| 03 Oct 2012 05:31 PM |
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Hello, i am new ENVI user, and I am trying to use FLAASH module on RapidEye L3A image, but the results aren´t good, but I am not sure about the wavelengths and fwhm values because I haven't found the values
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;ENVI FLAASH PARAMETERS TEMPLATE (4.7)
;Written Tue Oct 02 22:35:52 2012
;
; Project Parameters
enviacc.prj.radiance_file = C:\MONOGRAFIA C\ENVI2\62626
enviacc.prj.reflect_file = C:\MONOGRAFIA C\ENVI3\62626AC
enviacc.prj.filter_func_file = C:\Program Files\ITT\IDL71\products\envi47\filt_func\rapideye.sli
enviacc.prj.filter_func_file_index = 0
enviacc.prj.water_band_choice = 1.13
enviacc.prj.red_channel = 3
enviacc.prj.green_channel = 2
enviacc.prj.blue_channel = 1
enviacc.prj.water_abs_channel = 0
enviacc.prj.water_ref_channel = 0
enviacc.prj.kt_upper_channel = 0
enviacc.prj.kt_lower_channel = 3
enviacc.prj.kt_cutoff = 0.1000
enviacc.prj.kt_ratio = 0.4500
enviacc.prj.cirrus_channel = 0
enviacc.prj.water_retrieval = 0
enviacc.prj.modtran_directory = C:\Program Files\ITT\IDL71\lib\hook\
;
; MODTRAN Parameters
enviacc.modtran.visvalue = 40.0000
enviacc.modtran.f_resolution = 15.0000
enviacc.modtran.day = 14
enviacc.modtran.month = 1
enviacc.modtran.year = 2022
enviacc.modtran.gmt = 16.4406
enviacc.modtran.latitude = 10.5299
enviacc.modtran.longitude = -75.1097
enviacc.modtran.sensor_altitude = 630.0000
enviacc.modtran.ground_elevation = 0.0000
enviacc.modtran.view_zenith_angle = 170.1832
enviacc.modtran.view_azimuth = -88.1200
enviacc.modtran.atmosphere_model = 1
enviacc.modtran.aerosol_model = 1
enviacc.modtran.multiscatter_model = 2
enviacc.modtran.disort_streams = 8
enviacc.modtran.co2mix = 390.0000
enviacc.modtran.water_column_multiplier = 1.0000
;
; Image Parameters
enviacc.img.nspatial = 5000
enviacc.img.nlines = 5000
enviacc.img.data_type = 12
enviacc.img.margin1 = 0
enviacc.img.margin2 = 0
enviacc.img.nskip = 0
enviacc.img.pixel_size = 5.0000
enviacc.img.sensor_name = UNKNOWN-MSI
;
; Analysis Parameters
enviacc.ana.aerosol_scaleht = 1.5000
enviacc.ana.use_adjacency = 0
enviacc.ana.output_scale = 10000.0000
enviacc.ana.polishing_res = 0
enviacc.ana.aerosol_retrieval = 0
enviacc.ana.calc_wl_correction = 0
enviacc.ana.reuse_modtran_calcs = 0
enviacc.ana.use_square_slit_function = 0
enviacc.ana.convolution_method = fft
enviacc.ana.use_tiling = 1
enviacc.ana.tile_size = 100.0000
;
; Spectral Parameters
enviacc.spc.wavelength_units = nanometer
enviacc.spc.lambda = [
475.0000, 555.0000, 657.5000, 710.0000, 805.0000]
enviacc.spc.fwhm = [
-1.000000, -1.000000, -1.000000, -1.000000, -1.000000]
enviacc.img.p_input_scale = [
10.0000, 10.0000, 10.0000, 10.0000, 10.0000]
Please Help me, Any advice would be greatly appreciated.
Thank you
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MariM
Veteran Member
Posts:2396  
| 04 Oct 2012 08:28 AM |
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A quick Google search for 'rapideye l3a' provides many good links to find characteristics of Rapideye. According to this document, http://www.rapideye.com/u...cifications_ENG.pdf, you need to apply the 'radiometricScaleFactor' supplied in the XML file to first convert the data to radiance in units of "1/100th of a Watt/m2 sr-1 μm-1". When you input your data to FLAASH, you will need to provide a scale factor that converts this unit to uW/cm^2*sr*nm.
An incorrect assumption about the units of the data can cause poor and unexpected results. You don't need the FWHM to correct the data. If they are not supplied, ENVI will assume a Gaussian response function. |
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Deleted User
New Member
Posts: 
| 04 Oct 2012 08:59 PM |
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Hello, thanks for your help, i saw this document before. I converted the scale factor in the units μW/(cm^2*sr*nm) and the result was 0,001 but the atmospheric correction wasn't good.
I dont know if the problem is about RapidEye Image, because RAPIDEYE LEVEL 3A have Radiometric, sensor and geometric corrections, and this image is ready for to process. I need to do a multitemporal analisis, and the atmospheric correction is necesary, but i couldn't do it
Sorry for my language mistake. English is not my native language
Thank you
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MariM
Veteran Member
Posts:2396
| 05 Oct 2012 01:28 PM |
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A radiometric correction is not an atmospheric correction so you should probably still perform this step if you need to compare imagery from different dates.
I am not sure what you mean by "I converted the scale factor in the units μW/(cm^2*sr*nm) and the result was 0,001 but the atmospheric correction wasn't good." The FLAASH template shows your data is stored as integer so this would not be floating point radiance in those units. What do you mean by "the result was 0,001"?
If you are unsure of the parameters to use in FLAASH, Quac is a very good alternative. Just be sure to include a mask file if you have background in your image.
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Deleted User
New Member
Posts:
| 07 Oct 2012 06:59 PM |
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Hi, Thanks for your help.
Yes, I would have to do the atmospheric correction. I asked to another person and told me that this correction is impossible for RapidEye L3A, but I want to try.
I want to said that the scale factor of Radiance in RapidEye is 0,01 W/m2 sr μm, and the conversion in the ENVI units are 0,001 μW/cm^2*sr*nm, it is correct? , but I saw in other forum that this value is 10
I tried many times, but I don’t have good results. First I applied the scale factor to the data by Gain and Offset tool with Gain = 0.01 for to convert DN to float point radiance
And after I did the atmospheric correction in FLAASH using the scale factor 10, in the result some DN values are in negative, this is impossible for this reason is wrong
The last try, I did in QUAC and the same problem with negative DN values
Thank you
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Deleted User
New Member
Posts:
| 10 Oct 2012 06:30 AM |
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Hi MariM,
Did you have any experiences fail to operate Flaash?Because I have tried many times to run flaash on my Landsat imagery but ENVI will turn it off in the middle of processing.
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MariM
Veteran Member
Posts:2396
| 10 Oct 2012 09:05 AM |
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What will "turn off"? Are you saying ENVI crashes? That obviously would not be expected. You may have something wrong with your installation.
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