On 17/05/17 12:07, Johannes Radinger wrote:
Hi,
I'd like to identify the cell of maximum flow accumulation for each
subbasin.
For example, I have a cover raster map representing all my subbasins
(each subbasin has its own cat value). Additionally, I have a flow
accumulation map. Now, I'd like to get a map with cells that are
actually those with the largest flow accumulation per subbasin (all
other cell should be NULL). I guess, using r.stats.zonal/r.statistics I
can identify the maximum flow accumulation value for each subbasin, but
this doesn't provide me a map with the corresponding cells!? Is there a
straight forward way to do that in GRASS with e.g. the mapcalc? Or do I
need to loop over each subbasin?
Somthing like this might work:
r.stats.zonal cover=bassins base=accumulation output=maxval
r.mapcalc maxpixels = "if(accumulation < maxval+epsilon && accumulation
> maxval - epsilon, 1, null())
The use of an epsilon value is to avoid difficulties of determining
floating point number equalities.
Moritz
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