The classified view of the image shows obstructed pixels as
69. ky obstruction See also indirect site factor ISF and global site factor GSF elevation angle The angle above the horizon See also zenith angle and azimuth angle equiangular projection A hemispherical projection in which zenith angle is linearly proportional to radial position The resulting circular image has the zenith in the centre the horizons toward the edges and zenith angle increasing linearly from the centre to the edge format Image file format defines how image information is saved to file HemiView handles bit mapped pictures in which the value for each pixel is stored separately Up to 24 bits may be used to represent each pixel depending on the colour depth the simplest being monochrome framegrabber Devices that convert digitise video signals analogue into digital form See digitize analogue digital global site factor GSF The proportion of global radiation under a plant canopy relative to that in the open total site factor of Anderson 1964 Typically calculated as direct plus diffuse radiation with reflected radiation ignored See also direct site factor DSF and indirect site factor ISF global solar radiation The sum of the energy flux densities for direct diffuse and reflected radiation is known as total or global radiation hemispherical photograph Hemispherical canopy photography is a technique for studying plant canopies using photographs taken through a hemispherica
70. l fisheye lens from beneath a canopy looking upward Such hemispherical photographs provide an extreme wide angle view often with up to a 180 degree field of view The photographs can be analysed to determine the geometry of canopy openings and in turn to estimate light beneath the canopy Thus canopy photographs can be used to assess local light environments beneath plant canopies and to infer properties of Hemiview User Manual Hemiview User Manual plant canopies Hemispherical canopy photography is a technique that directly measures canopy geometry and that indirectly estimates light levels incoming solar radiation For any given location at the Earth s surface the incoming solar radiation or insolation consists of three components 1 direct radiation which is transmitted unimpeded along the path between the sun and the Earth 2 diffuse radiation which results from atmospheric scattering from any sky direction and 3 reflected radiation which consists of direct and diffuse radiation that is reflected off surrounding terrain features Insolation is calculated by integrating direct diffuse and reflected radiation components over a specified time interval Also called insolation indirect site factor ISF The proportion of diffuse solar radiation reaching a given location relative to a location with no sky obstructions Values range from 0 to 1 with 0 being no diffuse radiation complete sky obstruction and 1 being the
71. l treaties Copyright O 1998 1999 Delta T Devices Ltd HemiView was developed with assistance from the University of Kansas Information Technology and Telecommunication Center ITTC the Kansas Technology Enterprise Corporation KT EC and the Kansas Biological Survey Copyright O 1996 The University of Kansas Center for Research Inc Copyright O 1996 David A Vieglais Copyright O 1996 1998 Helios Environmental Modelling Institute LLC HemiView contains Formula One 5 0 from Visual Components Copyright 1994 1997 All rights reserved HemiView contains ImgLib dll Copyright c 1994 1996 SimSoft THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE DATA OR PROFITS WHETHER IN AN ACTION OF CONTRACT NEGLIGENCE OR OTHER TORTIOUS ACTION ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE Portions of the ImgLib code are based on XLI Copyright c 1989 1990 1991 1992 1993 Jim Frost Graeme Gill and others Copyright c 1991 Tim Northrup Copyright c 1990 Mark Majhor Copyright c 1989 1990 Kirk L Johnson The author makes no representations about the suitability of this software for any purpose It is provided as is without express or implied warranty TIFF file support i
72. le Sided In general select Double Sided if you are interested in sensors which are sensitive to radiation received on both upper and lower surfaces such as most plant leaves 12 Click on the Daytrack tab The information in this tab is used for time series calculations of the radiation and sunflecks on any day of the year not just the day of the photo Values are calculated every Time Series Increment throughout the day We do not need to enter any values in the Daytrack tab because we have not chosen either a TimeSer or Sunfleck sheet You have now finished configuring the settings for the results Before progressing to Results here is an announcement Uncorrected U as in DSFU does not mean horizontal surface If you want the radiation on a horizontal surface it is a mistake to use the uncorrected radiation values You should use corrected values and declare the surface orientation zenith angle 0 The reason is as follows Radiation is described in two ways in HemiView corrected and uncorrected The uncorrected radiation values presented in HemiView represent the intensity of the radiaiton source in other words the brightness of the sky at different points over the hemisphere and the corrected readings represent the how that is absorbed by a flat surface at a specified angle The conversion from one to the other involves a simple cosine correction but you need to cosine correct the incident uncorrected radiation values
73. lius Cunn C Koch in a partially shaded forest environment Oecologia Berlin 104 3 363 371 Demarchi M W and F L Bunnell 1993 Estimating forest canopy effects on summer thermal cover for Cervidae deer family Canadian Journal of Forest Research 23 11 2419 2426 Dirzo R C C Horvitz H Quevedo and M A Lopez 1992 The effects of gap size and age on the understorey herb community of a tropical Mexican rain forest Journal of Ecology 80 4 809 822 Ducrey M 1975a Utilisation des photographies hemispheriques pour le calcul de la permeabilite des couverts forestiers au rayonnement solaire I Analyse theorige de l interception Annales des Sciences Forestieres 32 73 92 Ducrey M 1975b Utilisation des photographies hemispheriques pour le calcul de la permeabilite des couverts forestiers au rayonnement solaire II Etude experimentale Annales des Sciences Forestieres 32 205 221 Easter M J and T A Spies 1994 Using hemispherical photography for estimating photosynthetic photon flux density under canopies and in gaps in Douglas fir forests of the Pacific Northwest Canadian Journal of Forest Research 24 10 2050 2058 Ehleringer J R C B Field Z F Lin and C Y Kuo 1986 Leaf carbon isotope and mineral composition in subtropical plants along an irradiance cline Oecologia 70 520 526 Evans G C P Freeman and O Rackham 1974 Developments in hemispherical photography pp 549 556 In G C Evans R Bainb
74. lying by PI 180 See also radians diffuse proportion The proportion of above atmosphere solar radiation that appears as diffuse light integrated over the hemisphere diffuse site factor equivalent to indirect site factor ISF diffuse solar radiation Solar radiation scattered by the atmosphere including blue sky reflections from clouds and the bright aureole surrounding the sun See also direct solar radiation digital Information stored as a series of discrete units such that each unit is represented as a numerical binary value in a computer For example standard computer image formats e g bmp tiff jpeg are stored as an array of discrete values corresponding to brightness or colour See also analogue digitize Glossary of Terms e 71 72 e Glossary of Terms The process of converting an analogue signal into digital binary form For example a negative scanner converts photographic negatives analogue to standard computer image formats digital See also analogue and digital direct radiation Direct radiation arrives from the direction of the solar disc and includes a small component scattered directly forward direct site factor DSF The proportion of direct solar radiation reaching a given location relative to that in a location with no sky obstructions Values range from 0 to 1 with 0 being no direct radiation complete sky obstruction and 1 being the direct radiation for an open location no s
75. mage is a negative or positive is also kept in the hvs file So additional information about the image that affect the calculation of results 1s stored in the hvs file but not the actual image itself Information about whether the overlays are to be displayed is not saved in the hvs file The actual properties of the site and lens are not saved in the hvs file HemiView saves the site and lens properties separately in files named Sites csv and Lenses csv in the HemiView installation directory HemiView also saves solar model and output configuration information in files named Models csv and Config csv in the HemiView installation directory Learn about hvs HemiView Settings files 1 If they are not already visible display the site lens and threshold toolbars with the View Toolbar command 2 If the image that you were working on previously is still open use that If not use File Open and select and open Samplel jpg If you have a workbook open click anywhere on the image to select it Save the image as a hvs file using File Save As Close the image window Make a note of the current settings in the Lens Site and Threshold toolbars TDW ER sp Change these settings Hint Drag the Threshold slider to one side with the mouse 8 Reopen the hvs file using File Open and observe all the original toolbar settings restored Note the Day of Year is not image information and is not saved in the hvs file
