Dear mailing list,
Apologies I am a new user with GRASS and have searched everywhere online for help with this but to no avail…
I’m trying to run the i.atcorr module on GRASS (version 6.4.3 on a Macbook Pro, Mavericks OSX) with Landsat8 imagery.
Parameters didn’t seem to be loading from the provided metadata file (MTL_txt) (basically what happened is that when the code was executed it wasn’t picking up any of the parameters from the text file), so I went back to the GRASS manuals and tried to input values by hand, here is what I used:
8 = geometrical conditions=Landsat ETM+
05 04 03.81 98.117 23.131 = month day hh.ddd longitude latitude (“hh.ddd” is in GMT decimal hours)
1 = atmospheric mode=tropical
0 = aerosols model=none (ASSUMING NO AEROSOLS)
0 = visibility [km]
0.732 = aerosol optical depth 550 nm
-1.408 = mean target elevation above sea level [km]
-1000 = sensor on board a satellite
0 = THIS IS WHAT I’M WORRIED ABOUT: There is no pre-defined coding for Landsat 8 satellites and I am unsure how to define my own spectral conditions??
I checked I was in the correct region (i.e. used g.region) and I’ve tried using both radiance and reflectance at sensor values (computed using i.landsat.toar, which seems to have worked nicely) but the rasters returned are empty 
Here is what I’m running (in verbose)
i.atcorr -a --overwrite --verbose iimg=Part1toar_B1@Charlie icnd=/Users/charlottewhitham/Documents/PhD/My research/my GIS/grassdata/NGH/Charlie/.tmp/Charlie.local/819.2 oimg=P1toar_atcorrB1 * ******** 6s version 4.2b
- geometrical conditions identity *
- ------------------------------- *
- etm+ observation * * *
- month: 5 day: 4 *
- solar zenith angle: 23.55 deg solar azimuthal angle: 103.24 deg *
- view zenith angle: 0.00 deg view azimuthal angle: 0.00 deg *
- scattering angle: 156.45 deg azimuthal angle difference: 103.24 deg * * *
- atmospheric model description *
- ----------------------------- *
- atmospheric model identity : *
- tropical (uh2o=4.12g/cm2,uo3 =.247cm-atm) * * *
- aerosols type identity : *
- no aerosols computed * * *
- spectral condition *
- ------------------ *
- constant *
- value of filter function : *
- wl inf=27640754752056197120.000 mic wl sup= 0.000 mic * * *
- target type *
- ----------- *
- homogeneous ground *
- constant reflectance over the spectra 0.000 * * *
- target elevation description *
- ---------------------------- *
- ground pressure [mb] 862.22 *
- ground altitude [km] 1.408 *
- gaseous content at target level: *
- uh2o= 2.056 g/cm2 uo3= 0.244 cm-atm * * *
- atmospheric correction activated *
- -------------------------------- * Atmospheric correction… Atmospheric correction complete. (Fri Dec 6 12:16:10 2013) Command finished (22 sec)
And here is the output:
| Layer: P1toar_atcorrB1@Charlie Date: Fri Dec 6 12:12:58 2013 | | Mapset: Charlie Login of Creator: charlottewhitha | | Location: NGH | | DataBase: /Users/charlottewhitham/Documents/PhD/My research/my GIS/grassda | | Title: ( P1toar_atcorrB1 ) | | Timestamp: none | |----------------------------------------------------------------------------| | | | Type of Map: raster Number of Categories: 0 | | Data Type: CELL | | Rows: 7381 | | Columns: 7551 | | Total Cells: 55733931 | | Projection: UTM (zone 47) | | N: 2666715 S: 2445285 Res: 30 | | E: 522315 W: 295785 Res: 30 | | Range of data: min = NULL max = NULL | | | | Data Description: | | generated by i.atcorr | | | | Comments: | | i.atcorr -a iimg=“Part1toar_B1@Charlie” iscl=0,255 icnd=“/Users/char\ | | lottewhitham/Documents/PhD/My research/my GIS/grassdata/NGH/Charlie/\ | | icnd_lsat1.rtf” oimg=“P1toar_atcorrB1” oscl=0,255
As you can see the range of data is NULL to NULL… not good.
I would be very grateful if somebody could please help me with this - I’m really unsure what to try next and I’m running out of time!
Thank you very much in advance and please let me know if I need to provide more info,
Cheers, Charlie