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ACORN 4 Tutorial

1. c Program Files ACORNA Dates Jaspernjspblmrt Qa Mode 6 Specio Paremeters Image Spectral Response File wv nm response C Program FilesvACORHNA Dele Jespertm rep Image Torget Raflectonce values File volue C Program Filas ACORN Data Jesper jepiim ext Meesured Target Reflectance File C Program Files ACORN4 Data Josperijspiim mens dtr if Figure 9 4 ACORN Mode 6 control file parameter entry window Input Image File Name This is the name of the input radiance image file The default location is C Program Files ACORN4 Data jasper jsp5tmrfl Output Reflectance Image File Name This is the name of the output image to be generated by ACORN For this tutorial the default location is C Program Files ACORN4 Data Jasper jps6tmrfl Input File Format This parameter specifies whether the input image data are band interleaved by line BIL or band interleave by pixel BIP The Jasper Ridge data set is BIP file format Integer Format This parameter specifies whether the image data are stored as big endian host intel or little endian network or IEEE The Jasper Ridge integer format is big endian Image Dimension These are the dimension of the input image in terms of bands lines samples and offset The offset parameter is the number of bytes used to skip any embedded image headers The dimensions of the Jasper Ridge data set are 224 bands 512 lines and 614 samples with 0 byte offset Imag
2. 04 0 3 1 mm Water Vapor 5 mm Water Vapor 0 2 7 10 mm Water Vapor 1 25 mm Water Vapor 0 50 mm Water Vapor 0 0 T T T 400 0 700 0 1000 0 1300 0 1600 0 1900 0 2200 0 2500 0 Wavelength nm Figure 2 6 Transmittance of the atmosphere with different amounts of water vapor The transmittance effects of the other components of the atmosphere are shown in Figure 2 7 These include molecular absorption due to oxygen carbon dioxide ozone and methane as well as scattering effects of the molecules and aerosol particles in the atmosphere 1 1 1 0 4 Scattering 0 9 0 8 0 7 0 6 0 5 0 4 03 Transmittanc Transmittance 0 2 0 1 0 0 T T T T T 400 0 700 0 1000 0 1300 0 1600 0 1900 0 2200 0 2500 0 Wavelength nm Figure 2 7 Transmittance of the atmosphere due to constituents other than water vapor In addition to the atmospheric transmittance effects on the upwelling radiance measured by a remote sensing instrument some energy is scattered directly from the atmosphere towards the sensor This is generally referred to as atmospheric path radiance or path radiance Figure 2 8 shows an example spectrum of path radiance The aerosol molecular and total path radiance are shown The total path radiance is the radiance that would be measured by a remote sensing instrument if the surface reflectance was zero Radiance W m 2 unysr 60 0 50 0 40 0 30 0 20 0 10 0 17 Aerosol S
3. 1 0x1 M 7 6 0x107 7 4 0x107 E 2 0x10 7 Figure 6 3 Extracted spectra from Cuprite radiance image Table 6 1 Locations of Extracted Spectra Site Sample Line Stonewall Playa 606 293 Opalite Zone w Alunite 554 212 Strongly Argillized Zone w Kaolinite 526 319 Buddingtonite Zone 472 235 Calcite 295 348 These image radiance data contain the effects of the solar illumination two way transmittance and scattering of the atmosphere as well as reflectance of the surface These image extracted spectra are also scaled so that the radiance values fall in a range of efficiently stored integers ACORN mode 3 is designed to use the empirical line method to correct these radiance spectra to reflectance Starting ACORN In this example ACORN Mode 3 will be used to perform an empirical line atmospheric correction on the Cuprite radiance data set 1 Start ACORN by selecting Start Programs ACORNA ACORN The ACORN 4 Control Panel will appear as shown in Figure 6 4 ACORN operates based on control files that provide the parameters and files for the ACORN algorithm 65 ACORN 4 tm Comet Panel F e Eda Run TransterLicense Help ACORN Con tie Aerie a Single Aun Smnory Processing Modo Osips Reterisnce mme File Name Aveileble Duk Space ior Cupit Fla amp Moves Figure 6 4 ACORN Control Panel Reviewing and Editing the Control File Note Except for the examples provided
4. Mode 4 C Program Files ACORN4 Data Jasper jsp4 in x Input Image File Nome Inout File Format Image Dimension EM 8 75 570 nd pz i Output Reflectonce moge File Name Irteger Format ms host intel 614 semples C network IEEE o ofset C Progrem FilestACORNAN Dare Jasperijsp4tm a Mode 4 Specrtic Porameters Image Spectral Calibration File y aviinm fehminm iC Progrem Files ACORN4 Dets Jaspervaerd ved Cancel y Hyperspectral Goin File DIN to radiance W m 27umjs9 C Program Files CORINH DetetJaspersavrd gain wue le Output Spectral Response File frim response c Progr om File sVACOR Nay Des Jospe tm rap le Mullispectal Goin File EL TS radiance to outpuf value C Program Files ACORNS Dete Josper sp4im gain le Figure 7 5 ACORN Mode 4 control file parameter entry window Input Image File Name This is the name of the input radiance image file The default location is C Program FilesNACORNANDataNJasperNjspOrdn Output Reflectance Image File Name This is the name of the output image to be generated by ACORN For this tutorial the default location is C Program Files ACORN4 Data Jasper jps4tm TJ Input File Format This parameter specifies whether the input image data are band interleaved by line BIL or band interleave by pixel BIP The Jasper Ridge data set is BIP file format Integer Format This parameter specifies whether the i
5. 69 Other Tutoria Examples sed we edoe oii ee xU sa pelos decay om ise yes agents ea QE ud AREE EE 70 Chapter 7 Mode 4 Convolution of hyperspectral data to multispectral pale IDESCrIPU OI xo coed ees enero e pe eae SARA othe ore ane Ri aw as ree aa tetas Ree CE Input Image Data ccc vee a ne ro n de easly Ue alias eras eed ergo 7 Statuns ACORN serere ea a Pn E a a tede a EE r seat 75 Reviewing and Editing the Control File sssesssssssssssrureeresrreserrrrrrreeserssseererseesee 76 Running ACORN Mode E neraic o ete baeo tutus E E RE SOA LER 78 ACORN Mode 4 RESUITS od arri uet d s t Do E TOP d a Be HE S RO USE Raw Eo Tera o Yep Ri Che dundee fps 78 Additional Output ull P 79 Otber Tutortal Examples 2 eet e eth eco esse eset ede eM d 80 Chapter 8 Mode 5 Radiative transfer atmospheric correction of calibrated multispectral data Description sses REEL 83 Input Image Dag oci eec end Oden AEEA AA AE OORE gen EE EAEE TORENA DET ode eee 83 Starting ACORN d naa e taxe rate E E tuendi EE LA E op eb E E OEE R td 85 Reviewing and Editing the Control Pile 2 lenceria re ne Free bep Ex eer da VERE E ER UE 85 Running ACORN Mode S aie deee Fis tithes bees ada t ise xiande UE Sex MERI RR RR SEU ERE s 88 ACORN Mode 5 Results iii e trieste eta dee ex redux bus be RR RAD IPEA NUES aa 88 Additional Output Biles oi eoe A I Evae ele teeta 90 Other Tutorial Pram plesiys ccc dee etude RAM e Er eacou ER Ye Rae eros ud ey eR vier er n 90 Chap
6. le Figure 5 4 ACORN Mode 2 control file parameter entry window Input Image File Name This is the name of the input radiance image file The default location is C Program Files ACORN4 Data Cuprite cup1rfl Note You must have created cupirfl by running ACORN Mode 1 on the Cuprite radiance data set Output Reflectance Image File Name This is the name of the output image to be generated by ACORN For this tutorial the default location is C Program Files ACORN4 Data Cuprite cup2rfl Input File Format This parameter specifies whether the input image data are band interleaved by line BIL or band interleave by pixel BIP The Cuprite data set is BIP file format Integer Format This parameter specifies whether the image data are stored as big endian host intel or little endian network or IEEE The Cuprite integer format is big endian Image Dimension These are the dimension of the input image in terms of bands lines samples and offset The Offset parameter is the number of bytes used to skip any embedded image headers The dimensions of the Cuprite data set are 224 bands 512 lines and 614 samples with 0 byte offset Image Target Reflectance Spectrum File This is a single column file with the extracted spectrum from cupIrfl that corresponds to the location where an accurate surface reflectance spectrum has been acquired Table 5 3 shows a portion of this file Negative and noisy values have been set to 0 000 57 T
7. Program Files ACORN4 Data Jasper avr97 gain This is a one column file that is use by ACORN to convert the image file integers to the correct radiance units Table 3 3 shows a subset of this file Table 3 3 Contents of the Jasper Ridge gain file 0 2 0 2 0 2 0 1 0 1 0 1 Offset File This is a file that corrects for any offset in the image file integer values in the conversion to radiance in units of W m 2 um sr For this example the default location is C Program Files ACORN4 Data Jasper avr97 gain This is a one column file that is added to the radiance values Table 3 4 shows a subset of this file Table 3 4 Contents of the Jasper Ridge offest file 30 0 0 0 0 0 0 0 0 0 0 Image Latitude These are the degrees minute seconds of the image data set Each parameter may be integer or decimal If decimal degrees are used the minutes and second field should be zero North latitude is positive The approximate latitude of the Jasper Ridge data set is 37 18 Image Longitude These are the degrees minute seconds of the image data set Each parameter may be integer or decimal If decimal degrees are used the minutes and second field should be zero The approximate longitude of the Jasper Ridge data set is 122 3 East longitude is positive Image Date This is the date of image acquisition in day month year format This example data set was acquired on the 3 of April 1997 Image Time This is the nominal time of a
8. Radiative transfer atmospheric correction of calibrated multispectral data Mode 6 Single spectrum enhancement of a multispectral atmospheric correction Mode 7 Atmospheric correction by the empirical line method for multispectral data This tutorial goes through step by step examples of each of the ACORN modes Because some of the ACORN modes require some of the same input parameters and input files there is considerable overlap in aspects of the descriptions of the different modes When working through this tutorial it may be useful to refer to the ACORN Users Manuel which contains complementary information Note ACORN is not an image processing software package File editing image processing and image viewing capabilities are required to create ACORN support files and to view and assess ACORN results For this tutorial the ENVI software as well as standard text editing and spreadsheet software is used 10 Orgainization This ACORN tutorial includes a brief introductory chapter and then a chapter presenting an overview of some of the factors involved in atmospheric correction The remaining chapters give step by step tutorial examples of each of the ACORN modes Each of the ACORN mode tutorial chapters is designed to stand alone and not require review of other chapters to work through the example This leads to overlap of information and descriptions where ACORN modes require similar files and parameters 11 Chapter 2 Introdu
9. 200 Meters f 18 Deg 1223 Deg Image Acquisition Altitude fo Hin c Min 20 Kilometers fo Sec jo Sec Amospheric Model MLSum C MLWint C Tropic image Dete Image Average Derive Yoter Vapor Time UTC G 940 C 1140 fs Day fi 3 Hours C Both 940 and 1140 Gf Month E Kiinaa Pot rediance in water vopar tit fi 95 Year fe 3 Seconds uc Image Atmosphere visibility Arlilect Suppression ra Kilometers Pyme Kinra P Types ACORN Estimated Visibility Yes Figure 4 4 ACORN Mode 1 5 control file parameter entry window Input Image File Name This is the name of the input radiance image file The default location is C Program Files ACORN4 Data Jasper jsp0rdn Output Reflectance Image File Name This is the name of the output image to be generated by ACORN The default location is C Program Files ACORN4 Data Jasper jspl_5a5rfl Input File Format This parameter specifies whether the input image data are band interleaved by line BIL or band interleave by pixel BIP The Jasper Ridge data set is BIP file format Integer Format This parameter specifies whether the image data are stored as big endian host intel or little endian network or IEEE The Jasper Ridge integer format is big endian Image Dimension These are the dimension of the input image in terms of bands lines samples and offset The offset parameter is the number of bytes used to skip any embedded image headers T
10. AAAA BUDD Figure 3 8 Atmospherically corrected spectra from Jasper Ridge with ACORN Mode 1 and artifact suppression type 1 and 2 Artifact Suppression Type 1 2 and 3 33 Artifact suppression type 3 attempts to address artifacts due to low measured signal For this example from the ACORN Control Panel select Open and open file jspla3 in The default installation location for this file is c Program Files ACORN4 Data Jasper jspla3 in Notice that in the control file editor artifact type 1 2 and 3 are selected Click OK Click Run on the ACORN Control Panel When the run is complete open the output image file with ENVI The location and name for this file specified in the tutorial example control file is c Program Files ACORN4 Data Jasper jspla3rfl With ENVI extract the spectra from the five sites given in Table 3 1 Figure 3 9 shows these extracted spectra In comparison to the spectra shown in Figure 3 6 Figure 3 7 and Figure 3 8 the low signal noisy portions of the spectrum have been suppressed i ENYI Plot Window j loj x File Edit Options Plot Function RAM 4066 Znn SULbD Figure 3 9 Atmospherically corrected spectra from Jasper Ridge with ACORN Mode 1 and artifact suppression type 1 2 and 3 Visibility Estimation ACORN will attempt to estimate the visibility from the data themselves For this example from the ACORN Control Panel select Open and open file jspla3v in The default location for this file
11. Cuprite cup6 in and c Program Files ACORN4 Data Cupriteh cuph6 in You may run these examples and examine the input and output files to gain additional experience with ACORN mode 6 100 101 Chapter 10 Mode 7 Atmospheric correction by the empirical line method for multispectral data The following topics are covered in this chapter DGSCEIDHOTE ved ecoav ec sey eo RATE RU KU Fan ene EEEE E E EEE E E EEEE EEEIEE Dau 102 Input maze Price CL E aaa 102 Starting ACORN T 103 Reviewing and Editing the Control File iie ree ERE RE E RAP I gaps 104 Running ACORN Mode Tessier cusses gud ey eo i uals a vip pave E eoe NER op XEROER Ee SASE 107 ACORN Mode Results eve rh e Sx ext ebbe ete uli eredi epatis 107 Additional Output Files 2 rei tex e e t ee Lax Ye e ese E SA Xu Yea eate veo AE eut 108 Other Tutorial Examples rte er E e EE Rep pU Te HERE ees aes 109 102 Description ACORN uses a dark and bright extracted target spectrum from a multispectral data set and corresponding measured ground spectra for these targets These input pair of band values and pair of known spectra are used to implement an empirical line atmospheric correction ACORN accurately and automatically convolves the known spectra to the spectral characteristics of the multispectral data set for this mode of atmospheric correction This mode is less dependent on the accuracy of the radiometric calibration of the multispectral d
12. Integer Format n2 lines host Intel er 4 samples Output Reflectance Image File Name CAR Files ACORN4 Data J jsp tril Program Files Data Jasper jsp a C network IEEE o offset Mode 1 Specific Parameters ine Specral alban CE Seine O o raian ee c Program Files ACORN Data JespeAawa7 gan A Cancel Mun au eet exProsrem Fies ACORNADatc Jespenioptof m Image Center Image Center Image Mean Elevation 3 Latitude Longitude 200 Meters 7 18 n 22a Image Acquisition Altitude o bin o zo Kilometers o sec f m Atmospheric Model MLSum MLWint C Tropic m Image Date Image Average Derive Water Vapor Time UTC C No C 820 C 940 Lol e P Dey 18 ours ug zu Both 340 and 1140 NN Er i m Fixed Water Vapor d pun BE Panes 10 Millimeters 1997 23 eles Seconde pZ Image Atmosphere Visibility m Artifact Suppression co Kilometers Typel Type2 Type3 ACORN Estimated Visibility Yes Figure 3 4 ACORN Mode 1 control file parameter entry window 29 Input Image File Name This is the name of the input calibrated radiance image file For this example the default location is C Program Files ACORN4 Data Jasper jspO0Ordn Output Reflectance Image File Name This is the name of the output image to be generated by ACORN For this example the default location is C N