76. miview User Manual HemiView can plot the track of the sun across the sky on any chosen day of the year the daytrack and calculate the visibility of the solar disk and associated solar radiation values throughout the course of the day The results can be presented as a time series a sequence of instantaneous snapshots taken at regular intervals in the TimeSer sheet or they can be summarised in the Sunfleck sheet as a list of sunflecks with a start and stop times and radiation values integrated over the sunfleck s duration The calculation settings for daytrack calculations are entered in the Daytrack tab of the Calculation Settings dialog The day of interest can also be selected using the Day of Year toolbar and the daytrack can be viewed by selecting the View Daytrack command or by clicking the Daytrack toolbar button For the Sunfleck sheet you just need to select the day of interest For the TimeSer sheet you also need to specify the time interval between results Daytrack time series calculations are used as input by YPlant a computer program for simulating physiological processes in plants Pearcy et al 1997 1 Display the daytrack using one of the following methods e Select the View Daytrack command e Press the D shortcut key e Click the Daytrack toolbar button e Click the right mouse button on the image and select Daytrack from the image popup menu 2 Use the Day of Year toolbar to change the day
77. n R L and C B Field 1987b Photographic estimation of photosynthetically active radiation evaluation of a computerized technique Oecologia 73 525 532 Chen J M T A Black and R S Adams 1991 Evaluation of hemispherical photography for determining plant area index and geometry of a forest stand Agriculture and Forest Meteorology 86 107 125 Chen J M and T A Black 1992 Defining leaf area index for non flat leaves Plant Cell and Environment 15 421 429 Tutorial 4 Case Studies e 61 62 e Tutorial 4 Case Studies Chen J M and J Cihlar 1995 Plant canopy gap size analysis theory for improving optical measurements of leaf area index Applied Optics 34 6211 6222 Chen J M P M Rich S T Gower J M Norman and S Plummer 1997 Leaf area index of boreal forests theory techniques and measurements Journal of Geophysical Research BOREAS Special Issue 102 D24 29429 29444 Clark D B D A Clark and P M Rich 1993 Comparative analysis of microhabitat utilization by saplings of nine tree species in neotropical rain forest Biotropica 25 4 397 407 Clark D B D A Clark P M Rich S B Weiss and S F Oberbauer 1996 Landscape scale evaluation of understory light and canopy structure methods and application in a neotropical lowland rain forest Canadian Journal of Forest Research 26 747 757 Clearwater M J and K S Gould 1995 Leaf orientation and light interception by juvenile Pseudopanax crassifo
78. n ImgLib comes from the Tag Image File Format Library written by Sam Leffler Copyright c 1988 1989 1990 1991 1992 1993 1994 Sam Leffler Copyright c 1991 1992 1993 1994 Silicon Graphics Inc THE SOFTWARE IS PROVIDED AS IS AND WITHOUT WARRANTY OF ANY KIND EXPRESS IMPLIED OR OTHERWISE INCLUDING WITHOUT LIMITATION ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR ANY SPECIAL INCIDENTAL INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE DATA OR PROFITS WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE AND ON ANY THEORY OF LIABILITY ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE 70 e Technical Support Hemiview User Manual Glossary of Terms Hemiview User Manual analogue Information stored in a continuous form For example photographic negatives and video images which are stored as a voltage wave form are both analogue images See also digital azimuth angle The angle used to measure compass direction Generally azimuth angle is measured relative to true North via East Any sky direction can be represented as a pair of zenith angle azimuth angle co ordinates See also zenith angle bearing Equivalent to azimuth angle degrees A unit used to measure angles There are 360 degrees in a circle Degrees can be converted to radians by multip
79. nd F A Bazzaz 1995 Seedling crown orientation and interception of diffuse radiation in tropical forest gaps Ecology 76 1134 1146 Anderson M C 1964a Light relations of terrestrial plant communities and their measurement Biological Reviews 39 425 486 Anderson M C 1964b Studies of the woodland light climate I The photographic computation of light condition Journal of Ecology 52 27 41 Anderson M C 1964c Studies of the woodland light climate I seasonal variation in the light climate Journal of Ecology 52 643 663 Anderson M C 1970 Interpreting the fraction of solar radiation available in forest Agricultural Meteorology 9 191 216 Anderson M C 1971 Radiation and crop structure pp 77 90 In Z Sestak J Catsky and P G Jarvis eds Plant Photosynthetic Production Manual of Methods Junk The Hague Anderson M C 1981 The geometry of leaf distribution in some south eastern Australian forests Agricultural Meteorology 25 195 205 Andrieu B N Ivanov and P Boissard 1995 Simulation of light interception from a maize canopy model constructed by stereo plotting Agricultural and Forest Meteorology 75 1 3 103 119 Andrieu B Y Sohbi and N Ivanov 1994 A direct method to measure bidirectional gap fraction in vegetation canopies Remote Sensing of Environment 50 1 61 66 Anonymous 1984 Solar energy handbook theory and applications Ametec Incorporated Chilton Book Company Radnor PA Anonymous
80. ng et al 1991 and Chen and Black 1992 as opposed to the projected area which does not work well for all leaf shapes Hemiview algorithms will estimate LAI as half of the total leaf area per unit ground area LAI Models Inversion Models Calculation of LAI involves use of Beer s Law which can be expressed as follows G 8 e K 0 L where G is gap fraction K 0 is the extinction coefficient at angle 0 and L is LAI 0 is zenith angle Tutorial 1 Introduction to Hemispherical Photography e 17 Calculation of LAI involves a kind of iterative inversion model whereby LAI 1s inferred from the observed distribution of gap fraction as a function of zenith angle These models are termed inversion models because they work backwards in that instead of inferring a pattern of gap fraction resulting from a particular distribution of leaves in a canopy they infer the pattern of leaf distribution from the pattern of gap fraction While the former forward model can be solved analytically the latter inverted model requires an iteration of approximate solutions that converge upon a satisfactory solution Assumptions of LAI Models Calculations of LAI assume a random distribution of canopy elements such that gap fraction should be observed for a small enough annulus that randomness can be assumed LAI calculated in this manner is sometimes termed effective LAT LAL since it does not account for non random distribution of
81. ng at North about 1o clock and proceeding anticlockwise The Zenith angle starts in the centre i e up and proceeds out to the horizon at 90 degrees 8 Inspect the SunGap sheet 36 e Tutorial 2 Using HemiView Hemiview User Manual Lo O Bo Eample2 hes The SunGap table shows how much of each sector in the sunmap appears obstructed The sunmap is derived by overlaying a series of solar tracks for the given site The sectors in the sunmap show the suntrack defined by the time of day and time of year Each sector in the sunmap is the area traversed by sun over a half hour period on consecutive days of a month Each cell in the SunGap table corresponds to a sector in the sunmap The values in each cell of the SunGap table derived directly by counting pixels give the proportion of sky visible in that sector where 1 0 represents all the sky is visible and 0 0 represents no visible sky The value 1 in any cell in the results indicates that no meaningful value is available for the cell In the SunGap sheet this occurs for sectors which lie below the horizon The SkyGap and SunGap sheets are special in that they incorporate no models making assumptions about the effects of the atmosphere the amount of radiation or the structure of plants HemiView simply counts pixels and uses site and lens information to apportion the numbers to each sector Next we customise the Calculations Settings Hemiview User Manual Tut
82. nt canopies and in particular forest canopies the same principles apply for many other uses For example hemispherical photography can be used to analyse the influence of human structures such as buildings to analyse the influence of topographic features such as mountains or even to analyse the Tutorial 1 Introduction to Hemispherical Photography e 5 influence of window placement within a room inside a building Applications can be classified into two main categories environmental monitoring modelling and research for agriculture forestry micrometeorology ecology environmental science and remote sensing design and site evaluation for architecture planning and engineering Hemispherical Images as Permanent Records of Sky Visibility and Obstruction Hemispherical photographs provide a permanent record of the geometry of sky visibility and obstruction Hemispherical photographs can be stored as negatives or transparencies and or as digital images Film media have distinct advantages of relatively low cost and high resolution Recent advances in digitisation methodology and storage devices along with decreasing storage media costs now make it practical to create digital archives of hemispherical photographs New technology e g Kodak PhotoCD provides a convenient low cost means for producing digital archives As permanent records hemispherical photographs can be studied using existing analytical methodology and saved for futu
