[GRASS-user] Re: r.stream.extract Syntax Problem

[Helmut Kudrnovsky]

> Each of my two current projects requiring spatial analyses involve
>multiple 12-digit HUC basins (sub-watersheds). I need to separately analyze
>each sub-watershed to determine differences. I can clip vector maps by
>interescting the lines and the sub-watershed boundaries. But, my
>understanding is that raster maps cannot be subdivided in the same way so
>we need to generate masks for the areas to be included in each analysis.
>That is, r.* modules are applied to only those portions of the overall DEM
>map within the mask.
>
>   If there is a module, or process (perhaps applying r.mapcalc for the map
>algebra), that will allow me to create separate DEMs for each sub-watershed
>(or other analytical unit) I would prefer to work with each of those rather
>than need to run r.mask for each different basin. I'd like to learn how to
>sub-set raster DEMs so each basin is a separate map rather than a masked
>portion. 

if the (sub-)watershed are already given, maybe the easiest way to define
the region extent for raster processing of your interest is using g.region
[1]:

'g.region -a rast=yourdem align=yourdem vect=subbasin1'

raster processing

'g.region -a rast=yourdem align=yourdem vect=subbasin2'

raster processing

etc.

no need to create separate DEMs for each sub-watershed (or other analytical
units) or masks.

Helmut

[1] http://grass.osgeo.org/grass64/manuals/html64_user/g.region.html




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best regards
Helmut
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