13. O 2002 ImSpec LLC All rights reserved ACORN is an ImSpec LLC product with MODTRAN licensed technology ACORN is sold and supported by Analytical Imaging and Geophysics LLC ENVI is a registered trademark of Research Systems Inc ACORN 4 0 Tutorial Stand alone Version Analytical Imaging and Geophysics LLC 4450 Arapahoe Ave Suite 100 Boulder CO 80303 USA Phone 303 926 8284 Fax 303 665 6090 Email acorn 2aigllc com ACORN Version 4 0 January 2002 Edition Copyright ImSpec LLC All Rights Reserved Contents Chapter 1 ACORN Tutorial Overview T tcaducttolo oso cr ee ER D ER eeu he learn TONE ORO RR DOR EN A od RUD RAE E E REY 9 Organizan e Ced pon ay SER n ace tse Si NOU M RUND dva UC ACA NV EM Ne Esa awe EE ite ope 10 Chapter 2 Introduction to Atmospheric Correction Radiance and Reflectance aoi de Ex e rU pad oats ce Rie EE PELA ete coda RE 13 Components of Measured Radiance sssseesssssessseseesee ee e eem mene 14 Atmospheric Correction Options and Methodology eee 17 Multispectral and Hyperspectral Measurements cesses em e 18 Chapter 3 Mode 1 Radiative transfer atmospheric correction of calibrated hyperspectral data PICS CH DUIOM mM c 25 Input Image Data ite e Eee EEEE ACRES EREET EEKE EE RE IER AR UAR S nt 25 Sarni ACORN sets sures da R E 27 Reviewing and Editing the Control File ener rre ever eir Ee rpm xn e XR S 28 Running ACORN Mode fit ue
14. Other Tutorial Examples 55 ae WHO Hed M EN ate iras 90 83 Description ACORN uses radiative transfer calculations to atmospherically correct multispectral data With an input of calibrated multispectral radiance data and baseline atmospheric parameters ACORN produces an output of apparent surface reflectance An accurate spectral response functions file is required for this mode The multispectral data must be spectrally and radiometrically calibrated Figure 8 1 shows four radiance spectra from the example Jasper Ridge multispectral data set and the atmospherically corrected spectra after ACORN mode 5 140 12000 120 Target 1 10000 7 Target 1 o Target 2 Target 2 100 E e Tar E Target 3 S 8000 1 Target 3 4 Target 4 e Target 4 Eom 2 z 8 6000 7 60 uL 3 E ex 2 4000 4 Tm F 407 20 2000 4 E E 0 r r r 7 r O r r r r T 400 700 1000 1300 1600 1900 2200 2500 400 700 1000 1300 1600 1900 2200 2500 Wavelength nm Wavelength nm Figure 8 1 Left radiance spectra for targets in the example Jasper Ridge multispectral data set Right ACORN Mode 5 results showing the apparent reflectance spectra for the same targets Input Image Data For this example of ACORN Mode 5 the AVIRIS data set acquired over Jasper Ridge California convolved to the Landsat Thematic Mapper multispectral bands is used This data set must be generate by following the Mode 4 example in
15. Processing Modo Output Perle rtence miss File Name Aveileble Duk Space tor Output Fla amp Moves Figure 8 4 ACORN Control Panel Reviewing and Editing the Control File Note Except for the examples provided with ACORN you must obtain the appropriate calibration files and data parameters from the data provider 1 Select Open 2 Select the Jasper Ridge mode 5 control file The default location for this file is C Program Files ACORN4 Data Jasper jsp5 in 86 3 Examine the ACORN Mode 5 control file parameter entry panel shown in Figure 8 5 These are the files and parameters necessary to perform a Mode 5 atmospheric correction Each parameter and file is described for the Jasper Ridge example Mode 5 C Program Files ACORN4A Data Jasper jsp5 in E xj Image Dimension fe bands 512 lines Output Reflectance Image File Name Integer Format host Intel e14 samples C Program Files ACORN4 Data Jasper jsp5tmril amp C network IEEE p idt networ offse Input Image File Name Input File Format Boo wayne Program Files ACORN4 Data Jasper isp4tm aj bip bil Mode 5 Specific Parameters Image Spectral Response C Program Files ACORNA Data Jasperiimrsp o File fwvi nm response CAProgram Files ACORN4 Data Jasperitm rsp amp Gain File DN to radiance C Program FilesACORN4 Data JasperjspStm gain Cancel Wim 2 um sr value CAProgram Files ACORN4 Data J
16. This is the altitude of the instrument that acquired the image data The altitude of acquisition of this example Jasper Ridge data set is 20 km Atmospheric Model This option selects the appropriate atmospheric model to be used for atmospheric correction The options are mid latitude summer mid latitude winter and tropical For this example the mid latitude summer atmospheric model is selected Fixed Water Vapor A water vapor amount must be specified in units of precipitable mm of water vapor For this example a value of 15 mm is used Image Atmospheric Visibility This parameter controls the visibility of the atmospheric model used in the atmospheric correction A visibility of 60 km is entered for this example 4 Click OK to complete creation of ACORN mode 5 control file 5 From the ACORN control panel window click Save to save the control file Jsp5 in Running ACORN Mode 5 To execute ACORN mode 5 click Run on the ACORN control panel A processing status box will appear to indicate the progress of the atmospheric correction When the atmospheric correction is complete the program will return to the ACORN Control Panel ACORN Mode 5 Results The primary result of ACORN Mode 5 is the atmospherically corrected image 1 With ENVI open the Jasper Ridge reflectance image The location specified in the tutorial control file is c program files ACORN4 Data Jasper jsp5tmrfl Figure 8 6 shows the reflectance image with bands 3 4 2 d
17. Water Image A second result of the water vapor and liquid water spectral fitting algorithm used in ACORN is a surface liquid water image Figure 4 8 shows the liquid water image for this tutorial example Liquid water is reported in units of expressed path absorption in microns um This parameter may be used to derive vegetation water species type and phonological state properties 1 With ENVI open the Jasper Ridge water image The default location is c program files ACORN4 Data Jasper jspl_5a3rfl wtrl 2 Use the ENVI cursor value location capability to examine the water vapor values From the ENVI image window select Function gt Interactive Analysis gt Cusor Location Value Move the cursor to various parts of the image to see the change in expressed liquid water Liquid water varies from 0 to 4000 um expressed path absorption in um 0 to 4 mm over the image Paved surfaces soils and dry grass give low to zero values Healthy vegetation gives a range of values depending on species water status and phonological state Some of the highest liquid water values are found in the redwood forest in the upper left corner of the data set 50 Figure 4 6 Suface liquid water image from ACORN atmospheric correction mode 1 5 Additional Output Files In addition to the output image file there are several other files created by ACORN in This is the control file that provides the files and parameters that are used by ACORN The file jspl 5a3
18. Window Blank e In the Z profile window click the right mouse button to show the X Y location of the displayed spectrum f To save a spectrum to the blank window drag X Y location label to the new window g Repeat this until you have all the Z profiles in the new window that you wish h These extracted spectra may be saved to an ASCII file by selecting File gt Output Data gt ASCIL EINE loj x File Edit Options Plot Function 4 0x107 2 0107 Figure 10 2 Extracted spectra from Jasper Ridge convolved multipsectral radiance image Table 10 1 Locations of Extracted Spectra Site Sample Line Stanford Golf Course 504 226 Jasper Ridge Grassland 314 159 Plowed Field 402 242 Redwood Forest 102 250 Felt Lake 398 355 These image radiance data contain the effects of the solar illumination two way transmittance and scattering of the atmosphere as well as reflectance of the surface These image extracted spectra are also scaled so that the radiance values fall in a range of efficiently stored integers ACORN mode 7 is designed implement an empirical line atmospheric correction Starting ACORN In this example ACORN Mode 7 will be used to implement an empirical line correction on the Jasper Ridge data set that has been convolved to the Landsat Thematic Mapper multispectral bands 104 1 Start ACORN by selecting Start Programs ACORNA ACORN The ACORN Control Panel will appear as shown in Figure 10 2 ACOR
19. dul ened T EERE 62 Input Image Data eo ec vea eet E E E ETA MR dE RUE IRE eR swe HV DAN Idira edes 62 Starting ACORN T 64 Reviewing and Editing the Control File eese I eme 65 Running ACORN Mode 3 ics eise neuSkyvU e suds le pel es ze deor oo p ennerien e ew Repas viser ere e etaed 68 ACORN Mode 3 Results cci ctetu T Exo ei eux ree nada dta entes ees 68 Additional Output Files 5 2 i te tp t ee eee Pate oe xax e pae etc v EE eae 69 Other Tutorial Examples rte eo rr E ER eI Rr ren EUR A IM ides EREA 70 62 Description ACORN uses a dark and bright extracted target spectrum from a hyperspectral data set and corresponding measured ground spectra for these same targets These four input spectra are used to implement an empirical line atmospheric correction ACORN accurately and automatically convolves the known spectra to the spectral characteristics of the hyperspectral data set for this mode of atmospheric correction This mode is less dependent on the accuracy of the radiometric calibration of the hyperspectral data and can even be run on the raw image data from the image provider To implement ACORN empirical line correction a measured dark and bright target reflectance spectrum is required from within the region of the hyperspectral data set Typically there must be at least 0 10 reflectance between the dark and bright spectra Figure 6 1 shows the measured dark and bright target reflectance s
20. file these will be indicated in this file diagl In the same directory as the output file will be a jsp4tm diagl The diagl file confirms the input parameters used in the atmospheric correction and indicates problems encountered during the run diag2 In the same directory as the output the jsp4tm diag2 file will be created This file contains selected spectral outputs that may be helpful to understand problems with the convolution Other Tutorial Examples Additional tutorial examples are provided with ACORN for the Jasper Ridge AVIRIS and Cuprite Hymap data The default location for these files is c Program Files ACORN4 Data Cuprite cup4 in and c Program Files ACORN4 Data Cupriteh cuph4 in You may run these examples and examine the input and output files to gain additional experience with ACORN mode 4 81 82 Chapter 8 Mode 5 Radiative transfer atmospheric correction of calibrated multispectral data The following topics are covered in this chapter Desortplollo sesir E YOUR eL EU Kp edet aud es yuMes nae de vua osau tcu vv Meu pa CUL TEETE E 83 Input maze Datace ED noe oan bade EE S EEEO wae ed eden 83 Startins ACORN PE 85 Reviewing and Editing the Control File iere re eder ceteris tees 85 Running ACORN MOde 5 un icnetaa deer Eod Ern o wus es og ud ey eR UE SEI EERE e Ra e ADEL SEE 88 ACORN Mode Results uere er St oleo el vali oe e E e esa 88 Additional Output Biles 2 rire ene e n DE RU e tl x e d ee sees ees 90
21. files and parameters that are used by ACORN The file jspl in was created in the default location for this tutorial example eco In the same file location of the jsp1 in file will be a jspl in eco This file is an echo of the input file as it is being interpreted by the ACORN software If problems are detected interpreting the control file these will be indicated in this file diagl In the same directory as the output reflectance file will be a jsplrfl diagl The diag file confirms the input parameters used in the atmospheric correction and indicates problems encountered during the run diag2 In the same directory as the output reflectance the jspIrfl diag2 file will be created This file contains selected spectral outputs that may be helpful to understand problems with the atmospheric correction Artifact Suppression Type 1 Artifact suppression type 1 attempts to address spectral calibration mismatches between the image data set and the radiative transfer code model of the atmosphere For this example from the ACORN Control Panel select Open and open file jsplal in The default installation location for this file is c Program Files ACORN4 Data Jasper jsplal in Notice that in the control file editor artifact type 1 is selected Click OK Click Run on the ACORN Control Panel When the run is complete open the output image file with ENVI The default location and name for this file is c Program Files ACORN4 Data Jasper jsplalrfl W
22. in was created in the default location for this tutorial example eco In the same file location of the jspl 5a3 in file will be a jsp1_5a3 in eco This file is an echo of the input file as it is being interpreted by the ACORN software If problems are detected interpreting the control file these will be indicated in this file diagl In the same directory as the output reflectance file will be a jspl 5a3rfl diagl The diagl file confirms the input parameters used in the atmospheric correction and indicates problems encountered during the run diag2 In the same directory as the output reflectance the jsp1_Sa3rfl diag2 file will be created This file contains selected spectral outputs that may be helpful to understand problems with the atmospheric correction Other Tutorial Examples Additional tutorial examples are provided with ACORN for the Cuprite Nevada AVIRIS and Hymap data The default location for these files is c Program FilesNACORNAMDataNCupriteNcupl 5 in and c Program Files ACORN4 Data Cupriteh cuph1_5 in You may run these examples and examine the input and output files to gain additional experience with ACORN mode 1 5 Chapter 5 Mode 2 Single spectrum enhancement of a hyperspectral atmospheric correction The following topics are covered in this chapter 51 Description a oc los c Lee n S ert d iae se s NS LIU eee i ies ota ido Input Image Data MM Staron ACORN eI E Reviewing and Editing the Control Pile veces
23. in the tutorial is c Program Files ACORN4 Data Jasper jspla3v in Notice that in the control file editor artifact type 1 2 3 and estimate visibility are selected 36 Click OK Click Run on the ACORN Control Panel When the run is complete open the output image file with ENVI The location and name for this file in the tutorial is c Program Files ACORN4 Data Jasper jspla3vrfl With ENVI extract the spectra from the five sites given in Table 3 1 For comparison spectra are shown in Figure 3 10 where ACORN was run with a fixed visibility of 20 km 20 km is too hazy an atmosphere for this data set and results in negative reflectance values in the visible portion of the spectrum The ACORN estimated visibility spectra in Figure 3 11 give a better result ENVI Plot Window J n x File Edit Options Plot Function 1000 BAAN BUbDDb 6000 4000 Figure 3 10 Atmospheric correction with fixed 20 km visibility used 20 km is excessively haze and causes negative reflectance results in the visible portion of the spectrum 37 Ini xj File Edit Options Plot Function 10000 8000 6000 4000 DNAN 2000 1000 Wayelen qt h Figure 3 11 Atmospheric correction with ACORN visibility estimation used Other Tutorial Examples Additional tutorial examples are provided with ACORN for the Cuprite Nevada AVIRIS and Hymap data The default location for these files is c Program Files ACORN4 Data Cuprite cupl in an
24. is spectral wavelength The solution of this equation for apparent surface reflectance is given in Equation 2 2 PA I FO A Td A Tu a m Lt A FO A pa A m 8 A Equation 2 2 These and other mathematical equations are used in ACORN for each of the radiative transfer based atmospheric correction modes Multispectral and Hyperspectral Measurements The two principal types of remote sensing data are multispectral and hyperspectral Multispectral instruments and measurement were developed first Hyperspectral instruments were conceived and developed only in the 1980s Figure 2 10 shows the spectral response functions for the Landsat multispectral sensor Landsat has 6 multispectral bands in the solar reflected portion of the electromagnetic spectrum These response functions describe how the upwelling radiance arriving at Landsat is partitioned into each mulispectral band Figure 2 11 shows an image of the Jasper Ridge California in the southern San Francisco Bay area Figure 2 12 shows an example of upwelling radiance measured through the Landsat spectral response functions for several surface targets Figure 2 13 shows the corresponding reflectance for these targets after ACORN atmospheric reflectance j L Response Normalized Response Ooocococococ Bo O0 ucc o L L L 1 fi fi ooo Re N UC L I 1 400 700 1000 1300 1600 1900 2200 2500 Wavelength nm Figure 2 10 Spectral response functio