83. o examine and change lens properties Hemiview User Manual Hemiview User Manual Day of Year Toolbar Typical view of the Day of Year toolbar Day pma 21 Apr The Day of Year toolbar allows you to select an active day of year for drawing daytracks and performing time series or sunfleck calculations menu command Settings DayTrack tab Drag the slider or click the up or down buttons or type a Day of Year value directly into the edit box The day is part of the current output configuration so using the Day of Year toolbar modifies the current output configuration Threshold Toolbar Typical view of the Threshold toolbar Threshold 4 22 The Threshold toolbar allows you to decrease or increase the classification threshold for the active image menu command Settings Classifier Alternatively you can click the up or down buttons or type a threshold value directly into the edit box Whenever the active window is an image window you can also use the and shortcut keys to change the threshold Hold down Ctrl and press or to change the threshold in larger steps Solar Models Toolbar Typical view of the Solar Models toolbar Solar Model Simple Model Mole The Solar Models toolbar allows you to select a choice of solar models representing the transmission of solar radiation through the earth s atmosphere These can be edited and inspected in detail via the menu command Settings Solar
84. of year and observe how the position of the daytrack moves across the sky during the course of the year 3 Toggle the View Classified command to show the classified image Observe where the daytrack intersects with visible sky directions These intersections correspond to times when sunflecks will occur 4 Select Settings Output Configuration Properties Click on the Daytrack tab and observe that the Day of Year matches the value in the Day of Year toolbar 5 Set the Time Series Increment to 10 minutes This means that the TimeSer sheet will contain values for every 10 minutes through the day between sunrise and sunset This interval can be reduced to 1 minute which is equivalent to the time it takes for the sun to move half of one diameter 6 Click on the Output Sheets tab and select TimeSer and Sunfleck 7 Close the Calculation Settings dialog and intitiate calculations with the shortcut key 8 Inspect the TimeSer sheet Compare the values in the table to the pattern you see in the image The TimeSer sheet contains the following values e day of year selected for calculation e time in this case at 10 minute intervals e sun s positions zenith and azimuth e visibility of the sun s disc e radiation above and below the canopy both corrected and uncorrected These are instantaneous values for the stated time Tutorial 2 Using HemiView e 45 9 Inspect the Sunfleck sheet The Sunfleck calculation scans the the da
85. ogical amplitudes Oecologia 72 49 459 Wang Y S and D R Miller 1987 Calibration of the hemispherical photographic technique to measure leaf area index distributions in hardwood forests Forest Science 33 210 126 Weiss S B P M Rich D D Murphy W H Calvert and P R Ehrlich 1991 Forest canopy structure at overwintering monarch butterfly sites measurements with hemispherical photography Conservation Biology 5 2 165 175 Welles J M 1990 Some indirect methods of estimating canopy structure Remote Sensing Reviews 5 31 43 Warren Wilson J 1963 Estimation of foliage denseness and foliage angle by inclined point quadrats Aust J Bot 11 95 105 Whitford K R LJ Colquhoun A R G Lang and B M Harper 1995 Measuring leaf area index in a sparse eucalypt forest A comparison of estimates from direct measurement hemispherical photography sunlight transmittance and allometric regression Agricultural and Forest Meteorology 74 237 249 Whitmore T C N D Brown M D Swaine D Kennedy C I Goodwin Bailey and W K Gong 1993 Use of hemispherical photographs in forest ecology Hemiview User Manual Hemiview User Manual Measurement of gap size and radiation totals in a bornean tropical rain forest Journal of Tropical Ecology 9 131 151 Wuensche J N A N Lakso and T L Robinson 1995 Comparison of four methods for estimating total light interception by apple trees of varying forms Hortscience 30 2 2
86. or image classification are various and include the following These are not provided by HemiView modified threshold techniques that produce local thresholds for different portions of an image modified threshold techniques that account for systematic differences in lighting conditions within different parts of the image in particular brighter lighting in the centre as opposed to the edges colour techniques that use colour indices and or advanced lookup table algorithms to classify images Compounding of Errors For hemispherical photography errors can occur at any stage of image acquisition digitisation or analysis Because many steps are involved accumulated error can become great unless strict quality control is exercised A severe error at any stage can invalidate the final results even if other steps are Tutorial 1 Introduction to Hemispherical Photography e 11 performed with little error Strict protocols should be developed and followed to prevent cumulative errors Sources of Error in Hemispherical Photography Camera position horizontal and vertical position film plane levelling azimuth rotation The degree of alignment accuracy required can be quite complicated to predict and depends on the application The following can is intended be used as a rough guide For LAI site factors and global measurements the effect of 1 degree out from level or North alignment are going to be pretty small Cosin
87. orial 2 Using HemiView e 37 Change Calculation Settings 1 Bring up the Output Configurations popup menu by placing the mouse pointer on the Output Configurations toolbar and clicking the right mouse button From the popup menu select New The Calculations Settings dialog appears Calculation Settings x Skymap Intercepting Surface Daytrack Configuration Output Sheets Values Sheet Name ESAE Description fa selection of HemiView outputs and settings chosen for the Tutorial Cancel Help 2 Type in a new name for the output configuration such as MyTutorial 3 Click on the Output Sheets tab 4 Scroll through the output sheet options and select the following Output Sheet What it will display name Overall values calculated for the whole sky or canopy Indirect site o H for each skymap sector corrected for intercepting surface orientation DSF Direct site factor for each sunmap sector corrected for intercepting surface orientation DirBe Direct radiation below the canopy for each sunmap sector corrected for intercepting surface orientation Comments entered by the user 5 Click on Arrange Observe all the selected sheets are now at the top of the list 38 e Tutorial 2 Using HemiView Hemiview User Manual Hemiview User Manual 6 Experiment with changing the output list order by highlighting items in the list and clicking the Up and Down buttons To highligh
88. orientation relative to north should be verified In general it is a good idea to shoot at a shutter speed of 125 1 125 second and adjust the exposure with the aperture ring For this reason shutter speed preferred or non automatic cameras are preferred Generally excellent exposures can be obtained using the internal camera meter Taking Photographs After the camera assembly is properly positioned and the exposure settings are correct photographs can be taken In general photographs should be taken using the camera self timer After the self timer is set the camera assembly should be stabilised until the shutter releases Before the shutter releases fine adjustments to the camera position can be made but such adjustments should be completed well before the shutter releases to ensure that the camera is stable while the photograph is taken Tutorial 3 Field Protocols e 51 Field Records Use of Camera Databacks A camera databack can be used to imprint labels in the corner of each photograph In general it is best to use a mode that prints a unique number on each photograph Most databacks have an auto incrementing number label option Rather than resetting the number label to zero at the start of each roll of film 1t is better to continue to use greater numbers Thus each photograph has a unique number and labelling confusion can be avoided In addition because labels are always imprinted in the same relative position of eac
