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

[Rich Shepard]

On Sat, 7 Apr 2012, Micha Silver wrote:

> Maybe the MASK is somehow interfereing   ??

Micha,

   I wondered about this. The unweighted accumulation map does not generate
the error, yet the same mask is applied. But, this may be why the weighted
accumulation map does not throw an error if the entire elevation map is the
analytical unit.

   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.

Thanks,

Rich