[GRASS-user] Patching rasters based on other rasters

[Ken Mankoff]

Thanks. That helps. I now use the output of that (SZA_lut) and the
following:

r.mapcalc --o <<EOF
eval(SZA0 = if(SZA_lut == 0, ${img_arr[0]}), \
     SZA1 = if(SZA_lut == 1, ${img_arr[1]}), \
     SZA2 = if(SZA_lut == 2, ${img_arr[2]}), \
     SZA3 = if(SZA_lut == 3, ${img_arr[3]}), \
     SZA4 = if(SZA_lut == 4, ${img_arr[4]}), \
     SZA5 = if(SZA_lut == 5, ${img_arr[5]}))
SZA_min = SZA0+SZA1+SZA2+SZA3+SZA4+SZA5
EOF

  -k.


On Tue, Oct 17, 2017 at 1:41 PM, Moritz Lennert <
mlennert at club.worldonline.be> wrote:

>
>
> 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.
> >
> >_______________________________________________
> >grass-user mailing list
> >grass-user at lists.osgeo.org
> >https://lists.osgeo.org/mailman/listinfo/grass-user
>
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