89. presented Hemispherical Viewsheds Hemispherical photographs provide a hemispherical field of view which when looking directly upwards corresponds to a viewshed of all sky directions This hemispherical viewshed can be represented as an image by projecting the hemisphere of directions on a plane Each position of the image corresponds to a sky direction Sky directions are represented by two angles the zenith angle 6 angle relative to the zenith and the azimuth angle o angle relative to true north As its standard reference HemiView uses an equiangular projection for a full 180 degree field of view Hemispherical Projections The resulting circular image looking upward from beneath the hemisphere shown above gives a complete view of all sky directions with the zenith in the centre of the image and the horizons at the edges Tutorial 1 Introduction to Hemispherical Photography e 7 The hemispherical image above was taken in a treefall gap in the tropical rain forest of Costa Rica Note that north is toward the top of the image south toward the bottom east toward the left and west toward the right East and west are reversed from the usual convention in maps because the view is upward rather than downward Equiangular Projections In an equiangular projection the zenith angle the angle between the zenith and a given sky location is directly proportional to the distance along a radial axis within the image 9
90. r diffuse solar radiation transmitted from visible sky directions as opposed to reflected radiation from surfaces in obscured sky directions Direct radiation for a particular site depends upon the relative position of the sun as it changes through the day and through the year as well as upon atmospheric conditions Diffuse radiation for a particular site depends upon the amount of incoming radiation that scatters from each sky direction For any given period of time global radiation reaching a location under a plant canopy is defined within Hemi View as the sum of direct and diffuse radiation entering through canopy openings and does not include reflected radiation off of surfaces in obscured sky directions Analyses of hemispherical photographs commonly use indices expressed as the proportion of direct or diffuse solar radiation for a given location relative to that in the open known as direct and diffuse site factors respectively The Basic Model for Estimation of Solar Radiation A reasonable estimate of radiation from direct radiation can be obtained by looking at the intersection between visible sky directions and the amount of direct radiation that can be expected from those sky directions Similarly a reasonable estimate of radiation from diffuse radiation can be obtained by looking at the intersection between visible sky directions and the amount of diffuse radiation that can be expected from those sky directions Tutorial 1 Introd
91. r the pixel when classified represents obscured OBS or visible VIS or ignored IGN sky Display the Sunmap and move the pointer over it e Ifthe pointer is over over a section of the sky covered by the sunmap then a date and time is displayed representing the time of year when the sun would appear at that location Of the two times in the year when the sun will appear at each location the date and time is shown for the half year which contains the day of year shown in the Day of Year toolbar _ _ 2 xY 409 432 AZ 184 8 65 4 AGB 27 25 27 085 14Feb1218 4 Next we need to align the image Tutorial 2 Using HemiView e 25 Align Image 26 e Tutorial 2 Using HemiView It is necessary to align the image with the hemispherical co ordinate system so that HemiView knows where to find North and the horizon This is all needed for the calculations The alignment overlay shows the location and geographic orientation of the horizon circle 1 Turn the alignment overlay on There are several ways of doing this e Press the A shortcut key e Right click on the image and left click on Alignment in the pop up menu e Click on the toolbar button m e Select the View Alignment command Alignment overlay as it might appear before aligning It shows the horizon circle with the four cardinal points N S E amp W and the magnetic North symbol next to the pointer at about 10 o clock The LEDs a
92. ras present the possibilities to combine acquisition and digitisation in one step A primary challenge in image acquisitions is to obtain high contrast images with excellent distinction between visible sky and obscured sky directions Another challenge is to ensure that the camera is properly oriented such that the axis of the lens is pointed directly upward and the camera is oriented with magnetic north in a known direction See 10 e Tutorial 1 Introduction to Hemispherical Photography Hemiview User Manual Hemiview User Manual Tutorial 3 Field Protocols on page 47 Classification of Images Classification of images involves using digital image processing to distinguish visible and obscured sky directions In the case of plant canopies this means distinguishing canopy opening from foliage Threshold Method Use of a threshold algorithm is one of the simplest and most effective means for classifying an image Classification is achieved by determining a threshold intensity value above which is classified as visible and below which is classified as obscured This technique is also known as segmenting an image in that it divides a set of grey levels intensity values into a binary classification The technique has the advantage that it is relatively simple to understand and use but has problems that can result because of unevenness in the light conditions within images Successful classification depends upon having high cont
93. rast photographs in which foliage or other sky obstruction is consistently darker than visible sky directions Problems arise if parts of the visible sky are darker than obscured sky directions for example dark clouds or if parts of the obscured directions are brighter than the visible sky for example reflections on leaves In practice for canopies the technique involves a compromise between overestimating large areas of visible sky large canopy openings near the zenith and underestimating small areas of visible sky small canopy openings near the horizon Within reason images can be edited to compensate for dark sky regions or bright obscured regions using commercial image editing software such as the Paint program provided with Windows 95 This typically involves manually changing values for regions of an image and using flood routines to assist in classifying problematic portions of images In Hemi View thresholds are determined interactively such that a user can instantaneously toggle back and forth between the threshold display and a continuous tone display while increasing or decreasing the threshold value until edges of the classified image best match visible or obscured sky edges of the continuous tone image Subjectivity in the choice of thresholds is minimised by adopting strict protocols for deciding thresholds by practice and by use of high contrast images taken under even lighting conditions Other Methods Other methods f
94. re clearly visible at 12 and 6 o clock The digits at bottom right added by the camera can be very useful for identifying pictures The actual horizon is defined as a circle at the 90 degree zenith angle The alignment overlay shows a horizon circle marked with the four compass directions N E S amp W and a compass needle indicating magnetic north Note that East is to the left of North and West to the right in hemispherical photographs since they are taken looking upward If you cannot see the alignment overlay it may simply be the wrong colour To change the colour of the horizon circle a Select the menu command Settings Appearance b Inthe Appearance tab click on Alignment c In the Color dialog select a bright colour such as yellow d Click OK to return from the Color dialog to the Alignment tab and OK again to return to the image 2 Move the mouse pointer around the circle and observe how the symbol changes Hemiview User Manual Hemiview User Manual Every 45 degrees from the top of the circle the pointer becomes a double headed arrow pointing towards and away from the centre of the circle This indicates that you can now resize the horizon circle 3 Hold down the left mouse button and drag the horizon circle to the required size In between the pointer becomes a 4 headed arrow symbol indicating you can move the circle by dragging Immediately outside the horizon circle on the compass needle and on the N E
95. re study Analogous to the way voucher specimens are collected for vegetation or floristic studies hemispherical photographs can be collected and archived for comparative study of plant canopies Brief History of Hemispherical Photography Hill 1924 first designed the hemispherical fisheye lens for view of the whole sky to study cloud formation Later architects used hemispherical photographs to assess site factors that estimate the solar radiation regimes at different positions within or near buildings Foresters and forest ecologists conceived of using photographic techniques to study the light environment under forest canopies In particular Evans and Coombe 1959 estimated solar radiation penetration through forest canopy openings by overlaying diagrams of the sun track on hemispherical photographs Anderson 1964 1971 provided a thorough theoretical treatment for calculating the penetration of solar beam direct and scattered diffuse or indirect components of solar radiation from visible sky directions as determined using hemispherical photographs In recent years many researchers have successfully used hemispherical photography to study solar radiation regimes and plant canopy architecture see reviews in Chazdon and Field 1987 Rich 1988 1989 Becker et al 1989 Detailed treatments of field and analytical methodology have been provided by Pearcy 1989 and Rich 1989 Until relatively recently interpretation of hemisp
