[GRASS-user] spatial connectivity function
Dylan Beaudette
debeaudette at ucdavis.edu
Fri Nov 20 13:41:11 EST 2009
Greetings,
We are trying to calculate hydrologic connectivity for a 33ha catchment based
on a an interpolated raster from a series of 100 spatially distributed soil
moisture measurements. Ideally, we would like to use the methods outlined (in
pseudo-code) here:
ftp://ftp.agu.org/apend/wr/2000WR900241/Psuedo_code.txt
It looks like step 1 (thresholding the data) can be done with r.mapcalc. Step
2 (label the connected regions) can be accomplished with r.clump. Now we are
stuck on step 3a (calculate the omnidirectional connectivity function) which
is some kind of estimate of linear 'connectivity'. Are there any modules that
can approximate this type of analysis, or is this going to require a new
module?
Here is a sample dataset that approximates what we are working with
# generate a fake, spatially-correlated field
r.surf.fractal out=fract dimension=2.8
# convert to indicators
r.mapcalc "fract.ind = if(fract > 0, 1, 2)"
# form spatially-connected 'clumps'
r.clump in=fract.ind out=fract.clump
Cheers,
Dylan
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