[GRASS-dev] spatial connectivity function

Dylan Beaudette debeaudette at ucdavis.edu
Fri Nov 20 13:41:11 EST 2009


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:


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 

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


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