96. reaching a given location relative to that in a location with no sky obstructions Global site factor GSF is the proportion of global radiation direct plus diffuse under a plant canopy relative to that in the open total site factor of Anderson 1964 ISF and DSF can readily be estimated from canopy photographs given assumptions about the contribution of diffuse and direct radiation from each sky sector GSF can be estimated if we have an estimate of the relative proportions of diffuse and direct radiation in the open either determined empirically or theoretically Converting Site Factors to Energy Flux PFD or PPFD ISF DSF and GSF can be considered to be proportional estimates of energy flux PFD for total radiation or PPFD and can be translated to absolute levels of radiation flux for a particular period of time by multiplying by the appropriate radiation values measured in the open for the site Leaf Area Index from Hemispherical Photographs What is Leaf Area Index Leaf area index LAD is widely used to describe the photosynthetic and transpirational surface of plant canopies LAI can be simply defined as the amount of leaf surface area per unit ground area and has broad applications in ecophysiology water balance modelling and characterisation of vegetation atmosphere interactions In recent years many researchers have adopted the definition of LAI as half of the total leaf area per unit ground surface area La
97. reater in sites that were defoliated as compared with sites that were not heavily impacted By 33 months most site differences had disappeared Hemispherical photography represents an effective method for examination of temporal patterns of change Hemispherical photographs can be used to study variation in solar radiation over small space and time scales In particular various studies have focused on sunflecks as they influence ecophysiology and growth Calculation of sunfleck regimes can be more challenging than calculation of integrated measures of solar radiation because the exact timing and duration of sunflecks is related to accurate alignment and image classification While accurate alignment and image classification are always of importance when using hemispherical photography these considerations are of even greater concern when small differences in timing or duration may affect results Typically sunfleck studies focus on an individual plant or a single leaf When focusing on a single planar leaf it is most appropriate to perform a calculation for a double sided surface of interception This enables accounting for solar radiation that intercepted by either side of the leaf surface Using sunfleck regimes as an input to ecophysiological models of plants Pearcy R W and W Yang 1996 A three dimensional crown architecture model for assessment of light capture and carbon gain by understory plants Oecologia 108 1 12 This study used
98. ree vectorization and 2 mapping the size diameter and height of trees simulated within the stand There was a strong correspondence between simulated and empirical hemispherical photographs Recording and analysing structure Hemispherical photographs can be used to calculate various indices concerning the physical structure of plant canopies canopy architecture LAI is the most common index Associated with LAI are such measures as mean tip angle MTA Comparison of leaf area index of forest stands Chen J M P M Rich S T Gower J M Norman and S Plummer 1997 Leaf area index of boreal forests theory techniques and measurements Journal of Geophysical Research BOREAS Special Issue 102 D24 29429 29444 In recent years various studies have begun to provide comparative data concerning LAI This study reviews LAI calculation theory and compares four methods for field measurement of LAI TRAC LAI 2000 sunfleck ceptometer and hemispherical photography All of the instruments underestimate LAI of boreal forest stands because of clumping of foliage Foliage clumping coefficients were determined using a video camera and rotational light table system Surface area of conifer shoots was measured using a volume displacement method Hemispherical photography was observed to have the advantage of providing a permanent record of canopy geometry Challenges and Opportunities HemiView is a powerful tool that can be used in many ways
99. relations of fisheye photography to canopy structure light climate and biological responses to light in apple trees Journal of the American Society of Horticultural Science 105 43 46 Leong W R Lemeur and P K Yoon 1982 Characterisation of leaf area index and light penetration of Hevea brasiliensis Muell Arg by hemispherical photography Journal of the Rubber Research Institute of Malaysia 30 80 90 Lerdau M T Holbrook N M H A Mooney P M Rich and J L Whitbeck 1992 Seasonal patterns of acid fluctuations and resource storage in the arborescent cactus Opuntia excelsa in relation to light availability and size Oecologia 92 166 171 Lin T P M Rich D A Heisler and F J Barnes 1992 Influences of canopy geometry on near ground solar radiation and water balances of pinyon juniper and ponderosa pine woodlands American Society for Photogrammetry and Remote Sensing Technical Papers pp 285 294 Lindroth A and K Perttu 1981 Simple calculation of extinction coefficient of forest stands Agricultural Meteorology 25 97 110 List R J 1971 Smithsonian meteorological tables Sixth revised edition Smithsonian Miscellaneous Collections Volume 114 Smithsonian Institution Press Washington Madgwick H A I and G L Brumfield 1969 The use of hemispherical photographs to assess light climate in the forest Journal of Ecology 57 537 542 Miller J B 1967 A formula for average foliage density Australian Journal o
100. rest at large whereas five species of nonpioneer shade tolerant species occurred in microsites with solar radiation levels below that of the forest at large Two dimensional maps of solar radiation from arrays of photographs multiple transects Galo A T P M Rich and J J Ewel 1992 Effects of forest edges on the solar radiation regime in a series of reconstructed tropical ecosystems American Society for Photogrammetry and Remote Sensing Technical Papers pp 98 108 By acquiring hemispherical photographs in arrays it is possible to produce two dimensional maps This study used hemispherical photographs taken in a series of fifteen transects from the forest edge into an eight hectare clearing to produce maps of direct radiation ISF monthly DSF and hours of direct beam radiation were calculated from the photographs In general east and west forest edges modify daily regimes of solar radiation while north forest edges modify seasonal regimes south edges in the southern hemisphere and both north and south edges within the tropics As a rule of thumb the influence of the forest edge was strongest up to a distance approximately equal to the canopy height 30 to 40 m in this case Isoline maps of the duration of direct beam radiation were derived for the summer solstice equinox and winter solstice Based on these Hemiview User Manual Sunfleck studies Hemiview User Manual maps it was possible to assess the influence of the
101. ridge and O Rackham eds Light as an ecological factor II Blackwell Oxford Evans G D and D E Coombe 1959 Hemispherical and woodland canopy photography and the light climate Journal of Ecology 47 103 113 Field C B 1988 On the role of photosynthetic responses in constraining the habitat distribution of rainforest plants Australian Journal of Plant Physiology 15 343 358 Fournier R A R Landry N M August G Fedosejevs and R P Gauthier 1996 Modelling light obstruction in three conifer forests using hemispherical photography and fine tree architecture Agricultural and Forest Meteorology 82 47 72 Fournier R A P M Rich and R Landry 1997 Hierarchical characterisation of canopy architecture for boreal forest Journal of Geophysical Research BOREAS Special Issue 102 D24 29445 29454 Fournier R A P M Rich Y R Alger V L Peterson R Landry and N M August 1995 Canopy architecture of boreal forests links between remote Hemiview User Manual Hemiview User Manual sensing and ecology American Society for Photogrammetry and Remote Sensing Technical Papers 2 225 235 Galo A T P M Rich and J J Ewel 1992 Effects of forest edges on the solar radiation regime in a series of reconstructed tropical ecosystems American Society for Photogrammetry and Remote Sensing Technical Papers pp 98 108 Gates D M 1980 Biophysical ecology Springer Verlag New York Genard M and F Baret 1994 Spat
102. rm overcast sky Hemiview User Manual In a uniform diffuse distribution sometimes referred to as a uniform overcast sky or UOC incoming diffuse radiation is the same from all sky directions In this case the diffuse radiation is proportional to the angular area of a sky sector See also standard overcast sky viewshed The directions that are visible from a given location zenith angle The angle used to measure sky direction or inclination relative to the zenith Any sky direction can be represented as a pair of zenith angle azimuth angle co ordinates See also azimuth angle Hemiview User Manual Glossary of Terms e 75 Index A algorithms 11 17 59 Align Image 26 Altitude 31 Angle of Incidence 16 Appearance tab 26 Archiving 3 53 AZ 25 B blue filter 51 butterflies 55 63 C Calculate 22 34 41 45 59 Calculate 18 Calculations Theory 36 Camera Positioning 48 51 Camera Positioning and Orientation 51 cameras 10 12 47 51 Centre XY 27 Centroid 16 checklist 51 Classified 11 22 24 32 41 Classifier Settings 33 Classify Image 32 clumping factor 18 Coefficients 58 61 Comment 35 Comments Sheet 41 Converting Site Factors to Energy Flux PFD or PPFD 17 Coolpix camera 28 Co ordinate 7 9 12 25 COPYRIGHT 21 70 CREDITS 70 cursor 25 D Databacks 52 DATE 25 31 52 68 Hemiview User Manual Day of Year toolbar 23 30 45 daytrack overlay 22 29 Delta T contact 68