25. jspOrdn 3 Select bands 30 40 20 to display as red green blue This is done with in the Available Bands List window by clicking the RGB Color option and then scrolling and clicking on band 30 40 and 20 in that order Then click the Load Band button This image is shown in Figure 7 2 Figure 7 3 shows a set of extracted spectra from the Jasper Ridge data Table 7 1 gives the site and location of these extracted spectra 74 D 1 A Sand J0 G Band 40 B Hand 20 jsplrda Figure 7 2 Jasper Ridge radiance image 4 Extract and examine the radiance spectra with ENVI Z profiles a This is done in the ENVI image window by selecting Functions gt Profiles gt Z Profiles b To move the cursor to a specific location from the ENVI image window select Functions gt Interactive Analysis gt Pixel Locator c In the pixel locator window enter the X and Y location and click Apply d To extract and save spectra select Option New Window Blank e In the Z profile window click the right mouse button to show the X Y location of the displayed spectrum f To save a spectrum to the blank window drag X Y location label to the new window g Repeat this until you have all the Z profiles in the new window that you wish h These extracted spectra may be saved to an ASCII file by selecting File gt Output Data ASCII 75 ENVI Plot Window loj x File Edit Options Plot Function 4000 Figure 7 3 Extracted spectra from
26. mode 2 click Run on the ACORN control panel A processing status box will appear to indicate the progress of the atmospheric correction When the atmospheric correction is complete the program will return to the ACORN Control Panel 58 ACORN Mode 2 Results The principal result of ACORN Mode 2 is the single spectrum enhanced reflectance image 1 With ENVI open the Cuprite single spectrum enhanced image The default location for the tutorial is c program files ACORN4 Data Cuprite cup2rfl Figure 5 5 shows the reflectance image with bands 200 130 30 displayed as Red Green Blue respectively 2 Extract the single spectrum enhanced spectra from the sites in table 5 1 The extracted spectra are shown in Figure 5 6 3 Compare the extracted single spectrum enhanced spectra with the input reflectance spectra in Table 5 1 The spectral roughness has been removed Spectral artifacts remain only in the 1400 and 1900 nm region where the signal is extremely low due to the absorption of atmospheric water vapor 1 Send 200 G Band 130 8 Band ES Figure 5 5 Single Spectrum Enhance image following use of ACORN Mode 2 59 Ini xj File Edit Options Plot Function 100 B8000 4000 200 2000 c IU Lb Figure 5 6 Extracted spectra from Cuprite data set after Mode 2 Single Spectrum Enhancement Additional Output Files In addition to the output image file there are several other files created by ACORN in This is
27. the control file that provides the files and parameters that are used by ACORN The file cup2 in was created in the default location for this tutorial example eco In the same file location of the cup2 in file will be a cup2 in eco This file is an echo of the input file as it is being interpreted by the ACORN software If problems are detected interpreting the control file these will be indicated in this file diagl In the same directory as the output reflectance file will be a cup2rfl diagl The diagl file confirms the input parameters used in the atmospheric correction and indicates problems encountered during the run diag2 In the same directory as the output reflectance the cup2rfl diag2 file will be created This file contains selected spectral outputs that may be helpful to understand problems with the atmospheric correction Other Tutorial Examples Additional tutorial examples are provided with ACORN for the Jasper Ridge AVIRIS and Cuprite Hymap data The default location for these files is c Program Files ACORN4 Data Jasper jsp2 in and c Program Files ACORN4 Data Cupriteh cuph2 in You may run these examples and examine the input and output files to gain additional experience with ACORN mode 2 60 Chapter 6 Mode 3 Atmospheric correction using the empirical line method for hyperspectral data The following topics are covered in this chapter Descriptio sesioni ire xao Reo CAU KU Code ne aw SYM eden Masa Eod ves uve Ea on
28. you wish h These extracted spectra may be saved to an ASCII file by selecting File gt Output Data ASCII 42 ID x Edit Options Plot Function File 4000 D 4 Figure 4 2 Extracted spectra from Jasper Ridge radiance image Table 4 1 Locations of Extracted Spectra Site Sample Line Stanford Golf Course 504 226 Jasper Ridge Grassland 314 159 Plowed Field 402 242 Redwood Forest 102 250 Felt Lake 398 355 These image radiance data contain the effects of the solar illumination two way transmittance and scattering of the atmosphere as well as reflectance of the surface These image extracted spectra are also scaled so that the radiance values fall in a range of efficiently stored integers ACORN mode 1 5 is designed to use input and derived parameters with spectral fitting for water vapor and surface liquid water to assess and correct for these atmospheric effects Starting ACORN In this example ACORN Mode 1 5 will be used to atmospherically correct the Jasper Ridge calibrated radiance data set 1 Start ACORN by selecting Start gt Programs gt ACORN4 gt ACORN The ACORN Control Panel will appear as shown in Figure 4 3 ACORN operates based on control files that provide the parameters and files for implementation of the atmospheric correction 43 ADORN 4 im Dormi Panel F e Eda Hun TransterLicense Help ACORN Candi rie ajajaja a Single Aun Sumner Processing Modo O
29. 00 130 30 to display as red green blue This is done with in the Available Bands List window by clicking the RGB Color option and then scrolling and clicking on band 200 130 and 30 in that order Then click the Load Band button The resulting displayed image is shown in Figure 6 2 Figure 6 3 shows a set of extracted radiance spectra the Cuprite Table 6 1 gives the site and location of these extracted spectra Extract these spectra for later comparison with empirical line result 63 ey ti R Band 200 G Hand 13 8 Band EIE Figure 6 2 Cuprite AVIRIS radiance image 4 Extract and examine the radiance spectra with ENVI Z profiles a This is done in the ENVI image window by selecting Functions gt Profiles gt Z Profiles b To move the cursor to a specific location from the ENVI image window select Functions gt Interactive Analysis gt Pixel Locator c In the pixel locator window enter the X and Y location and click Apply d To extract and save spectra select Option gt New Window Blank e In the Z profile window click the right mouse button to show the X Y location of the displayed spectrum f To save a spectrum to the blank window drag X Y location label to the new window g Repeat this until you have all the Z profiles in the new window that you wish h These extracted spectra may be saved to an ASCII file by selecting File gt Output Data ASCII 64 ID x Edit Options Plot Function File 1 2x1 o
30. 8 improve atmospheric correction results The conversion of hyperspectral data to multispectral data for investigation of multispectral solutions to remote sensing problems is also part of the core capabilities of ACORN The most advanced form of atmospheric correction offered in ACORN is radiative transfer based Radiative transfer atmospheric correction of calibrated data uses both the calibrated data and provided parameters to derive and model the absorption and scattering characteristics of the atmosphere These atmospheric characteristics are then used to invert the radiance to apparent surface reflectance The approach for atmospheric correction is based in the following equations that can be found or derived from the information in the text Radiative Transfer by Chandrasekhar December 1960 Dover ISBN 0486605906 In simplified terms Equation 2 1 gives the relationship between contributions between the solar source atmosphere and surface to the radiance measured by an earth looking sensor for a homogeneous plane parallel atmosphere LECA FO A pa A TANPON TUAN sP V Equation 2 1 In this equation Lt is the total radiance arriving at the sensor FO is the top of the atmospheric solar irradiance pa is the reflectance of the atmosphere Td is the downward transmittance of the atmosphere p is the spectral reflectance of the surface Tu is the upward transmittance of the atmosphere s is the downward reflectance of the atmosphere A
31. Data Jasper jsp7tmd ext amp Dark Target Reflectance Spectrum File wvl nm rff CAProgram Filesy amp CORN4AJDatayJaspenjsp tmd meas amp Bright Target Image Values 7 z z File value CAProgram Files ACORN4 Data Jasperjsp tmb ext amp Bright Target Reflectance n Spectrum cs wel tnm rfl CAProgram Files ACORN4 Datal Jasper jsp7tmb meas al Figure 10 3 ACORN Mode 7 control file parameter entry window Input Image File Name This is the name of the input radiance image file The default location is C Program Files ACORN4 Data jasper jsp4tm Output Reflectance Image File Name This is the name of the output image to be generated by ACORN For this tutorial the default location is C Program Files ACORN4 Data Jasper jps7tmrfl Input File Format This parameter specifies whether the input image data are band interleaved by line BIL or band interleave by pixel BIP The Jasper Ridge data set is BIP file format Integer Format This parameter specifies whether the image data are stored as big endian host intel or little endian network or IEEE The Jasper Ridge integer format is big endian Image Dimension These are the dimension of the input image in terms of bands lines samples and offset The offset parameter is the number of bytes used to skip any embedded image headers The dimensions of the Jasper Ridge data set are 6 bands 512 lines and 614 samples with 0 byte offset Image Spectral Response File Th
32. Jasper Ridge radiance image Table 7 1 Locations of Extracted Spectra Site Sample Line Stanford Golf Course 504 226 Jasper Ridge Grassland 314 159 Plowed Field 402 242 Redwood Forest 102 250 Felt Lake 398 355 Starting ACORN In this example ACORN Mode 4 will be used to perform spectral convolution on the Jasper radiance data set 1 Start ACORN by selecting Start Programs ACORNA ACORN The ACORN Control Panel will appear as shown in Figure 7 4 ACORN operates based on control files that provide the parameters and files for the ACORN algorithm Lx F e Ede Hun TransferLicense Help a a a ACORN Commi ie a Z a Singe Aun Sumner Proccts rg Modo i tof Available Duk Space tor Ou ut Fie Mover 76 Figure 7 4 ACORN Control Panel Reviewing and Editing the Control File Note Except for the examples provided with ACORN you must obtain the appropriate calibration files and data parameters from the data provider 1 From the ACORN Control Panel select Open 2 For this example choose the Jasper Ridge Mode 4 tutorial control file The default installation location for this control file is C Program Files ACORN4 Data Jasper jsp4 in 3 Examine the ACORN control file parameter entry panel shown in Figure 7 5 These are the files and parameters necessary to perform the hyperspectral to multispectral convolution Each parameter and file is described below for this tutorial example
33. N operates based on control files that provide the parameters and files for the ACORN algorithm ACORN 4 tm Commi Panel F e Eda Run TransterLicense Help ACORN Con Me ajajaja a Singe Aun Sumner Procceainy Modo Output Retectsnce mee File Name Ajeilabls Duk Space ior Cupit Fla amp a Moves Figure 10 2 ACORN Control Panel Reviewing and Editing the Control File 1 From the ACORN Control Panel select Open 2 For this example choose the Japser Ridge Mode 7 example control file The default installation location for this control file is C Program Files ACORN4 Data Jasper jsp7 in 3 Examine the ACORN control file parameter entry panel shown in Figure 10 3 These are the files and parameters necessary to perform the atmospheric correction Each parameter and file is described below for this tutorial example 105 Mode 7 C Program Files ACORN4 Data Jasper jsp7 in E x Input Image File Name r Input File Format Image Dimension bip bil 6 bands C Program Files ACORN4 Data Jasper jsp4tm a Integer Format 512 lines Output Reflectance Image File Name host Intel e14 samples C Program Files ACORN4 Data Jasper jsp7tmrf C network IEEE dodi netwarl offse Mode Specific Parameters Image Spectral Response File CAProgram Files ACORN4 Data Jaspertm rsp amp wvl nm response Cancel Dare vege me Nene C Program Files ACORN4
34. Program Files ACORN4 Data Jasper jsplirfl Input File Format This parameter specifies whether the input image data are band interleaved by line BIL or band interleave by pixel BIP The Jasper Ridge data set is BIP file format Integer Format This parameter specifies whether the image data are stored as big endian host intel or little endian network or IEEE The Jasper Ridge integer format is big endian Image Dimension These are the dimension of the input image in terms of bands lines samples and offset The offset parameter is the number of bytes used to skip any embedded image headers The dimensions of the Jasper Ridge data set are 224 bands 512 lines and 614 samples with 0 byte offset Image Spectral Calibration file This is the spectral calibration file for the input image The format is ASCII The default location is C Program Files ACORN4 Data Jasper avr97 wvl This is a two column file The first colum is the center position of each spectral band in nanometers The second column is the full width at half maximum FWHM of the appropriate Gaussian function for that spectral band in nanometers Table 3 2 shows a subset of this file Table 3 2 Jasper Ridge spectral calibration file 369 85 9 61 379 69 9 58 389 53 9 55 2486 99 10 07 2496 90 10 05 2506 81 10 03 Gain File This is the file that converts the image file integer values to radiance in units of W m 2 um sr The default location for this example is C
35. RN Tutorial Overview The following topics are covered in this chapter Introduction This tutorial is designed to introduce you to basic concept of atmospheric correction and the full capabilities of the Atmospheric COrrection Now ACORN software Data sets acquired by the Airborne Visible Infrared Imaging Spectrometer AVIRIS from Cuprite Nevada and Jasper Ridge California are used to explore the full range of options in ACORN These example data sets are provided with the ACORN software as well as an example data set acquired by the HYMAP sensor over Cuprite Nevada All the files necessary to run these tutorial examples are provided with the ACORN software The tutorial uses the ENVI software for display and extraction of spectra If other image processing software is used similar display and data extraction capabilities will be required The Atmospheric CORection Now ACORN software has been developed to offer a range of atmospheric correction capabilities These capabilities include Mode 1 Radiative transfer atmospheric correction of calibrated hyperspectral data Mode 1 5 Radiative transfer atmospheric correction of calibrated hyperspectral data with water vapor and liquid water spectral fitting Mode 2 Single spectrum enhancement of a hyperspectral atmospheric correction Mode 3 Atmospheric correction using the empirical line method for hyperspectral data Mode 4 Convolution of hyperspectral data to multispectral data Mode 5
36. able 5 3 Cuprite Image Target Reflectance Spectrum File 0 000 0 000 516 721 1399 558 1863 000 3529 698 5338 349 5243 674 Image Spectral Calibration file This is the spectral calibration file for the input image The default location is C Program Files ACORN4 Data Cuprite avr97 wvl This is a two column file The first column is the center position of each spectral band in the image in nanometers The second column is the full width at half maximum FWHM of the appropriate Gaussian function to describe the spectral response function of the band in nanometers Table 5 2 shows a subset of this file Table 5 3 Cuprite image spectral calibration file 369 85 9 61 379 69 9 58 389 53 9 55 2486 99 10 07 2496 90 10 05 2506 81 10 03 Measured Target Reflectance Spectrum File This is the measured reflectance for the same target as the Image Target Reflectance Spectrum File The default location of the file for this tutorial is C Program Files ACORN4 Data Cuprite Cup2 meas This is atwo column file The first column is wavelength in nm and the second column is reflectance The reflectance is multiplied by 10000 to have the same scaling as the Image Target Reflectance Spectrum File Table 5 4 shows a portion of this file Table 5 4 Contents of the Measured Target Reflectance Spectrum File 350 1636 862 351 1638 537 352 1642 535 2503 4079 836 2504 4081 076 2505 4082 106 Running ACORN Mode 2 To execute ACORN
