Hello! It's me again :)
> If you go all the way from DN to Top-of-Atmosphere reflectances (via
> i.landsat.toar), then to Top-of-Canopy (via i.atcorr), you'll have
> floating point values ranging in [0, 1.0]. If you recode this back to
> 8-bit,
> you should consider whether there is an important loss of the
> radiometric resolution.
>
> So, recoding to another range is different than converting to integer
> numbers and trying to preserve the range.
The thing that worries me is that I don't know how to check if the loss of the radiometric resolution is important :/ What should I compare?
I was trying to convert to integer through r.mapcalc (the only other way I've found) with the function int(x) and x was my map (I hope it was ok to put map instead of x) but the result was a map with "one shade" of grey, so maybe it was wrong to put a map instead of x...
According to i.atcorr there is an option "output raster map as integer" (i), so if my input file will be _toar2@konfa (float) and I check that option I will have a map with integer values, right?
However, the most confusing thing for me with i.atcorr is "the aerosol optical depth". I don't have "meteorological parameter visibility". I have images from 1984 and 2007. I've found files for Global Aerosol Climatology (1981-2006) on this website http://gacp.giss.nasa.gov/data_sets/ I've found the proper row and column in the asci format, but they don't have data for
2007. I was trying to find it on different pages http://modis-atmos.gsfc.nasa.gov/MOD04_L2/acquiring.html but areas of my interest are black - so no data. On your page github with i.landsat.toar and i.atcorr you wrote "the value for aerosols optical depth (AOD), is set to 0.111 for winter and 0.222 for summer aquisitions" Are these default values? For DOS methods?
Can I use i.landsat.toar with DOS3 instead of i.atcorr? The others where using this http://gis.stackexchange.com/questions/126742/which-dos-method-use-to-convert-at-sensor-radiance-to-at-surface-values-in-grass And also on your graph (the one on github) Nikos, this DOS method leads to "corrected" reflectance. So it means that I can omit i.atccor, right? I'm thinking about preprocessing of my images like this: i.landsat.toar + DOS3, then r.recode (I don't know the other way to change float to integer), then i.histo.match And after that classification (I want to compare land change cover, it is Syrian Jezirah, so +/-95% is agriculture).
Greetings
Joanna
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