103. rowns can be used to estimate solar radiation regimes or site indices from the perspective of and individual and in turn related to physiological or ecological measurements This study examined relations between solar radiation regimes above saplings gas exchange carbon uptake and annual growth for three species of tropical trees with different life histories Measurements of annual growth were correlated with indices of both direct and diffuse radiation expressed as ISF and DSF and with the strongest relationship with ISF Site factors as they relate to habitat suitability for animal species Weiss S B P M Rich D D Murphy W H Calvert and P R Ehrlich 1991 Forest canopy structure at overwintering monarch butterfly sites measurements with hemispherical photography Conservation Biology 5 2 165 175 Hemispherical photographs can also be used to characterise habitat for animal species This study examined site factors indirect and direct site factors as they relate to suitability of different stands as overwintering sites for monarch butterflies Suitable habitat corresponded to a limited range of ISF and DSF that relates to the physiology of the butterflies Sites with too much solar radiation would cause butterfly metabolism to increase and deplete fat reserves while too little solar radiation would cause metabolism to be so low that butterflies would not become active at the appropriate time for migration in the spring The
104. s ista ad 22 Lens Last Toolbar iia 22 Day of Year Tool a caida 23 Threshold Toolbar dida etna 23 Solar Models Toolbar cccciooconcnico canino tasriaidancar carne a caen 23 Output Configuration Toolbar ooonoconncnononononononononononn nono nnnn cono c nono nooo nn cnn con ccoo cnn 23 Open an Image coi li Do ia 24 Align Mai odia a ii dona 26 Overlay Skymap Sunmap and Daytrack ooooonocccononononononononononnncnncnnnnnnnonnnc nn cnn nono nonanannnnnos 29 Hemiview User Manual Contents e ET Ee Lo T ATE A NET E E EEE EE E E AEE 30 Site Properties esitin eE sees a E E a E oE E E AE EEEE Er EEEE E Ee 31 Solar Modelis a IL a ests 31 Classify Ma E nn aa nase E A eden a ete I ASNS 32 Inspect Results iii ais 34 Change Calculation Settings 0 0 eee eecseesceseceseceecssecssecsaecseecaeecseseaeseeecaeseseseaeeeeeeeees 38 Uncorrected U as in DSFU does not mean horizontal surface 40 Calculate Results cui piano ita 41 Using hvs HemiView Settings Files oooooniononcnocnconncononononnncnn non nonononnnrnn crac conc cnnncnonnnonns 43 Learn about hvs HemiView Settings files ooononccnnoccconcconoccconononnncconcconnncnnnoss 43 Next time you Open an image eee cee csecseeereeeeeeeeeeeeeeeseesecssecaecaeeaeeaeeees 43 Calculating Time Series and Sunfleck Duration 00 0 elie eseeeeeeeeeeeeeeeeeeseeeeenseeeees 45 Tutorial 3 Field Protocols 47 Goal of Photograph AcquISItiOM ooooonoccnoncnonconnconnconoconocnocn
105. s to be displayed or hidden A check mark or tick appears next to each toolbar that is displayed Standard Toolbar Contains buttons for file management editing printing and help New create a new workbook menu command File New Open an existing workbook or image HemiView displays the Open dialog box in which you can locate and open the desired file menu command File Open y E Save the active image or workbook with its current name If you have not named the document HemiView displays the Save As dialog box menu command File Save a Cut highlighted cells from the workbook and store it on the clipboard menu command Edit Cut Copy the image or highlighted workbook cells to the clipboard menu command Edit Copy Paste the contents of the clipboard into a workbook at the insertion point menu command Edit Paste Print the active workbook or image menu command File Print About HemiView Displays version number your serial number license and copyright information What s This Displays context sensitive help about the program area under the mouse when you click the left mouse button Eee a la Es View Toolbar Contains buttons for controlling the display of images Tutorial 2 Using HemiView e 21 22 e Tutorial 2 Using HemiView Toggle the displayed Image on and off menu command View Show Image Toggle between Negative and normal images display menu command View Negative
106. sample measurements that are possible as compared with direct solar radiation sensor measurements or direct leaf area measurements Computer analysis with HemiView involving advanced digital image analysis techniques enables efficient analysis of large numbers of photographs Hemispherical Photography as Upside Down Remote Sensing Hemispherical photography can be thought of as upside down remote sensing Hemispherical photographs can be analysed by hand or automated digital image analysis to precisely measure geometry and its implications Once properly classified hemispherical photographs literally provide a detailed map of sky visibility and obstruction In turn solar radiation regimes and canopy characteristics can be inferred from this map of sky geometry In the case of plant canopies a hemispherical photograph can be interpreted as a map of the directions of canopy openings relative to the location from which the photograph is taken They can be inspected to provide insight into heterogeneity within a given canopy and to compare canopies at different sites Some Applications of Hemispherical Photography Herein the term hemispherical photograph is used to refer to any extremely wide angle upward looking image generally with a 180 degree field of view whether it is obtained from a film camera a digital camera or from a theoretical model While this manual tends to emphasise using hemispherical photography to analyse pla
107. sector where a sky sector is defined by a range of zenith and azimuth angles All calculations whether for solar radiation regimes or for canopy characterisation ultimately depend upon dividing the sky into sectors and calculating gap fraction for each sky sector A gap fraction of zero 0 means that the sky is completely blocked obscured in that sky sector A gap fraction of one 1 means that the sky is completely visible not obscured in that sky sector Gap Fraction for the Sunmap Gap fraction along the path of the sun is derived by overlaying a series of solar tracks to produce a Sunmap of sky sectors defined by time of day and day of year and calculating the proportion of sky visible in each sky sector Gap Fraction for the Skymap Gap fraction for any sky direction is derived by overlaying a grid of sky sectors defined by zenith and azimuth angle ranges to produce a Skymap and calculating the proportion of sky visible in each sky sector What do the Skymap and Sunmap represent 14 e Tutorial 1 Introduction to Hemispherical Photography Hemiview User Manual Hemiview User Manual Although the Sunmap and Skymap are similar overlays they have some important differences when used by Hemiview especially for calculating radiation values The Skymap divides the hemiphoto into areas representing different directions so shows variations in space When combined with the inci
108. t an item without unchecking it click on the text of the item not the check box Hold down Shift or Ctrl keys to highlight multiple items within the list 7 Click on the Values Sheet tab and in addition to the defaults offered add TotBe 8 Click on the Skymap tab and ensure that the number of Azimuth divisions 1s set to 9 and the number of Zenith dvisions is set to 18 9 Click on and inspect the Intercepting Surface tab HemiView allows you the choice of calculating what radiation would be received on a perfectly absorbing flat surface or aperture oriented at any angle The tilt of a surface can be conveniently described by the zenith and azimuth angles of a normal or perpendicular line to the surface Azimuth The angle in degrees for the normal to the intercepting surface 0 North 90 East 180 South 270 West Zenith The zenith angle in degrees for the normal to the intercepting surface 0 horizontal 90 vertical 10 We wish to perform a calculation that includes solar radiation interception by a horizontal surface so set the zenith angle to O the azimuth angle is immaterial or undefined in this instance Note that calculations for non horizontal surfaces can be useful for calculating solar radiation interception by leaves in different orientation and for calculating solar radiation interception for non horizontal slopes Tutorial 2 Using HemiView e 39 11 Select Sing
109. t of an image in its associated hvs file Hemiview User Manual Overlay Skymap Sunmap and Daytrack HemiView can overlay various types of graphics on hemispherical images including the alignment overlay skymap overlay sunmap overlay and daytrack overlay El E The skymap left covers the whole sky The sunmap right covers the path of the sun through the whole year the alignment overlay is also shown The daytrack overlay not displayed here shows the path of the sun on one day These overlays are useful for examining patterns in the images for example how the sunmap coincides with canopy openings In addition HemiView allows you to display e negative images as positives e overlays without images e classified images Overlays are useful when producing illustrations which can then be copied and pasted in other applications or printed All overlays shown 1 Select View Negative Observe that a negative of the image is displayed Uncheck the negative mode and observe that the display changes back to a positive display Hemiview User Manual Tutorial 2 Using HemiView e 29 F El d Day 2 ao 31 Mar Lens Selection Lene Linear 180 a 30 e Tutorial 2 Using HemiView 2 Select View Alignment Observe that this choice toggles off the alignment overlay Turning this off can be useful when producing graphical illustrations Toggle th