37. al response function of the band in nanometers Table 6 2 shows a subset of this file 67 Table 6 2 Cuprite image spectral calibration file 369 85 9 61 379 69 9 58 389 53 9 55 2486 99 10 07 2496 90 10 05 2506 81 10 03 Dark Target Image Spectrum File This is a single column file with the extracted dark target spectrum from the input image This spectrum corresponds to the location where an accurate surface reflectance spectrum has been acquired The default location of the file for this tutorial is C Program Files ACORN4 Data Cuprite Cup3d ext Table 6 3 shows a portion of this file Table 6 3 Dark Target Image Spectrum File 864 64 1147 03 1587 77 10 35 15 77 11 48 Dark Target Reflectance File This is the measured reflectance for the dark target The default location of the file for this tutorial is C Program Files ACORN4 Data Cuprite Cup3d meas This is a two column file The first column is wavelength in nm and the second column is reflectance The reflectance is multiplied by 10000 to product a scaling between 0 and 10000 in the output file Table 6 4 shows a portion of this file Table 6 4 Dark Target Reflectance File 350 1636 86 351 1638 53 352 1642 53 2503 4079 83 2504 4081 07 2505 4082 10 Bright Target Image Spectrum File This is a single column file with the extracted dark target spectrum from the input image This spectrum corresponds to the location where an accurate surface reflect
38. ance spectrum has been acquired The default location of the file for this tutorial is C Program Files ACORN4 Data Cuprite Cup3b ext Table 6 5 shows a portion of this file 68 Table 6 5 Bright Target Image Spectrum File 1524 44 2022 41 2694 53 31 85 45 26 31 55 Bright Target Reflectance File This is the measured reflectance for the bright target The default location of the file for this tutorial is C Program Files ACORN4 Data Cuprite Cup3b meas This is a two column file The first column is wavelength in nm and the second column is reflectance The reflectance is multiplied by 10000 to product a scaling between O0 and 10000 in the output file Table 6 6 shows a portion of this file Table 6 6 Bright Target Reflectance File 351 462 23 351 469 62 352 473 59 2503 1174 56 2504 1173 76 2505 11732 Running ACORN Mode 3 To execute ACORN mode 3 click Run on the ACORN control panel A processing status box will appear to indicate the progress of the atmospheric correction When the empirical atmospheric correction is complete the program will return to the ACORN Control Panel ACORN Mode 3 Results The principal result of ACORN Mode 3 is the empirical line reflectance image 1 With ENVI open the Cuprite empirical line reflectance image The default location for the tutorial is c program files ACORN4 Data Cuprite cup3rfl Figure 6 6 shows the reflectance image with bands 200 130 30 displayed as Red Green B
39. ansfer code model of the atmosphere iii Artifact suppression type 3 attempts to address artifacts due to low measured signal For this example all artifact suppression options are selected Image Elevation This is the average elevation of the surface in the input image in meters The approximate average elevation of the Jasper Ridge example data set is 200 m Image Acquisition Altitude This is the altitude of the instrument that acquired the image data in kilometers The altitude of acquisition of this example Jasper Ridge data set is 20 km Atmospheric Model This option selects the appropriate atmospheric model to be used for atmospheric correction The options are mid latitude summer mid latitude winter and tropical For this example the mid latitude summer atmospheric model is selected Derive Water Vapor This option selects the type of water vapor derivation for ACORN Mode 1 5 1 940 water vapor band ii 1140 water vapor band iii 940 and 1140 water vapor band For this example the option to use both the 940 and 1140 nm water vapor bands is selected Path Radiance This option includes fine tuning of the path radiance parameter in the spectral fitting of water vapor and liquid water This may improve the quality of the water vapor and liquid water result For this example this option is selected Image Atmospheric Visibility This parameter controls the visibility of the atmospheric model used in the atmospheric correction A vi
40. area E 1 A Bond 1 G Band 4 B Band 2 jopbitreedl Figure 9 5 Multispectral Single Spectrum Enhanced image following use of ACORN Mode 6 99 In x Edit Options Plot Function File 4000 3000 1000 Figure 9 6 Extracted spectra from Jasper Ridge data set after Mode 6 Single Spectrum Enhancement Additional Output Files In addition to the output image file there are several other files created by ACORN jin This is the control file that provides the files and parameters that are used by ACORN The file jsp6 in was created in the default location for this tutorial example eco In the same file location of the jsp6 in file will be a jsp6 in eco This file is an echo of the input file as it is being interpreted by the ACORN software If problems are detected interpreting the control file these will be indicated in this file diagl In the same directory as the output file will be a jsp6tmrfl diagl The diagl file confirms the input parameters used in the atmospheric correction and indicates problems encountered during the run diag2 In the same directory as the output the jsp6tmrfl diag2 file will be created This file contains selected spectral outputs that may be helpful to understand problems with the convolution Other Tutorial Examples Additional tutorial examples are provided with ACORN for the Cuprite AVIRIS and Cuprite Hymap data The default location for these files is c Program Files ACORN4 Data
41. asperjspStm gain amp Offset File Wim PST CAProgram Files ACORN4 Data Jasperisp5tm off amp Image Center r Image Center Image Mean Elevation 3 Latitude Longitude zoo Meters B ih Image Acquisition Altitude in 20 Kilometers LoS Atmospheric Model Image Average MLSum C ML Wint C Tropic mete Fixed Water Vapor E Day fi 3 Hours ns Millimeters L 4 57 i E Month Mines Image Atmosphere Visibility 1 997 Year 23 Seconds 60 Kilometers Figure 8 5 ACORN 4 Mode 5 control file parameter entry window Input Image File Name This is the name of the input radiance image file For this example the default location isC Program Files ACORN4 Data Jasper jsp4tm Output Reflectance Image File Name This is the name of the output image to be generated by ACORN Mode 5 For this example the default location is C Program Files ACORN4 Data Jasper jsp5tmrfl Input File Format This parameter specifies whether the input image data are band interleaved by line BIL or band interleave by pixel BIP The Jasper Ridge data set is BIP file format Integer Format This parameter specifies whether the image data are stored as big endian host intel or little endian network or IEEE The Jasper Ridge integer format is big endian Image Dimension These are the dimension of the input image in terms of ba
42. ata In some cases raw integer values can be used Input Image Data For this example the AVIRIS data set acquired over Jasper Ridge that has been convolved to Landsat thematic mapper bands is used This convolution is achieved by using ACORN mode 4 as described in an earlier chapter of this tutorial Begin by examining the Jasper Ridge convolved multispectral data 1 Start ENVI software on your computer 2 Open the Jasper Ridge data The default location is c program files ACORN4 Data Jasper jsp4tm 3 Select bands 3 4 2 to display as red green blue This is done with in the Available Bands List window by clicking the RGB Color option and then scrolling and clicking on band 3 4 and 2 in that order Then click the Load Band button This image is shown in Figure 10 1 Figure 10 2 shows a set of extracted spectra from the Jasper Ridge data Table 10 1 gives the site and location of these extracted spectra O 1 R Based 3 G Band 4 8 Band 2 jsp4tn i Figure 10 1 Jasper Ridge Multispectral convolved radiance image 4 Extract and examine the radiance spectra with ENVI Z profiles a This is done in the ENVI image window by selecting Functions gt Profiles gt Z Profiles 103 b To move the cursor to a specific location from the ENVI image window select Functions gt Interactive Analysis gt Pixel Locator c In the pixel locator window enter the X and Y location and click Apply d To extract and save spectra select Option New
43. cattered Molecular Scattered 0 0 400 0 Path Radiance T T T T 700 0 1000 0 1300 0 1600 0 1900 0 2200 0 2500 0 Wavelength nm Figure 2 8 Spectrum of the atmospheric path radiance scattered in the direction of a remote sensing instrument The total radiance measured by a remote sensing instrument includes both the path radiance and the surface reflected radiance The surface reflected radiance is the solar energy that has been reflected by the surface in the direction of the sensor The reflected radiance plus the path radiance is the total radiance measured by the remote sensing instrument Figure 2 9 shows the total radiance path radiance and reflected radiance for a 0 25 reflectance surface Radiance W m 2 um sr 140 0 120 0 4 100 0 4 80 0 4 60 0 40 0 5 20 0 0 0 Path Radiance Surface Reflected Total T dien ee ee 400 0 700 0 1000 0 1300 0 1600 0 1900 0 2200 0 2500 0 Wavelength nm Figure 2 9 The total reflected and path radiance for a 0 25 reflectance surface Atmospheric Correction Options and Methodology ACORN offers a range of strategies for atmospheric correction These include both empirical and radiative transfer code based methods for atmospheric correction of both hyperspectral and multispectral data sets ACORN also offers several artifact suppression options as well as single spectrum enhancement options to 1
44. cquisition in hours minutes and seconds The time must be Greenwich Mean Time GMT Each parameter may be integer or decimal The example Jasper Ridge data set was acquired at 19 57 23 GMT Artifact Suppression This option allows selection of artifact suppression options 1 Artifact suppression type 1 attempts to address spectral calibration mismatches between the image data set and the radiative transfer code model of the atmosphere ii Artifact suppression type 2 attempts to address radiometric calibration mismatches between the image data set and the radiative transfer code model of the atmosphere iii Artifact suppression type 3 attempts to address artifacts due to low measured signal For this example no artifact suppression options are selected Image Elevation This is the average elevation of the surface in the input image The nominal elevation of the Jasper Ridge example data set is 200 m Image Acquisition Altitude This is the altitude of the instrument that acquired the image data in kilometers The altitude of acquisition of this example Jasper Ridge data set is 20 km Atmospheric Model This option selects the appropriate atmospheric model to be used for atmospheric correction The options are mid latitude summer mid latitude winter and tropical For this example the mid latitude summer atmospheric model is selected Derive Water Vapor This option selects the type of water vapor derivation for ACORN Mode 1 ACORN derive
45. ction to Atmospheric Correction The following topics are covered in this chapter Radiance and Bell ctdneedo ss os co E NI va op bbe eal teh RRL aa keeles sibl Ritalin acted 13 Components of Measured Radiance iiie epi tret e ERE VERE E E KERNSR AER epeRS agus 14 Atmospheric Correction Options and Methodology eee 17 Multispectral and Hyperspectral Measurements cesses em e 18 13 Radiance and Reflectance All airborne and spaceborne remote sensing instrument measure the upwelling radiance that arrives at the sensor The upwelling radiance results from the exo atmospheric solar irradiance the two way transmittance and scattering of the atmosphere and the reflectance of the surface Figure 2 1 shows a radiance image of the Cuprite Nevada data set Figure 2 2 shows the measured radiance spectrum extracted from Stonewall Playa at the right central edge of the image a 1 R Band 200 G Band 120 6 Band STORIE Figure 2 1 Image of Cuprite Nevada acquired by the AVIRIS hyperspectral sensor Wavelengths 655 8 1483 3 and 2268 4 nm are displayed as blue green and red respectively 300 250 4 200 4 Stonewall Playa 150 4 100 Radiance W m 2 um sr 50 4 400 700 1000 1300 1600 1900 2200 2500 Wavelength nm 14 Figure 2 2 Spectrum extracted from Stonewall playa located on the right central edge of the Cuprite Nevada radiance image This radiance spectrum is domi
46. cup 3b meas Figure 6 5 ACORN Mode 3 control file parameter entry window Input Image File Name This is the name of the input radiance image file The default location is C Program FilesNACORNANDataNCupriteNcupOrdn Output Reflectance Image File Name This is the name of the output image to be generated by ACORN For this tutorial the default location is C Program Files ACORN4 Data Cuprite cup3rfl Input File Format This parameter specifies whether the input image data are band interleaved by line BIL or band interleave by pixel BIP The Cuprite data set is BIP file format Integer Format This parameter specifies whether the image data are stored as big endian host intel or little endian network or IEEE The Cuprite integer format is big endian Image Dimension These are the dimension of the input image in terms of bands lines samples and offset The offset parameter is the number of bytes used to skip any embedded image headers The dimensions of the Cuprite data set are 224 bands 512 lines and 614 samples with 0 byte offset Image Spectral Calibration file This is the spectral calibration file for the input image The default location is C Program Files ACORN4 Data Cuprite avr97 wvl This is a two column file The first column is the center position of each spectral band in the image in nanometers The second column is the full width at half maximum FWHM of the appropriate Gaussian function to describe the spectr
47. d c Program Files ACORN4 Data Cupriteh cuphl in You may run these examples and examine the input and output files to gain additional experience with ACORN mode 1 38 Chapter 4 Mode 1 5 Radiative transfer atmospheric correction of calibrated hyperspectral data with water vapor and liquid water spectral fitting The following topics are covered in this chapter Descriptions cocti deter eao En E EAE s cevegnsde tdi avi EAE I uu PeA IU UR aste oL SEES 40 Input Image Data iile TP EE AR ua IE ERR ER E Uo SUEDE RE heeds RIDES IDA 40 Starine ACORN S 2532255 55250 ease n aue M Sedan eR nba cC t OI 42 Reviewing and Editing the Control BIH amp 2 eoe ebore nese vende a Sueno DE Oe a eer deed E eer 43 Running ACORN Mode 1 5 dee ieosstesesosr Sas ee Red ades t deese dosi duo te EE D MR des ouis 46 Reflectance Results o ePi dr Fai Mu e DI eee lation EUN Ub DR EE 47 Water Vapor mage e MM 48 Lig id W ALGER bim uS 49 Additonal Output Files seins ado ate een eek e tr Eden EE ebd ERREUR EM A NE PEERS 50 Other Tutorial Examples iei iii ren ee dato x eae eei bak ua cas EU EE aoe ei eae meee 50 40 Description ACORN mode 1 5 is a new mode introduced in ACORN version 4 1 that uses radiative transfer calculations and the measured calibrated hyperspectral data to deduce a subset of the atmospheric effects present in the hyperspectral data set This mode includes spectral fitting to simultaneously determine the water va
48. e ACORN mode 7 click Run on the ACORN control panel A processing status box will appear to indicate the progress of the atmospheric correction When the atmospheric correction is complete the program will return to the ACORN Control Panel ACORN Mode 7 Results The principal result of ACORN Mode 7 is the empirical line reflectance image 1 With ENVI open the Jasper Ridge empirical line reflectance image The default location for the tutorial is c program files ACORN4 Data Jasper jsp7tmrf1 Figure 10 4 shows the reflectance image with bands 3 4 2 displayed as Red Green Blue respectively 2 Extract the single spectrum enhanced spectra from the sites in table 10 1 The extracted spectra are shown in Figure 10 5 108 3 Compare the extracted single spectrum enhanced spectra with the input radiance spectra in Figure 10 2 The effects of the illumination and the atmosphere have been suppressed Figure 10 4 Multispectral empirical line image following use of ACORN Mode 7 amp ENVI Plot Window E n x File Edit Options Plot Function 4000 Figure 10 5 Extracted spectra from Jasper Ridge data set after Mode 7 empirical line Additional Output Files In addition to the output image file there are several other files created by ACORN in This is the control file that provides the files and parameters that are used by ACORN The file jsp7 in was created in the default location for this tutorial example 109 ec
