[GRASS-user] Patching rasters based on other rasters

[Moritz Lennert]

Le 17 octobre 2017 13:38:34 GMT+02:00, Ken Mankoff <mankoff at gmail.com> a écrit :
>Dear GRASS List,
>
>I'm trying to do something in GRASS and can't figure out an efficient
>way to do it. I'm guessing it is possible with 1-3 lines, but don't
>know which ones. The algorithm I'm developing would be much more
>complex, and I hope someone can suggest a shortcut.
>
>I have several satellite products of the same region each day. For
>simplicity sake lets assume 3 overlapping solar zenith angle (SZA)
>products, and for each of those a visual image (VIS). I'd like to have
>one visual raster that, for each pixel, has the minimum SZA.
>
>I can get the minimum SZA for each pixel with
>
>r.mapcalc "SZA_min = min(SZA1,SZA2,SZA3)"
>
>But now I've lost the source of the minimum SZA, and I need it to link
>SZA1 with VIS1. 
>
>I could encode categories for each SZA:
>r.category map=SZA1 cats=0-360 values=1
>r.category map=SZA2 cats=0-360 values=2
>r.category map=SZA3 cats=0-360 values=3
>
>And then 
>
>r.mapcalc "SZA_min_cat = min(@SZA1, at SZA2, at SZA3)"
>
>And then use SZA_min_cat (values: 1 to 3) as a lookup to
>VIS1,VIS2,VIS3. I'm actually not clear how to do this last step, if
>this is the correct approach. Do I return to r.mapcalc, or is r.univar
>the right tool? 
>
>Any help will be much appreciated.

Check r.series, notably the min_raster method.

Moritz


>
>Thanks,
>
>  -k.
>  
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