110. te The HemiView lens equations are expressed in radians not degrees Zenith Angle degrees 0 0 02 0 4 O 8 D B 1 0 Propartian of Radial Distance Why Hemispherical Photographs Represent Angles Not Distance Simply stated each position in a hemispherical photograph represents a direction from the location where the photograph was acquired Each position corresponds to a zenith azimuth angle co ordinate in a hemispherical co ordinate system Actual distance such as heights of trees or diameters of treefall gaps can only be calculated if additional information is available such as the height of the canopy Distance in a hemispherical photograph corresponds to angles not to actual distance Within a photograph the radial component of distance is proportional to zenith angle and the distance in an arc at a fixed radius is proportional to azimuth angle Area in a hemispherical photograph corresponds to angular area or along a hemisphere of directions With supplementary measures of distance or hemispherical photographs taken at known distances from each other it is possible to determine distances using Tutorial 1 Introduction to Hemispherical Photography e 9 standard trigonometry Note how two canopies of different heights can have similar angles of openings as shown below Basic Steps of Hemispherical Photography The three basic steps of digital image analysis of hemispherical photography are image acquisition digitisation
111. ting surface can be set to any orientation It would typically be set to horizontal Zenith 0 Azimuth 0 to give results comparable to measurements made with levelled cosine corrected sensors However there are cases e g modelling the response of individual leaves where 1t is appropriate to set the intercepting surface to the same orientation as the surface being studied What are the Units of Solar Radiation Solar radiation flux can be variously expressed in terms of energy flux or in terms of Photon Flux Density PFD Energy flux is commonly measured in units of megajoules per square meter per second MJm 3s7 PFD is commonly measured in micromoles per square meter per second umol msec These are also known as microEinsteins UE PAR and Other Wavelengths of Interest For study of energy balance it is common to study all wavelengths of solar radiation termed total radiation For study of plant ecophysiology especially when studying processes of light interception for photosynthesis it is useful to measure photosynthetically active radiation PAR those wavelengths that are active in photosynthesis 400 700 nm PAR flux is referred to as photosynthetic photon flux density PPFD Site Specific Solar Radiation Values Considerable variation in solar radiation regimes occurs between sites even at the same latitude Further energy flux PFD for total radiation and PPFD are not always linearly proportional Site spec
112. tive to that outside the canopy whereas the diffuse and direct radiation values are expressed in solar radiation units 5 Examine the SkyGap and SunGap tables to see if you can identify the effects of openings in the canopy Tutorial 2 Using HemiView e 41 42 e Tutorial 2 Using HemiView 6 Click the Image Workbook toolbar button a to switch quickly between image and workbook windows 7 Click on the image and press the minus shortcut key several times until you can see the difference on the image 8 Click Ea to recalculate and inspect the results Observe that the new results are appended below the previous ones and that each output sheet has scrolled down so as to display the most recent set of results 9 Observe on the Image sheet that your selected threshold setting has been recorded for each calculation 10 With the results workbook active select the File Save AS command and save the workbook to the file tutorial xls in your working directory That s it Next we look at file handling Hemiview User Manual Using hvs HemiView Settings Files Hemiview User Manual Previous sections of Tutorial 2 covered opening aligning and classifying the image and displaying and saving results HemiView allows you to save alignment and classification information together with the lens and site names and the name of the original image file in a hvs or HemiView Settings file Information about whether the i
113. to precisely distinguish foliage from canopy openings using a threshold technique Bright reflections on leaves can be mistaken for openings Whenever possible photographs should only be taken when the sky is overcast because sky lighting conditions play such a significant role in determining photograph quality Permanent Photograph Sites Establishment of permanent photograph sites enables one to take repeated photographs of the same canopy through time Such time records enable documentation of seasonal changes in canopy openness and light penetration and also enable monitoring of directional changes in canopies for instance formation or closure of treefall gaps For such work it is important to position and orient the camera in exactly the same way each time a photograph is taken One means for exact positioning involves setting up permanent posts with a pin registered platform that directly supports the camera mount Special Methodology for the Humid Tropics 52 e Tutorial 3 Field Protocols The humid tropics can be a difficult environment for hemispherical canopy photography primarily because the high humidity is very rough on field Hemiview User Manual Film Processing equipment High humidity can cause camera electronics and mechanical components to malfunction and cause fungus to grow between lens elements For this reason the camera and lens should be stored in a dry box or air conditioned environment when not in use
114. trates the canopy An intercepted direct site factor IDSF can be calculated as 1 DSF and an intercepted indirect site factor IISF can be calculated as 1 ISF The perspective of interception is especially common for studies that with to examine function of the canopy as a whole in terms of considerations such as carbon uptake transpiration energy balance or ecological implications Many of the studies placed in the Solar radiation regimes below the canopy could equally well be placed here Solar radiation interception in forest canopies as it relates to succession Canham C D A C Finzi S W Pacala and D H Burbank 1994 Causes and consequences of resource heterogeneity in forests interspecific variation in light transmission by canopy trees Canadian Journal or Forest Research 24 337 349 Solar radiation intercepted by the canopy is potentially available for growth of the individual plants that intercept the radiation and made unavailable for individuals growing beneath This study examined the influence of interception and transmission characteristics of crowns on succession in temperate deciduous forest Hemispherical photographs where used to gather species specific light extinction coefficients by using maximum likelihood techniques along with detailed measurements of the identity location and geometry of trees in the neighborhood of each photography Later successional shade tolerant trees cast the deepest shadows
115. ts Alternatively you may prefer to select Energy in Watts m 4 Select the Solar Transmission tab and observe that the simple transmittance model requires three values a transmittivity value the amount of direct beam transmitted through unit atmospheric depth typically between 0 4 and 0 9 a proportion of external solar flux scattered as diffuse radiation typically between 0 1 and 0 6 and a value for the external solar radiation flux incident on the outside of the atmosphere also known as the solar constant The currently accepted value is 1370 Wm 5 Select the Diffuse Distribution tab and observe that you can choose between a Standard Overcast Sky model and a Uniform Overcast Sky model These describe the pattern of diffuse illumination from a clear sky not actually overcast 6 Select the Uniform Overcast Sky UOC model which assumes that equal amounts of diffuse radiation originate from all sky directions Click OK See also The Basic Model for Estimation of Solar Radiation on page 15 HemiView needs your help deciding which part of the sky is visible and which is obscured We call this classifying the image Hemi View uses the total intensity ie the sum of the red green and blue values of each pixel to determine whether it should be counted as obstructed or visible sky Pixels which are brighter than a Threshold intensity value are counted as visible Darker pixels are counted as obstructed Your job