49. e Spectral Response File This is a two column ASCII file containing the multispectral spectral response functions The first column is the wavelength in nanometers and the second column is the response value for the multispectral band The spectral responses for each band are contained in this one file with the end of each band indicated by a negative value in the second column The default location of the file for this tutorial is C Program Files ACORN4 Data Jasper tm rsp Table 9 2 shows a portion of the spectral response file 97 Table 9 2 Mulispectral Spectral Response File 428 0 0000 430 0 0021 432 0 0087 434 0 0154 436 0 0221 500 0 9791 502 0 9883 504 1 0000 506 0 9609 508 0 914 552 0 0003 554 0 0001 556 0 0001 502 0 0000 504 0 0006 506 0 0057 Image Target Spectrum File This is a single column file with the extracted spectrum from jsp5tmrfl that corresponds to the location where a accurate surface reflectance spectrum has been acquired The default location of the file for this tutorial is C Program Files ACORN4 Data Jasperr jsp6tm ext Table 9 3 shows a portion of this file The units of this file are reflectance 10000 Table 9 3 Jasper Image Target Reflectance File 7717 59 1171 09 1498 30 2196 30 3567 10 3194 80 Measured Target Reflectance Spectrum File This is the measured reflectance for the same target as the Image Target Reflectance Spectrum File The default location of the file for this tutor
50. e ehe ha EE Pe ER Eee ebbe een ad ede E Tcu 50 Other Tutorial Examples iie eat pe p pr ER spawn ee PEN PNEU UE KR Miser Ua davp E qus 50 Chapter 5 Mode 2 Single spectrum enhancement of a hyperspectral atmospheric correction Descriptions areri ie aE E e REAPER TE NET E t ees a ers 52 Input Image Data oiii e ee ea a ea AE tI ER TURA UD E A EE O TEA E Oa AEE Ge 52 Starting ACORN evt Gusset a rer p o E a pO EC E edad a a TAE EE nE ep SS 54 Reviewing and Editing the Control File lieet repetere ES Pa etae ERE dE o ep RUE 55 Running ACORN MDde 2 sten De tea er Ciel oc dde dise ean Jie se oa 57 ACORN Mode 2 Results eneen A EEE eset AAE E OAE E ASEN ees 58 Additional Output Files yas ses os ape rre Hier pus dae RENE Diete i ber EE eR ue De seus 59 Other T torial RAM ples o isce I te Ee EHE e Eo PO E te PT Rb PN E ER Eso dad ut 59 Chapter 6 Mode 3 Atmospheric correction using the empirical line method for hyperspectral data B reunir P n 62 Input Image Data io eere doe dei te t de ue tese tip it devi tosta dL 62 Start inp ACORN tsedisdip tque ve euius e Rd esa E pio MEDI EC NE NUR RS V E EA E TNE G Send 64 Reviewing and Editing the Control Hile seis cec cesi eee aes eee peau vu Vete un ce Er e ges 65 Running ACORN Mode 3 2 osito rues Qus au sostenuto Rev Seniesa Pone doas ANLE E 68 ACORN Mod 3 Results eerte eE eer Sesn aure se er e EA X ese Yee o o eus p EM EE ts 68 Additional Output Piles e O
51. e input parameters used in the atmospheric correction and indicates problems encountered during the run diag2 In the same directory as the output the jsp5tmrfl diag2 file will be created This file contains selected spectral outputs that may be helpful to understand problems with the convolution Other Tutorial Examples Additional tutorial examples are provided with ACORN for the Cuprite AVIRIS and Cuprite Hymap data The default location for these files is c Program Files ACORN4 Data Cuprite cup5 in and c Program Files ACORN4 Data Cupriteh cuph5 in You may run these examples and examine the input and output files to gain additional experience with ACORN mode 5 91 Chapter 9 Mode 6 Single spectrum enhancement of a multispectral atmospheric correction The following topics are covered in this chapter 92 DescripBolbs ooi co A E MM i E e Inpatinidse Data possess econ pet veda Rd creen EEE E e uere dnte c E CE A Starin t ACORN oU E M Reviewing and Editing the Control File eterni ore brodo ce led eee eda VERE Eg V Running ACORN Mode D ce eh ei d sa qeu ee deae rero de vitet l soe A sry peu ACORN Mode 6 R8SUITSS aio sesbob e Re EUR Ho a o e EE OP Ep EPE POET UH et Rb Ud Additional Output Piles a a cn t eee itd e cure RR Ead rre innt EE RON ELCHE Other Tutorial Examples ordei iiis eate ru orn rro tasas eae aee sas eu Yeu dante e nen eed e Ee NR IDE a 93 Description ACORN Mode 6 uses a set of bands extracted fr
52. eflectance data set 1 Start ACORN by selecting Start gt Programs gt ACORN4 gt ACORN The ACORN Control Panel will appear as shown in Figure 9 3 ACORN operates based on control files that provide the parameters and files for the ACORN algorithm 95 ACORN 4 tm Comet Panel F e Eda Run TransterLicense Help ACORN Con tie Aerie a Single Aun Smnory Processing Modo Osips Reterisnce mme File Name Aveileble Duk Space ior Cupit Fla amp Moves Figure 9 3 ACORN Control Panel Reviewing and Editing the Control File Note Except for the examples provided with ACORN you must obtain the appropriate calibration files and data parameters from the data provider 1 From the ACORN Control Panel select Open 2 For this example choose the Japser Ridge Mode 6 example control file The default installation location for this control file is C Program Files ACORN4 Data Jasper jsp6 in 3 Examine the ACORN control file parameter entry panel shown in Figure 9 4 These are the files and parameters necessary to perform the single spectrum enhancement to the atmospheric correction Each parameter and file is described below for this tutorial example 96 Mode 6 C Program Files ACORN4 Data Jasper jspt in xj Input Image File Nome Inout File Farmat Image Dimension EEE a 070000 0B 00 s ES riz l Output Reflectonce Image Fila Name Irhager Format He host intel 614 somples C network IEEE o ofset
53. extracted spectra may be saved to an ASCII file by selecting File gt Output Data gt ASCII EN ENVI Piot window STE File Edit Options Plot_Function 1 2X10 1 0 1 M 0x10 7 6 0x107 X 4 0x107 MAT Rd 3 4 Band Number 85 Figure 8 3 Extracted spectra from Jasper Ridge convolved mulitpsectral radiance image Table 8 1 Locations of Extracted Spectra Site Sample Line Stanford Golf Course 504 226 Jasper Ridge Grassland 314 159 Plowed Field 402 242 Redwood Forest 102 250 Felt Lake 398 355 These image radiance data contain the effects of the solar illumination two way transmittance and scattering of the atmosphere as well as reflectance of the surface These image extracted spectra are also scaled so that the radiance values fall in a range of efficiently stored integers ACORN Mode 5 is designed to correct for these illumination and atmospheric effects in Multispectral data Starting ACORN In this section ACORN Mode 5 will be used to atmospherically correct the Jasper Ridge calibrated multispectral radiance data set 1 Start ACORN by selecting Start gt Programs gt ACORN4 gt ACORN The ACORN Control Panel will appear as shown in Figure 8 4 ACORN operates based on control files that provide the parameters for atmospheric correction ACORN 4 te Commi Panel E NIE F e Eda Run Transfer License Heip ACORN Canta Pie amp amp 5 amp a 3 Snge Pun S amp umnery
54. f each mode in the ACORN User s Manual At present perfect calibration and perfect knowledge of the atmosphere are not achievable Some artifacts will be present in every atmospheric correction The strength of the artifacts will be related to the quality of the calibration the knowledge of the atmosphere and the ability to model the atmosphere Several options and modes are offered in ACORN to help suppress artifacts in the atmospheric correction Input Image Data For this example of ACORN mode 1 the AVIRIS data set acquired over Jasper Ridge California is used Begin by examining the Jasper Ridge calibrated radiance data set provided with the ACORN software 1 Start ENVI software on your computer 2 Open the Jasper Ridge data provide with ACORN The default installed location is c program files ACORN4 Data Jasper jspOrdn 3 Select bands 30 40 20 to display as red green blue This is done with in the Available Bands List window by clicking the RGB Color option and then scrolling and clicking on band 30 40 and 20 in that order Then click the Load Band button This image is shown in Figure 3 1 Figure 3 2 shows a set of extracted spectra from the Jasper Ridge data Table 3 1 gives the site and location of these extracted spectra 26 B 1 R Band 30 G Band 40 6 Band 20 jsp0rdn Figure 3 1 Jasper Ridge radiance image bands 30 40 and 20 as red green and blue 4 Extract and examine the radiance spectra with ENVI Z profile
55. files in the new window that you wish h These extracted spectra may be saved to an ASCII file by selecting File gt Output Data ASCII 54 Ini xj File Edit Options Plot Function 10000 BANN BUDD 1 0 0 AN OD My en c CUL Figure 4 2 Extracted spectra from Cuprite ACORN Mode 1 atmospherically corrected image Table 4 1 Locations of Extracted Spectra Site Sample Line Stonewall Playa 606 293 Opalite Zone w Alunite 554 272 Strongly Argillized Zone w Kaolinite 526 319 Buddingtonite Zone 472 235 Calcite 295 348 These extracted spectra from the Cuprite ACORN Mode 1 atmospherically corrected image have some spectra roughness to them across the spectral range This is due to imperfections in the data calibration as well as the atmospheric modeling used by ACORN ACORN Mode 2 is designed to suppress this systematic spectral roughness Starting ACORN In this example ACORN Mode 2 will be used to enhance the atmospheric correction for the Cuprite ACORN Mode 1 reflectance data set 1 Start ACORN by selecting Start Programs ACORNA ACORN The ACORN 4 Control Panel will appear as shown in Figure 5 3 ACORN operates based on control files that provide the parameters and files for the ACORN algorithm 55 ADORN 4 im Commi Panel F e Eda Hun TransterLicense Heip ACORN Conti tie Aerie a Single Aun Smnory Processing Modo ntpur Perle ctence mme File Name Aveileb
56. he dimensions of the Jasper Ridge data set are 224 bands 512 lines and 614 samples with 0 byte offset Image Spectral Calibration file This is the spectral calibration file for the input image The default location is C Program Files ACORN4 Data Jasper avr97 wvl This is a two column file The first column is the center position of each spectral band in the image in nanometers The second column is the full width at half maximum FWHM of the appropriate Gaussian function to describe the spectral response function of the band in nanometers Table 4 2 shows a subset of this file 45 Table 4 2 Jasper Ridge spectral calibration file 369 85 9 61 379 69 9 58 389 53 9 55 2486 99 10 07 2496 90 10 05 2506 81 10 03 Gain File This is the gain file that converts the image file integer values to radiance in units of W m42 um sr The default location is C Program Files ACORN4 Data Jasper avr97 gain This is a one column file that is multiplied by the image integer values to convert the integers to the correct radiance units Table 4 3 shows a subset of this file Table 4 3 Contents of the Jasper Ridge gain file 0 2 0 2 0 2 0 1 0 1 0 1 Offset File This is the offset file that corrects for any offset in the image file integer values in the conversion to radiance in units of W m 2 um sr The default location is C Program Files ACORN4 Data Jasper avr97 off This is a one column file that is added to the radiance values Tab
57. herically corrected Jasper Ridge image following implementation of ACORN mode 4 and Mode 5 4 Extract and examine the radiance spectra with ENVI Z profiles a This is done in the ENVI image window by selecting Functions gt Profiles gt Z Profiles 94 b To move the cursor to a specific location from the ENVI image window select Functions gt Interactive Analysis gt Pixel Locator c In the pixel locator window enter the X and Y location and click Apply d To extract and save spectra select Option New Window Blank e In the Z profile window click the right mouse button to show the X Y location of the displayed spectrum f To save a spectrum to the blank window drag X Y location label to the new window g Repeat this until you have all the Z profiles in the new window that you wish h These extracted spectra may be saved to an ASCII file by selecting File gt Output Data ASCII iol x File Edit Options Plot Function 4000 3000 2000 1000 Figure 9 2 Extracted spectra from Jasper Ridge data set after Mode 4 convolution to multispectral data and Mode 5 atmospheric correction Table 9 1 Locations of Extracted Spectra Site Sample Line Stanford Golf Course 504 226 Jasper Ridge Grassland 314 159 Plowed Field 402 242 Redwood Forest 102 250 Felt Lake 398 355 Starting ACORN In this example ACORN Mode 6 will be used to enhance the atmospheric correction for the Jasper Ridge Mode 4 and Mode 5 generated r
58. hese atmospheric effects Starting ACORN In this section ACORN Mode 1 will be used to atmospherically correct the Jasper Ridge calibrated radiance data set 1 Start ACORN by selecting Start Programs ACORNA ACORN The ACORN 4 Control Panel will appear as shown in Figure 3 3 ACORN operates based on control files that provide the parameters for atmospheric correction ACORN 4 tm Control Panel ell x F e Edt Run TransterLicense Help ACORN Con lie 2 a amp amp a Single Aun Sumner Proccts rg Modo Ostet Perle rtence megs File Name ean if amp Aveilable Cink Space tor Oui ut Fla ans Moves E 28 Figure 3 3 ACORN Control Panel Reviewing and Editing the Control File 1 Select Open 2 Select the Jasper Ridge mode 1 control file The default location for this file is C Program Files ACORN4 Data Jasper jspl in 3 Examine the ACORN Mode 1 control file parameter entry panel shown in Figure 3 4 These are the files and parameters necessary to perform a Mode 1 atmospheric correction Each parameter and file is described for the Jasper Ridge example Note Except for the examples provided with ACORN you must obtain the appropriate calibration files and data parameters from the data provider c Program Files ACORN4 Data Jasper jsp1 in BEES xl Input Image File Name r Input File Format Image Dimension CUENTEN bip C bil 224 bands C Program File CORN4 Data Jaspe r
59. ial is C Program Files ACORN4 Data Jasper jps6tm meas This is a two column file The first column is wavelength in nm and the second column is reflectance The reflectance is multiplied by 10000 to have the same scaling as the Image Target Reflectance Spectrum File Table 9 4 shows a portion of this file Table 9 4 Contents of the Measured Target Reflectance Spectrum File 350 250 02 351 251 14 352 253 81 2498 2573 75 2499 2574 65 2500 2575 773 98 Running ACORN Mode 6 To execute ACORN mode 6 click Run on the ACORN control panel A processing status box will appear to indicate the progress of the single spectrum enhancement When the processing is complete the program will return to the ACORN Control Panel ACORN Mode 6 Results The principal result of ACORN Mode 6 is the single spectrum enhanced reflectance image 1 With ENVI open the Jasper Ridge single spectrum enhanced image The default location for the tutorial is c program filesNACORNAMDataNJasperNVjsp6tmrfl Figure 9 5 shows the reflectance image with bands 3 4 2 displayed as Red Green Blue respectively 2 Extract the single spectrum enhanced spectra from the sites in table 9 1 The extracted spectra are shown in Figure 9 6 3 Compare the extracted single spectrum enhanced spectra with the input reflectance spectra in Figure 6 2 The radiative transfer code based reflectance has been enhanced to the accuracy of the surface reflectance spectrum of the target
60. ic correction and indicates problems encountered during the run diag2 In the same directory as the output reflectance the cup3rfl diag2 file will be created This file contains selected spectral outputs that may be helpful to understand problems with the atmospheric correction Other Tutorial Examples Additional tutorial examples are provided with ACORN for the Jasper Ridge AVIRIS and Cuprite Hymap data The default location for these files is c Program Files ACORN4 Data Jasper jsp3 in and c Program Files ACORN4 Data Cupriteh cuph3 in You may run these examples and examine the input and output files to gain additional experience with ACORN mode 3 71 Chapter 7 Mode 4 Convolution of hyperspectral data to multispectral data The following topics are covered in this chapter Desortptiolio cxi EYE eL ONU KUp Le aud es eyuMes nae du E EEEE NE EREE TEREE ET Input Image Data ccs ices vo i eH bias Inv Deu E oan bade gen ER D RR wien EERE NI FA DP eases Starting ACORN T daw Reviewing and Editing the Control File ice ree eee alee t RAP I egi vus Running ACORN Mode F res e nose pv ER een pte abor soto etna pna Hose Rope oo eps ed PESEE EYEE METS ACORN Mode Results uve er e s rt Ee ole eia dae redit epa Additional Output Files 5 2 i tex e t ee taxi ea Ea Da eee Tea ecu v Eb RE eus Other Tutorial Examples rte sess od RE IRE RE Ene OM EE M ds ae 12 713 Description ACORN uses the designated mult
61. is complete examine the Cuprite reflectance image 1 Start ENVI software 2 Open the Cuprite Nevada data provide with ACORN The default location for this data set is c Program Files ACORN4 Data Cuprite cupIirfl 3 Select bands 200 130 30 to display as red green blue This is done with in the Available Bands List window by clicking the RGB Color option and then scrolling and clicking on band 200 130 and 30 in that order Then click the Load Band button The resulting displayed image is shown in Figure 5 1 Figure 5 2 shows a set of extracted spectra the Cuprite atmospherically corrected data set Table 5 1 gives the site image label and location of these extracted spectra 53 D 1 R Band 200 G Band 138 8 Bend 30 cupi ni Figure 5 1 Cuprite Nevada AVIRIS radiance image 4 Extract and examine the radiance spectra with ENVI Z profiles a This is done in the ENVI image window by selecting Functions gt Profiles gt Z Profiles b To move the cursor to a specific location from the ENVI image window select Functions gt Interactive Analysis gt Pixel Locator c In the pixel locator window enter the X and Y location and click Apply d To extract and save spectra select Option New Window Blank e In the Z profile window click the right mouse button to show the X Y location of the displayed spectrum f To save a spectrum to the blank window drag X Y location label to the new window g Repeat this until you have all the Z pro
62. is is a two column ASCII file containing the multispectral spectral response functions The first column is the wavelength in nanometers and the second column is the response value for the multispectral band The spectral responses for each band are contained in this one file with the end of each band indicated by a negative value in the second column The default location of the file for this tutorial is 106 C Program Files ACORN4 Data Jasper tm rsp Table 10 2 shows a portion of the spectral response file Table 10 2 Mulispectral Spectral Response File 428 0 0000 430 0 0021 432 0 0087 434 0 0154 436 0 0221 500 0 979 502 0 9883 504 1 0000 506 0 9609 508 0 914 552 0 0003 554 0 0001 556 0 0001 502 0 0000 504 0 0006 506 0 0057 Dark Target Image Value File This is a single column file with the extracted values from the image jsp4tm that corresponds to the location where a accurate surface reflectance spectrum of a dark target has been acquired The default location of the file for this tutorial is C NProgram FilesNACORNANDataNJasperrNjsp7tmd ext Table 10 3 shows a portion of this file The units are the image value units Table 10 3 Jasper Image Dark Target File 6782 2 5066 2 3874 5 3076 0 507 2 154 9 Dark Target Reflectance Spectrum File This is the measure reflectance for the dark target The default location of the file for this tutorial is C Program Files ACORN4 Data Jasper jps7tmd meas This is a two col
63. ispectral spectral response functions to convolve a spectrally and radiometrically calibrated hyperspectral data set to the corresponding multispectral data set This convolution handles the case of overlapping or irregularly spaced sampling in the hyperspectral data set ACORN mode 4 requires input of a calibrated hyperspectral data set For the convolution the spectral response functions of the multispectral data set to be generated are required Figure 7 1 shows the spectral response functions for a six band multispectral sensor in the solar reflected spectrum Any multispectral data set may be generated that is within the spectral range of the hyperspectral data set Multispectral band response functions for existing planned or imagined multispectral sensors may be used Ki 1 0 9 2 0 8 Response S T T T T T T 400 700 1000 1300 1600 1900 2200 2500 Pp c o c nnn Normalized Res o T oo c N U Wavelength nm Figure 7 1 Multispectral spectral response functions for six bands in the solar reflected spectrum from 400 to 2500 nm Input Image Data For this example of ACORN mode 1 the AVIRIS data set acquired over Jasper Ridge California is used Begin by examining the Jasper Ridge calibrated radiance data set provided with the ACORN software 1 Start ENVI software on your computer 2 Open the Jasper Ridge data provide with ACORN The default installed location is c program files ACORN4 Data Jasper
64. isplayed as Red Green Blue respectively 89 2 Extract the atmospherically corrected spectra from the sites in table 8 1 The extracted spectra are shown in Figure 8 7 These spectra are stored as 2 byte integers of reflectance multiplied by 10000 This preserves the precision of the measurement and allows the data to be stored efficiently 3 Compare the extracted reflectance spectra with the input radiance spectra The effects of the solar source and atmosphere have been compensated E 1 Send 3 G Bend 4 6 Band 2 jsphtmrit Figure 8 6 Atmospherically corrected Jasper Ridge image following implementation of ACORN mode 5 EN ENVI Piot window STE File Edit Options Plot Function 2000 1000 Figure 8 7 Extracted spectra from Jasper Ridge data set after mode 1 atmospheric correction 90 Additional Output Files In addition to the output image file there are several other files created by ACORN in This is the control file that provides the files and parameters that are used by ACORN The file jsp5 in was created in the default location for this tutorial example eco In the same file location of the jsp5 in file will be a jsp5 in eco This file is an echo of the input file as it is being interpreted by the ACORN software If problems are detected interpreting the control file these will be indicated in this file diagl In the same directory as the output file will be a jsp5tmrfl diagl The diagl file confirms th
65. ith ENVI extract the spectra from the five sites given in Table 3 1 Figure 3 7 shows these extracted spectra In comparison to the spectra shown in Figure 3 6 many of the spectral artifacts have been suppressed ENVI Plot Window 4 n x File Edit Options Plot Function 10000 BAAN oULD 6000 4000 34 Figure 3 7 Atmospherically corrected spectra from Jasper Ridge with ACORN Mode I and artifact suppression type 1 Artifact Suppression Type 1 and 2 Artifact suppression type 2 attempts to address radiometric calibration mismatches between the image data set and the radiative transfer code model of the atmosphere For this example from the ACORN Control Panel select Open and open file jsplal in The default installation location for this file is c Program Files ACORN4 Data Jasper jspla2 in Notice that in the control file editor artifact type 1 and 2 are selected Click OK Click Run on the ACORN Control Panel When the run is complete open the output image file with ENVI The location and name for this file specifed in the tutorial example control file is c Program Files ACORN4 Data Jasper jspla2rfl With ENVI extract the spectra from the five sites given in Table 3 1 Figure 3 8 shows these extracted spectra In comparison to the spectra shown in Figure 3 6 and Figure 3 7 additional spectral artifacts have been suppressed ENVI Plot Window loj x File Edit Options Plot Function 1000 Ys UPS GULL
66. le 4 4 shows a subset of this file Table 4 4 Contents of the Jasper Ridge offest file 0 0 0 0 0 0 0 0 0 0 0 0 Image Latitude These are the central degrees minute seconds of the image data set Each parameter may be integer or decimal If decimal degrees are used the minutes and second field should be zero North latitude is positive The central latitude of the Jasper Ridge data set is 37 18 Image Longitude These are the central degrees minute seconds of the image data set Each parameter may be integer or decimal If decimal degrees are used the minutes and second field should be zero The central longitude of the Jasper Ridge data set is 122 3 East longitude is positive Image Date This is the date of image acquisition in day month year format This example data set was acquired on the 3 of April 1997 46 Image Time This is the nominal time of acquisition in hours minutes and seconds The time must be Greenwich Mean Time GMT Each parameter may be integer or decimal The example Jasper Ridge data set was acquired at 19 57 23 GMT Artifact Suppression This option allows selection of artifact suppression options 1 Artifact suppression type 1 attempts to address spectral calibration mismatches between the image data set and the radiative transfer code model of the atmosphere ii Artifact suppression type 2 attempts to address radiometric calibration mismatches between the image data set and the radiative tr
67. le Duk Space for Cupit Fla amp Moves Figure 5 3 ACORN Control Panel Reviewing and Editing the Control File Note Except for the examples provided with ACORN you must obtain the appropriate calibration files and data parameters from the data provider 1 From the ACORN Control Panel select Open 2 For this example choose the Cuprite Mode 2 tutorial control file The default installation location for this control file is C Program Files ACORN4 Data Cuprite cup2 in 3 Examine the ACORN control file parameter entry panel shown in Figure 5 4 These are the files and parameters necessary to perform the single spectrum enhancement tutorial example Each parameter and file is described below for this tutorial example 56 Mode 2 C Program Files ACORN4 Data Cuptite cup2 in i xj Input Image File Nome Input File Format Image Dimension EEE A 075 07080 0090 99 BEE iz Output Reflectonce Image Fila Name Irhager Format Ln host intel 614 somples C network IEEE o ofset c Program Files ACORNAVDatreNCuprtelcup di aj Mode 2 Specio Paremeters Image Targat Reflectenca K C4 Program Files vACORNAVDeisC cup ex Spectrum File value 1 Progam Fils yACORN I Daini Cunrite yupi a le Canoa Image Specral Calibraban Fie vainm tem nm C FProgram Filas ACORN Date Cupritet mr 7 4 le Measured Target Rollectance Speciram Fila Oo Progrnn FilesvACORHNA DeteCupnte cupz maas wA fnm value
68. lue respectively 2 Extract the empirical line corrected spectra from the sites in table 6 1 The extracted spectra are shown in Figure 6 7 3 Compare the extracted empirical line corrected spectra with the input image radiance spectra in Figure 6 3 The radiance data have been corrected to apparent surface reflectance Some residual artifacts remain near the water vapor bands because the empirical line correction assumes a homogenous atmosphere over the entire data set 69 Figure 6 6 Empirical line atmospheric correction image following use of ACORN Mode 3 i ENVI Plot Window EN jac xl File Edit Options Plot Function 5000 4000 Figure 6 7 Extracted spectra from Cuprite data set after Mode 3 empirical line atmospheric correction Additional Output Files In addition to the output image file there are several other files created by ACORN in This is the control file that provides the files and parameters that are used by ACORN The file cup3 in was created in the default location for this tutorial example 70 eco In the same file location of the cup3 in file will be a cup3 in eco This file is an echo of the input file as it is being interpreted by the ACORN software If problems are detected interpreting the control file these will be indicated in this file diagl In the same directory as the output reflectance file will be a cup3rfl diagl The diagl file confirms the input parameters used in the atmospher
69. mage 1 With ENVI open the Jasper Ridge reflectance image The location specified in the tutorial control file is c program files ACORN4 Data Jasper jsplrfl Figure 3 5 shows the reflectance image with bands 30 40 20 displayed as Red Green Blue respectively 2 Extract the atmospherically corrected spectra from the sites in table 3 1 The extracted spectra are shown in Figure 3 6 These spectra are stored as 2 byte integers of reflectance multiplied by 10000 This preserves the precision of the measurement and allows the data to be stored efficiently Using 4 byte real numbers would require twice the disk space 3 Compare the extracted reflectance spectra with the input radiance spectra The effects of the solar source and atmosphere have been compensated Residual spectral artifacts are present at spectral regions of strong atmospheric absorption Suppression strategies for these artifacts are discussed further along in this chapter Also the water vapor is not completely compensated over vegetation sites This is addressed in the chapter on ACORN mode 1 5 32 T E 2 R Band 30 G Band 40 6 Band 20 isptrt Ini xj File Edit Options Plot Function 1000 Wavelength Figure 3 6 Extracted spectra from Jasper Ridge data set after mode 1 atmospheric correction Additional Output Files In addition to the output image file there are several other files created by ACORN 33 in This is the control file that provides the
70. mage data are stored as big endian host intel or little endian network or IEEE The Jasper Ridge integer format is big endian Image Dimension These are the dimension of the input image in terms of bands lines samples and offset The offset parameter is the number of bytes used to skip any embedded image headers The dimensions of the Jasper Ridge data set are 224 bands 512 lines and 614 samples with 0 byte offset Image Spectral Calibration file This is the spectral calibration file for the input image The default location is C Program Files ACORN4 Data Jasper avr97 wvl This is a two column file The first column is the center position of each spectral band in the image in nanometers The second column is the full width at half maximum FWHM of the appropriate Gaussian function to describe the spectral response function of the band in nanometers Table 7 2 shows a subset of this file Table 7 2 Cuprite image spectral calibration file 369 85 9 61 379 69 9 58 389 53 9 55 2486 99 10 07 2496 90 10 05 2506 81 10 03 Hyperspectral Gain File This is the gain file that converts the image file integer values to radiance in units of W m 2 um sr For this tutorial example the default installation location is C NProgram Files ACORN4 Data Jasper avr97 gain This is a one column file that is multiplied by the image integer values to convert the integers to the correct radiance units Table 7 3 shows a subset of this file This gai
71. n factor is required to account changing gains across the spectrum before the convolution is applied Table 7 3 Contents of the Jasper Ridge gain file 0 2 0 2 0 2 0 1 0 1 0 1 Mulispectral Spectral Response File This is a two column ASCII file containing the multispectral spectral response functions The first column is the wavelength in nanometers and the second column is the response value for the multispectral band The spectral responses for each band are contained in this one file with the end of each band indicated by a negative value in the second column The default location of the file for this tutorial is C Program Files ACORN4 Data Jasper tm rsp Table 7 4 shows a portion of the spectral response file 78 Table 7 4 Mulispectral Spectral Response File 428 0 0000 430 0 0021 432 0 0087 504 1 0000 506 0 9609 508 0 914 552 0 0003 554 0 0001 556 0 0001 502 0 0000 504 0 0006 506 0 0057 Multispectral Gain File This is the gain file that converts the convolved image radiance values to integer values for the output file For this tutorial example the default installation location is C NProgram Files ACORN4 Data Jasper Jsp4tm gain Table 7 5 shows a subset of this file This gain factor is required to preserve the precision of the convolution in the output integer data Table 7 5 Multispectral Gain File 100 100 100 100 100 100 Running ACORN Mode 4 To execute ACORN Mode 4 click Run on the ACORN contr