116. uction to Hemispherical Photography e 15 In this basic model as viewed from beneath a plant canopy foliage absolutely blocks incoming radiation and canopy openings allow radiation to pass unimpeded Radiation reflected by or transmitted through foliage is ignored Direct radiation is calculated by multiplying the gap fraction of a sunmap sector by the radiation originating from that sky sector and correcting for angle of incidence Similarly diffuse radiation is calculated by multiplying the gap fraction of a skymap sector by the radiation originating from that sky sector and correcting for the angle of incidence What is Angle of Incidence The angle of incidence is the angle between a surface and incoming radiation reaching the surface measured relative to the direction normal to the surface The amount of radiation reaching the surface is proportional to the cosine of the angle of incidence Thus radiation originating at a right angle to the surface has an angle of incidence equal to zero a cosine of one and receives the full amount of radiation whereas radiation originating parallel to a surface has an angle of incidence of 90 degrees a cosine of zero and receives no radiation from that direction HemiView accounts for angle of incidence by multiplying radiation originating from each sky sector diffuse or direct by the cosine of the angle of incidence from the centroid of the sky sector to the surface Within HemiView the intercep
117. uivalent to 14 7 KJ m 2 day 1 The percentage of solar radiation which reaches the ground and shows up in net primary productivity is thus about 0 086 radians A unit used to measure angles There are 2 PI radians in a circle Radians can be converted to degrees by multiplying by 180 PI See also degrees solar constant The amount of solar radiation incident above the atmosphere solar radiation The electromagnetic radiation received from the sun at the surface of the Earth Solar radiation lies almost entirely in the wavelength band of 0 29 4 um and is often called shortwave radiation The amount of solar energy beyond 2 5 um is very small standard overcast sky In an standard overcast sky distribution SOC diffuse radiation flux varies with zenith angle according to the following relation from Moon and Spencer 1942 Le Lz 3 1 2 cos where 6 is the zenith angle Lg is the luminance radiation flux from a given sky direction and Lz is the luminance at the zenith See also uniform overcast sky transmitivity Transmitivity is the percentage of the solar radiation incident on the atmosphere that is transmitted in the direct beam through the atmosphere from the zenith to sea level That is the percentage transmitted though a unit atmosphere depth transpiration Transpiration is the process by which water moves by diffusion from the inner leaf surfaces through stomatal pores to the outside air unifo
118. velling mount Unfortunately in this picture both LEDs look the same so it is impossible to figure out which one is North Tutorial 2 Using HemiView e 27 28 e Tutorial 2 Using HemiView For the purposes of the tutorial we will assume that the LED at 12 o clock was oriented towards Magnetic North with a compass For future reference if you have two identical LEDs on your camera do not remove the south light because it helps define the horizon circle Instead change the shape in some way for instance by wrapping a wire around it or using a dab of paint or carefully filing it Note North is indicated by the triangular shaped light source on digital photos created using the Delta T self levelling mount for the Nikon Coolpix camera 9 Rotate the image dragging the triangular compass indicator around to the light at 12 o clock When aligning images you may find it helpful to use magnify the image using the View Zoom command and to split the Window into two using theWindow Split command as shown below 10 Adjust the size and location of the circle so that it is centred correctly marks the horizon and is correctly oriented to the compass directions The angle between magnetic and true North the magnetic declination is a property of the site selected for the image and is defined via the Settings Site Properties command We will come to this later in the tutorial Hemi View stores information about the alignmen
119. ways added below previous results 5 Click OK in the Calculate dialog An Excel 5 0 compatible workbook will appear containing several worksheets of results as shown below hos TT lt el The Summary Comments and Image sheet contain input information ie information which you the user has provided as inputs to HemiView s calculations Click on each in turn and inspect them In this example the first sheet with results in is the fourth tab along the Values sheet 6 Click on the Values tab Sample2 hvs 0 177 0 242 0 232 Ma al Comments A Image A Values Tutorial 2 Using HemiView e 35 Results in the Values sheet reflect the whole canopy or the whole image In general most entries in the Values sheet represent a summation over all positions in the sky or over time In contrast most of the other sheets are tabulated according to position in the sky or by time The abbreviation ISF stands for Indirect Site Factor the proportion of diffuse solar radiation reaching a given location relative to a location with no sky obstructions Values range from 0 to 1 with 0 representing complete sky obstruction and 1 representing open sky To find out definitions see the Appendices Calculations Theory section in the on line Help and Glossary of Terms In the Glossary of Terms you will find the following definition Global Site Factor GSF The proportion of global ra
120. while earlier successional less shade tolerant trees allowed greater transmission The study is consistent with models that explain secondary succession as a process driven by interspecific differences in resource uptake and tolerance Solar radiation uptake interception restricts growth to later successional species that are tolerant able to growth in their shade Solar radiation interception in three dimensional reconstructions of forest canopies Fournier R A P M Rich and R Landry 1997 Hierarchical characterisation of canopy architecture for boreal forest Journal of Geophysical Research BOREAS Special Issue 102 D24 29445 29454 Reconstruction of the three dimensional geometry of forest canopies is practical using modern computers but challenging because of the difficulty of obtaining data concerning the distribution of canopy elements Once a three dimensional construction is available it can be used to simulate solar radiation interception regimes beneath the canopy and relations between canopy properties and observed structure from beneath This study presents a hierarchical methodology for reconstruction of the three dimensional geometry of forest stands and compares simulated versus empirical hemispherical views of a forest stand The three dimensional geometry of individual trees is reconstructed based Hemiview User Manual on 1 sub sampling of branch and leaf elements to enable simulation of individual trees t
121. ystem Introduction e 1 2 e Introduction Interactive image classification allows the user to adjust a threshold intensity value that distinguishes visible sky from sky obstructions producing a classified image The user can toggle instantaneously between a full colour display of the canopy photograph and a threshold display of the classified image Rapid calculations are made possible by HemiView s use of advanced algorithms to calculate gap fraction contributions of direct and diffuse solar radiation from each sky direction site factors and leaf area index LAI Computation and results output generally require less than one minute on a Pentium computer Typically each image can be analysed in two to five minutes including all steps of input alignment selection of a threshold calculation and output of results The results of analysis are output to a fully functional spreadsheet where they can be further analysed within the HemiView environment Alternatively the spreadsheet can be saved to disk as an Excel 5 0 compatible workbook for archiving or further analysis A large selection of options for calculated results permits users to custom design output suited to particular needs HemiView is fully configurable such that a user can specify detailed site and lens characteristics for use in calculations Hemiview User Manual Install HemiView System Requirements Hemiview User Manual HemiView runs on 486 and Pentium
122. ytrack from sunrise to sunset at 30 second intervals i e at a resolution of one quarter of a solar diameter The sunfleck calculation gives the start and stop times of any sunfleck and the amount of radiation during that sunfleck The Sunfleck sheet contains the following values e day of year selected for calculation e start and stop times of each sunfleck e maximum peak radiation value during the sunfleck e integrated radiation values over the whole of the sunfleck Inspect the classified image and confirm that the calculated sunflecks coincide with intersections of the daytrack with visible sky regions 46 e Tutorial 2 Using HemiView Hemiview User Manual Tutorial 3 Field Protocols Goal of Photograph Acquisition Camera System When acquiring hemispherical canopy photographs in the field the basic goal is to obtain high quality photographs Photograph quality is critical Poor quality photographs are difficult to analyse and can produce ambiguous results Good quality photographs result when sufficient care is taken to position level and orient the camera correctly when the exposure is correct when the sky lighting is very even and when there are no bright reflections High contrast images with even sky lighting are difficult to obtain and represent the primary weakness of the technique In general it is best to take photographs under conditions with even back lighting in particular just before dawn or just after sunset

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