72. nated by shape of the exo atmospheric solar spectrum and the two way transmittance of the atmosphere The shape of the surface reflectance is not apparent in the radiance spectrum Figure 2 3 shows the surface reflectance of stonewall playa For the purposes of this tutorial and ACORN software reflectance is a unitless parameter corresponding to the ratio of the upwelling radiance from a surface to the expected upwelling radiance from a perfectly reflecting perfectly Lambertian surface Stonewall Playa Reflectance 0 T T T T T T 400 700 1000 1300 1600 1900 2200 2500 Wavelength nm Figure 2 3 Reflectance spectrum from Stonewall Playa The x axis is in units of wavelength in units of nanometers The y axis is in units of reflectance The shape of the surface reflectance is related to the molecular and scattering composition of the surface To pursue surface related research and or applications with remote sensing data atmospheric correction is a critical step This is true for both hyperspectral and multispectral remote sensing measurements Components of the Measured Radiance The radiance measured by a remote sensing instrument begins with the energy from the sun Figure 2 4 shows a spectrum of the solar irradiance arriving at the top of the atmosphere This spectrum has the overall form of a Planck function at 6000 degrees K temperature Superimposed on this general form are the effects of the solar atmosphere and ra
73. nds lines samples and offset The offset parameter is the number of bytes used to skip any embedded image headers The dimensions of the Jasper Ridge data set are 6 bands 512 lines and 614 sample with 0 byte offset 87 Image Spectral Response File This is a two column ASCII file containing the multispectral spectral response functions The first column is the wavelength in nanometers and the second column is the response value for the multispectral band The spectral responses for each band are contained in this one file with the end of each band indicated by a negative value in the second column The default location of the file for this tutorial is C Program Files ACORN4 Data Jasper tm rsp Table 8 2 shows a portion of the spectral response file Table 8 2 Mulispectral Spectral Response File 428 0 0000 430 0 0021 432 0 0087 434 0 0154 436 0 0221 500 0 979 502 0 9883 504 1 0000 506 0 9609 508 0 914 552 0 0003 554 0 0001 556 0 0001 502 0 0000 504 0 0006 506 0 0057 Gain File This is the gain file that converts the image integer values to radiance W m 2 um sr For this tutorial example the default installation location is C NProgram Files ACORN4 Data Jasper Jsp5tm gain Table 8 3 shows a subset of this file Table 8 3 Multispectral Gain File 0 01 0 01 0 01 0 01 0 01 0 01 Offset File This is the offset file that corrects for any offset in the image file integer values in the conversion to radiance in uni
74. nese ssa ssevacesceidetes tase eee eswe nessa cgeuoes sea Wea ee Running ACORN Mode 2 iuo cocci nesir E NESET EEEE VoL eet ep PR E TEES ACORN Mode 2 Results iuit RE ERE Liga PUDE RE UpE SU E ELO eas Additional Output PHes uocis epr o RU tei oto ene sas i avy Eas Ra REPE voe eos er EET Other Tutorial Examples 35 3 7 d Ea o Eat E n ol d e d x Reed 52 Description For single spectrum enhancement of a hyperspectral atmospheric correction ACORN uses a spectrum extracted from an atmospherically corrected hyperspectral data set and an accurately known spectrum for the same target With these two spectra the full atmospherically corrected hyperspectral data set is corrected to the accuracy of the known spectrum ACORN accurately and automatically convolves the known spectrum to the spectral characteristics of the hyperspectral data set for this atmospheric correction enhancement This is a powerful method to compensate for residual errors in the hyperspectral atmospheric correction due to data calibration as well as atmospheric modeling Input Image Data For this example the AVIRIS data set acquired over Cuprite Nevada is used Begin by using ACORN Mode 1 to atmospherically correct the Cuprite data set Do this by following the ACORN Mode 1 tutorial but use the input control file for Cuprite The default installation location for the Cuprite control file is c Program Files ACORN4 Data Cuprite cupl in Once the Mode 1 atmospheric correction
75. nge of temperatures in the upper zones of the sun 15 2200 0 2000 0 1800 0 1600 0 1400 0 HM Top of the Atmosphere 1000 0 Irradiance 800 0 600 0 400 0 200 0 Irradiance W m 2 um 400 0 700 0 1000 0 1300 0 1600 0 1900 0 2200 0 2500 0 Wavelength nm Figure 2 4 Spectrum of the exo atmospheric solar irradiance In the passage from the top of the atmosphere to the surface and then to the remote sensing instrument energy is absorbed by the molecules and particles in the atmosphere Figure 2 5 shows a transmittance spectrum of the atmosphere for a path from the top of the atmosphere to the surface and to a remote sensing instrument Transmittance 0 1 9 Transmittance 0 0 T T 400 0 700 0 1000 0 1300 0 1600 0 1900 0 2200 0 2500 0 Wavelength nm Figure 2 5 Transmittance of the atmosphere The attenuation is due to the absorption and scattering of energy by the molecules and particles of the atmosphere The dominant absorber in the atmosphere is water vapor Figure 2 6 shows a series of transmittance spectra for different amounts of water vapor in the atmosphere Only the transmittance due to water vapor is shown The amount of water vapor is given in units of precipitable mm of water vapor This corresponds to the depth of the puddle of liquid water if the water vapor in the atmosphere was condensed 16 11 1 0 AV P PEIRET Y VW MANI N 0 9 08 d 07 S 2 06 E a 05 Ss
76. ns of the Landsat remote sensing instrument El 1 R Band 30 G Dand 40 6 Band 20 jspOrdn Figure 2 11 Image of Jasper Ridge California 19 20 140 120 4 Target 1 Target 2 E 100 4 Target 3 3 Target 4 e 80 4 E E o 604 8 a dje S 41 24 o 0 400 700 1000 1300 1600 1900 2200 2500 Wavelength nm Figure 2 12 Multispectral radiance measurements from Jasper Ridge through the Landsat spectral response functions 12000 10000 4 Target 1 Target 2 S 8000 Target 3 S Target 4 E 6000 4 s 9 z 2000 4 _ c 0 400 700 1000 1300 1600 1900 2200 2500 Wavelength nm Figure 2 13 Multispectral derived reflectance from Jasper Ridge after atmospheric correction with ACORN To compare and contrast multispectral and hyperspectral measurement types the corresponding plots for the same data set are given at the full spectral resolution of theAVIRIS hyperspectral sensor Figure 2 14 shows the spectral response function for the AVIRIS sensors from 400 to 1000 nm The full range is not shown because the plot becomes too compressed Figure 2 15 shows the upwelling radiance spectra for the targets in the Jasper Ridge California data set Figure 2 16 shows the corresponding reflectance spectra for these targets following atmospheric correction with ACORN The hyperspectral spectra show the full spectral signatures across the spectra range mea
77. o In the same file location of the jsp7 in file will be a jsp7 in eco This file is an echo of the input file as it is being interpreted by the ACORN software If problems are detected interpreting the control file these will be indicated in this file diagl In the same directory as the output file will be a jsp7tmrfl diagl The diagl file confirms the input parameters used in the atmospheric correction and indicates problems encountered during the run diag2 In the same directory as the output the jsp7tmrfl diag2 file will be created This file contains selected spectral outputs that may be helpful to understand problems with the convolution Other Tutorial Examples Additional tutorial examples are provided with ACORN for the Cuprite AVIRIS and Cuprite Hymap data The default location for these files is c Program Files ACORN4 Data Cuprite cup7 in and c Program Files ACORN4 Data Cupriteh cuph7 in You may run these examples and examine the input and output files to gain additional experience with ACORN mode 7
78. ol panel A processing status box will appear to indicate the progress of the atmospheric correction When the convolution is complete the program will return to the ACORN Control Panel ACORN Mode 4 Results The principal result of ACORN Mode 4 is the convolved image 1 With ENVI open the Jasper Ridge convolved image The default location for the tutorial is c program files ACORN4 Data Jasper jsp4tm Figure 7 6 shows the convolved image with bands 3 4 2 displayed as Red Green Blue respectively 2 Extract the convolved image spectra from the sites in table 7 1 These spectra are shown in Figure 7 7 3 Compare the extracted convolved spectra with the input spectra in Figure 7 3 The Hyperspectral data set has been converted to multispectral 79 Figure 7 6 Convolved image following use of ACORN Mode 4 lolx File Edit Options Plot_Function Figure 7 7 Extracted spectra from Jasper Ridge data set after Mode 4 convolution Additional Output Files In addition to the output image file there are several other files created by ACORN in This is the control file that provides the files and parameters that are used by ACORN The file jsp4 in was created in the default location for this tutorial example 80 eco In the same file location of the jsp4 in file will be a jsp4 in eco This file is an echo of the input file as it is being interpreted by the ACORN software If problems are detected interpreting the control
79. om an atmospherically corrected multispectral data set and an accurately known spectrum for the same target With the band values and spectrum the full atmospherically corrected multispectral data set is then corrected to the accuracy of the known spectrum ACORN accurately and automatically convolves the known spectrum to the spectral characteristics of the multispectral data set for this atmospheric correction enhancement Input Image Data For this example the AVIRIS data set acquired over Jasper Ridge that has been convolved to Landsat Thematic Mapper bands and atmospherically corrected is used The convolved and atmospherically corrected data set are created by using ACORN modes 4 and 5 as described in proceeding chapters of this tutorial Begin by examining the Jasper Ridge convolved multispectral atmospherically corrected data 1 Start ENVI software on your computer 2 Open the Jasper Ridge data The default location is c program files ACORN Data Jasper jsp5tmrfl 3 Select bands 3 4 2 to display as red green blue This is done with in the Available Bands List window by clicking the RGB Color option and then scrolling and clicking on band 3 4 and 2 in that order Then click the Load Band button This image is shown in Figure 9 1 Figure 9 2 shows a set of extracted spectra from the Jasper Ridge data Table 9 1 gives the site and location of these extracted spectra PARGA EIT 3 G Band 4 8 Band 2 jspStmet Figure 9 1 Atmosp
80. pectra The spectra must have equal or better spectral resolution and sampling than the hyperspectral data set The spectral range must be equal or greater as well Spectra from the corresponding areas of the hyperspectral data set must be extracted using an image processing software capability Figure 6 1 also shows the extracted dark and bright target image radiance spectra With these spectra and the spectral calibration parameters of the hyperspectral data set ACORN performs an empirical line atmospheric correction 12000 14000 7 10000 4 Dark Target Bright Target 12000 Dark Target Bright Target 8000 10000 7 6000 4 8000 4 Reflectance 10000 fon e i e 4000 7 Image Scaled Radiance 4000 7 2000 2000 4 de 0 0 T T T T T 4 T gt 400 700 1000 1300 1600 1900 2200 2500 400 700 1000 1300 1600 1900 2200 2500 Wavelength nm Wavelength nm Figure 6 1 Left dark and bright target measured spectra from the Cuprite area Right spectra for the dark and bright targets extracted from the Cuprite hyperspectral radiance data Input Image Data For this example the AVIRIS data set acquired over Cuprite Nevada is used Begin by examining the scaled radiance spectra of the cuprite data set 1 Start ENVI software 2 Open the Cuprite Nevada data provide with ACORN The default installation location for this data set is c Program FilesNACORNANDataNCupriteNcupOrdn 3 Select bands 2
81. por and liquid water in vegetation or water saturated soil on the surface This gives an improved estimation of water vapor for the atmospheric correction and provides a surface liquid water parameter data set that may be used to describe liquid water related properties of vegetation The derived atmospheric properties are used in conjunction with the other constraint parameters to correct for the effects of the atmosphere in the hyperspectral data set With an input of calibrated spectral radiance data ACORN produces an output of apparent surface reflectance The ACORN user controls the strategy for water vapor estimation artifact suppression and visibility constraint and estimation As always the quality of the atmospheric correction is closely tied to the quality of the calibration of the image data At present perfect calibration and perfect knowledge of the atmosphere are not achievable Some artifacts will be present in every atmospheric correction The strength of the artifacts will be related to the quality of the calibration the knowledge of the atmosphere and the ability to model the atmosphere Several options are offered in ACORN to help suppress artifacts in the atmospheric correction result Input Image Data For this example the AVIRIS data set acquired over Jasper Ridge California is used Begin by examining the Jasper Ridge calibrated radiance data set provided with the ACORN software 1 Start ENVI software 2 Open the Ja
82. re vete hy ee rx su o od eux ue ce Votes Ea e UR E Ver ees 31 ACORN Mode L Results esnan peo ides ont oE a eau Dd sud Ro ur Deas ARENE our Sa NEETA NE 31 Additional Output PIS esses Street td sepeser inosan ia ote caus tue dpa teterev tu dusk dy 32 Artifact Suppression Type 1 2er hese cece gon RI ab a nat RUPEE S eR d ED E PU RU UY 33 Artfact Suppression DLype land 2 2 5 teer oO c e et de bs ed 34 Artifact Suppression Type 1 2 and 3 ien os UE EE bot veda seed at 34 Visibility ESHHIatloD oi eoo e e ERA TREE E EE ER Pe eg a ea eek dared Sas 35 Other Tutorial Examples 0 eode Sube PEE edp aea a tare eh Ee loss ior sue obest 37 Chapter 4 Mode 1 5 Radiative transfer atmospheric correction of calibrated hyperspectral data with water vapor and liquid water spectral fitting Dascrrpiolicou soos ctt et edt ei ive eed Sith eee e o usto od EE payee Sid so datuL oda 40 Input Image Datart 2 eco ooh teret Dou ulti pa quee DataSets odes tu D DR dores 40 Saron ACORN Dn s td EL epe t Ute ELA usd E LEE 42 Reviewing and Editing the Control Pile 2g eese xp oo oue Nue bue yu ie Hop E NE SU Yea ERE 43 Running ACORN Mode 1 5 erai Le exer sos Ta dor set s E AEAEE see n EE ERREUR 46 Retlectance Resultsces desto o ete ILIUM NES aes 47 Water Vapor Images aos nae er Oe ee rds ide teal ord epee ede M alvbe dva e qd 48 Liquid Water Tn age ccs oc ie nudes roo cote eire RE cue eid eee iR EAE EREE Nee RENTET 49 Additional Output Piles zuo e etre LI Epor EO ER R
83. s a This is done in the ENVI image window by selecting Functions gt Profiles gt Z Profiles b To move the cursor to a specific location from the ENVI image window select Functions gt Interactive Analysis gt Pixel Locator c In the pixel locator window enter the X and Y location and click Apply d To extract and save spectra select Option gt New Window Blank e In the Z profile window click the right mouse button to show the X Y location of the displayed spectrum f To save a spectrum to the blank window drag X Y location label to the new window g Repeat this until you have all the Z profiles in the new window that you wish h These extracted spectra may be saved to an ASCII file by selecting File gt Output Data ASCII Table 3 1 Locations of Extracted Spectra Site Sample Line Stanford Golf Course 504 226 Jasper Ridge Grassland 314 159 Plowed Field 402 242 Redwood Forest 102 250 Felt Lake 398 355 27 ID x File Edit Options Plot Function 6066 4000 Figure 3 2 Extracted spectra from Jasper Ridge radiance image These image radiance spectra contain the effects of the solar illumination two way transmittance and scattering of the atmosphere as well as reflectance of the surface These image extracted spectra are also scaled so that the radiance values fall in a range of efficiently stored integers ACORN mode 1 is designed to use input and derived parameters to assess and correct for t
84. s Stade als de a er e 31 Additional Output Files 2 ri sa t te ta ea a X aes vee is cus 32 Artifact Suppression Type 1 4 ue DE ees osa ke enda m pe ead ee Le EN EE ON 33 Artifact Suppression Type T and Pisce dete cooape tv aui du du TREE Momdaseyanless 34 Artifact Suppression Type 1 2 and 3 aote ot ver UI od cashes eds ea 34 Visibility Estimation PR ua ees 35 Other Tutorial Examples oe re e o EE et eL e e Ea neers EEE NE 37 25 Description ACORN mode 1 uses radiative transfer calculations and the measured calibrated hyperspectral data to deduce a subset of the atmospheric effects present in the hyperspectral data set These derived atmospheric properties are used in conjunction with modeled atmospheric properties to correct for the atmosphere in the hyperspectral data set With an input of calibrated hyperspectral radiance data ACORN produces an output of apparent surface reflectance Note The hyperspectral data must be spectrally and radiometrically calibrated to use ACORN The ACORN user controls the strategy for water vapor estimation artifact suppression and visibility constraint and estimation The quality of the ACORN atmospheric correction is closely tied to the quality of the calibration of the image data For all of the modes of ACORN the spectral and radiometric calibration of the data must be accurate Partial exceptions to this rule exist and are indicated in the description o
85. s water vapor from the strength of the water vapor absorption band expressed in the radiance spectrum i none ii 820 water vapor band iii 940 water vapor band iv 1140 water vapor band v 940 and 1140 water vapor band For this example the option to use both the 940 and 1140 nm water vapor bands is selected Fixed Water Vapor If water vapor is not derived from the data themselves then a fixed water vapor amount is required in units of precipitable mm of water vapor A value of 10 precipitable mm is entered but this parameter will not be used because the derive water vapor option is engaged 3l Image Atmospheric Visibility This parameter controls the visibility of the atmospheric model used in the atmospheric correction A visibility of 60 km is entered for this example ACORN Estimated Visibility If selected ACORN will attempt to estimate the visibility from the data themselves This option is not selected for this example 4 Click OK to complete creation of ACORN mode 1 parameter file 5 From the ACORN control panel window click Save to save the control file Jsp1 in Running ACORN Mode 1 To execute ACORN mode 1 click Run on the ACORN control panel A processing status box will appear to indicate the progress of the atmospheric correction When the atmospheric correction is complete the program will return to the ACORN Control Panel ACORN Mode 1 Results The primary result of ACORN Mode 1 is the atmospherically corrected i
86. sibility of 60 km is entered for this example ACORN Estimated Visibility If selected ACORN will attempt to estimate the visibility from the data themselves This option is not selected for this example 4 Click OK to complete creation of ACORN control file 5 From the ACORN control panel window click Save to save the control file Jsp1_5a3 in Running ACORN Mode 1 5 To execute ACORN mode 1 5 click Run on the ACORN control panel A processing status box will appear to indicate the progress of the atmospheric correction When the atmospheric correction is complete the program will return to the ACORN Control Panel 47 Reflectance Results The primary result of ACORN Mode 1 5 is the atmospherically corrected apparent reflectance image 1 With ENVI open the Jasper Ridge reflectance image The default location is c program files ACORN4 Data Jasper jsp1_5a3rf1l Figure 4 5 shows the reflectance image with bands 30 40 20 displayed as Red Green Blue respectively 2 Extract the atmospherically corrected spectra from the sites in table 4 1 The extracted spectra are shown in Figure 4 6 These spectra are stored as integer of reflectance multiplied by 10000 This preserves the precision of the measurement and allows the data to be stored efficiently 3 Compare the extracted reflectance spectra with the input radiance spectra The effects of the solar source and atmosphere have been compensated The reflectance spectra are smooth over
87. sips Retectance mme File Name Aveileble Duk Space ior ug ur Fla amp Moves Figure 4 3 ACORN 4 Control Panel Reviewing and Editing the Control File Note Except for the examples provided with ACORN you must obtain the appropriate calibration files and data parameters from the data provider 1 From the ACORN Control Panel select Open 2 For this example select the Jasper Ridge mode 1 5 control file The default location for this file is C Program Files ACORN4 Data Jasper jspl_5a3 in 3 Examine the ACORN control file parameter entry panel shown in Figure 4 4 These are the files and parameters necessary to perform the atmospheric correction Each parameter and file is described below for this Jasper Ridge ACORN mode 1 5 example 44 Mode 1 5 Ci Program Files ACORN4 Data Jasper jspi_SaSan Input Image File Neme hput File Format Image Dimension a C bp bil fez bands nt Farmat y Ines Output Reflectance Imaga Fie Name leger Farm a host Arel fps semples aj C network IEEE fo ottset CAProgram Files ACORNA Data Jasperispl_Ssirl Mode 1 5 Specific Parameters Image Spectro Calibration UM PU File vvl nm fiminmy OP Togrom Files A CORN Dens Jasper wa OK xri aique c Progrom Files ACORNA Data Jospehows qain Gim 2m eri CAProgrom Files ACORN Data Jospenjsp1 of le le le li R Image Center Image Certer mage Mean Elevation Lettude Longitude
88. sper Ridge data provide with ACORN The default installation location for this data set is c Program FilesNACORNAMDataNJasperNjspOrdn 3 Select bands 30 40 20 to display as red green blue This is done with in the Available Bands List window by clicking the RGB Color option and then scrolling and clicking on band 30 40 and 20 in that order Then click the Load Band button The resulting displayed image is shown in Figure 4 1 Figure 4 2 shows a set of extracted spectra the Jasper Ridge data Table 4 1 gives the site and location of these extracted spectra 4l Figure 4 1 Jasper Ridge AVIRIS radiance image Figure 4 2 shows a set of extracted spectra the Jasper Ridge data Table 4 1 gives the site image label and location of these extracted spectra 4 Extract and examine the radiance spectra with ENVI Z profiles a This is done in the ENVI image window by selecting Functions gt Profiles gt Z Profiles b To move the cursor to a specific location from the ENVI image window select Functions gt Interactive Analysis gt Pixel Locator c In the pixel locator window enter the X and Y location and click Apply d To extract and save spectra select Option New Window Blank e In the Z profile window click the right mouse button to show the X Y location of the displayed spectrum f To save a spectrum to the blank window drag X Y location label to the new window g Repeat this until you have all the Z profiles in the new window that
89. sured 21 Response ege 04 AAAA UVULA AVUA VVAV UVUA 400 500 600 700 800 1000 Wavelength nm oO o o Oo e fi fi Normalized Response o a L Figure 2 14 Spectral response functions for the AVIRIS hyperspectral remote sensing instrument over the range from 400 to 1000 nm The full range is not shown due to plot compression Radiance W m 2 um sr 400 700 1000 1300 1600 1900 2200 2500 Wavelength nm Figure 2 15 Measured hyperspectral radiance spectra from the Jasper Ridge California AVIRIS data set 11000 10000 4 2000 Healthy grassland 8000 4 Soil 7000 Forest 6000 4 5000 4 4000 4 3000 4 2000 3 1000 4 0 400 700 1000 1300 1600 1900 2200 2500 Dry Grassland Reflectance 10000 Wavelength nm Figure 2 16 Hyperspectral derived reflectance spectra after use of ACORN atmospheric correction 22 23 24 Chapter 3 Mode 1 Radiative transfer atmospheric correction of calibrated hyperspectral data The following topics are covered in this chapter DGS CIOs e MC EE 25 Input Image Data cc cspersi oer e E c np t suse etuba uote eben ee dude codd kata uo ne ELE de 25 SEAT UU ACORN rc rousse ipi tru OMA Ace cM CU S E eh UN 27 Reviewing and Editing the Control Eie escort Lise eue trae ex o Fe ooo eda VERE RE V 28 Running ACORN Modes ssi iu edu i ER IRE REN enw p ERR ERI E EE Rete Eee ee 31 ACORN Mode 1 Results eer e ot Ee e
90. ter 9 Mode 6 Single spectrum enhancement of a multispectral atmospheric correction D script om P P M M 93 Input Image Pc PR erie seedeeysiukd setae bane ead ceed esse ede ee E EEEE RARAN 93 Starline ACORN ovis usas ages oui us e duse xe sang ine r Ee Ea KLSE On PENNE AEU EEO S a 94 Reviewing and Editing the Control Puls 22 casi aee eene teet or eR een n Enn es 95 Running ACORN Mode 630 2453 asset dum EI dag det EE Pee ee nev ee eee et iun 98 ACORN Mode 6 Results 2025502000606 seep EE tapas e aou E ead eyelet ese ins 98 Additional Output Files el eec rab niner irie eder dU La A C RM ep Eie DDR Us 99 Other Tutorial Examples cs cdeseesxessaso toss vee Frob eoe vasca p cupa e wes av Ln ee EOS ROCA VERE Qu E VEO EE 99 Chapter 10 Mode 7 Atmospheric correction by the empirical line method for multispectral data Ib ego 102 Input Image ads uso cock err coco tho o3 Den Fe FERE GRE EOD red ROO YE eS YE EEEE AE au eS Ee FR DARET ET yes 102 Staruns ACORN EUREN 103 Reviewing and Editing the Control Ele 2er E Pase eo poa badd e UII ER n esis eke 104 Running ACORN Mode Ferier obire eet vi erbe ae rea Rte do UR n Ens eagles LEA 107 ACORN Mode 7 Results ee deas MED RS Can n er oo ete oup edi uae Cte 107 Additional Output EMes tco i e haha eate bee ditur 108 Other Tutorial Examplesiousedii eoe oa ie Uo ape eR EE EL RUNE RAND E EEEREN EE a EET 109 Chapter 1 ACO
91. the tutorial Begin by examining the Jasper Ridge convolved multispectral calibrated radiance data 1 Start ENVI software on your computer 2 Open the Jasper Ridge data provide with ACORN The default location is c program files ACORN Data Jasper jsp5tm 3 Select bands 3 4 2 to display as red green blue This is done with in the Available Bands List window by clicking the RGB Color option and then scrolling and clicking on band 3 4 and 2 in that order Then click the Load Band button This image is shown in Figure 8 2 Figure 8 3 shows a set of extracted spectra from the Jasper Ridge data Table 8 1 gives the site and location of these extracted spectra 84 Figure 8 2 Jasper Ridge Multispectral convolved radiance image 4 Extract and examine the radiance spectra with ENVI Z profiles a This is done in the ENVI image window by selecting Functions gt Profiles gt Z Profiles b To move the cursor to a specific location from the ENVI image window select Functions gt Interactive Analysis gt Pixel Locator c In the pixel locator window enter the X and Y location and click Apply d To extract and save spectra select Option gt New Window Blank e In the Z profile window click the right mouse button to show the X Y location of the displayed spectrum f To save a spectrum to the blank window drag X Y location label to the new window g Repeat this until you have all the Z profiles in the new window that you wish h These
92. ts of W m 2 um sr For this example the default location is C Program Files ACORN4 Data Jasper jsp5tm off This is a one column file that is added to the radiance values Table 8 4 shows a subset of this file Table 8 4 Contents of the Jasper Ridge multispectral offest file 0 0 0 0 0 0 0 0 0 0 0 0 88 Image Latitude These are the degrees minute seconds of the image data set Each parameter may be integer or decimal If decimal degrees are used the minutes and second field should be zero North latitude is positive The approximate latitude of the Jasper Ridge data set is 37 18 Image Longitude These are the degrees minute seconds of the image data set Each parameter may be integer or decimal If decimal degrees are used the minutes and second field should be zero The approximate longitude of the Jasper Ridge data set is 122 3 East longitude is positive Image Date This is the date of image acquisition in day month and year format This example data set was acquired on the 3 of April 1997 Image Time This is the average time of acquisition in hours minutes and seconds The time must be Greenwich Mean Time GMT Each parameter may be integer or decimal The example Jasper Ridge data set was acquired at 19 57 23 GMT Image Elevation This is the average elevation of the surface in the input image in meters The approximate elevation of the Jasper Ridge example data set is 200 m Image Acquisition Altitude
93. umn file The first column is wavelength in nm and the second column is reflectance The reflectance is multiplied by 10000 so that the output file will have this scale Table 10 4 Contents of the Dark Target Reflectance Spectrum File 350 400 03 351 402 22 352 407 38 2498 686 61 2499 685 99 2500 685 38 107 Bright Target Image Value File This is a single column file with the extracted values from the image jsp4tm that corresponds to the location where a accurate surface reflectance spectrum of a bright target has been acquired The default location of the file for this tutorial is C NProgram FilesNACORNANDataNJasperrNjsp7tmd ext Table 10 5 shows a portion of this file The units are the image value units Table 10 5 Jasper Image Bright Target File 23062 2 22706 1 20291 2 14731 5 2494 4 757 9 Bright Target Reflectance Spectrum File This is the measure reflectance for the bright target The default location of the file for this tutorial is C Program Files ACORN4 Data Jasper jps7tmb meas This is a two column file The first column is wavelength in nm and the second column is reflectance The reflectance is multiplied by 10000 so that the output file will have this scale Table 10 6 shows a portion of this file Table 10 6 Contents of the Bright Target Reflectance Spectrum File 350 1920 492 351 1928 312 352 1946 853 2498 3249 936 2499 3246 004 2500 3242 096 Running ACORN Mode 7 To execut
94. vegetation in the 980 and 1200 nm region where liquid water absorption in vegetation occurs LI 1 2 Bond 4 G Bord 40 amp Band 20 jsp1_ RE Figure 4 5 Atmospherically corrected Jasper Ridge image following use of ACORN mode 1 5 48 In x File Edit Options Plot Function 5000 4000 3000 Figure 4 6 Extracted spectra from Jasper Ridge data set after mode 1 5 atmospheric correction Water Vapor Image In addition to the atmospherically corrected reflectance image at water vapor image is generated from the spectral fitting algorithm Figure 4 7 shows the water vapor image for this tutorial example Water vapor is reported in units of precipitable microns um 1 With ENVI open the Jasper Ridge water image The default location is c program files ACORN4 Data Jasper jspl_5a3rfl wtrv 2 Use the ENVI cursor value location capability to examine the water vapor values From the ENVI image window select Function gt Interactive Analysis gt Cusor Location Value Move the cursor to various parts of the image to see the change in water vapor Water vapor varies from 5000 um to 7000 precipitable um 5 to 7 precipitable mm across the image This is a dry atmosphere data set The image is largely devoid of surface structure as expected for water vapor Some surface leakage occurs over dark targets such as the open water areas of lakes 49 Figure 4 7 Water vapor image from ACORN atmospheric correction mode 1 5 Liquid
95. with ACORN you must obtain the appropriate calibration files and data parameters from the data provider 1 From the ACORN Control Panel select Open 2 For this example choose the Cuprite Mode 3 tutorial control file The default installation location for this control file is C Program Files ACORN4 Data Cuprite cup3 in 3 Examine the ACORN control file parameter entry panel shown in Figure 6 5 These are the files and parameters necessary to perform the empirical line atmospheric correction Each parameter and file is described below for this tutorial example 66 Mode 3 C Program Files ACORN4 Data Cuptite cup in j Input Image File Nome Inout File Format Image Dimension a 02 05 050 5 09 Irbecyer Formal az lines host Intel 614 somples C network IEEE o ofset Output Reflectence Image File Name C Program Files ACOAN4 Deta Cuprite cup3il Qa Mode J Spectic Porarneters Image Spectral Calibration CA Pragi esvACORNAYDetesCuprtes o7 w File wvl nmi hii C Progrom FilessACORHASDotes Cuprkes 37 w OF Cancel d Dork Taget Image Spain File fusius C Program Filas Y ACORNADetet Cupriehcug Jd ens Dark Target Rellectance File dinm n CA Program Files ACORN4 Dete Cuprte cup3d meas Brighi Terget Image C Program Files amp 4COF H4sD etel Quorte cup Jb ext Spectrum File valua 99 uprte cur ep le i sis Rho Reka at C Program Files ACORN4 Dete Cuprte

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