[GRASS-user] Re: Limit r.fillnulls to interpolate only small gaps

kaipi mapcollect at gmx.net
Wed Feb 23 08:33:28 EST 2011

Thanks for your help !

I tried the r.grow method and it works fine for me. The only problem that
remains is that r.fillnulls takes very long. Let me show you my workflow
with an SRTM tile as example:

r.in.srtm input=S50W075.hgt output=srtm 
g.region rast=srtm
g.region res=00:00:03
r.grow input=srtm output=srtm_grow radius=10 new=9000 
r.mapcalc "MASK=if(isnull(srtm_grow),0,1)"
r.fillnulls input=srtm output=srtm_filled_mask 

r.fillnulls takes 19 minutes to process on Windows. (Grass 6.4 on Vista64,
i7 920 with 12GB RAM). The CPU usage is only 13% (of one core) and memory
usage is about 77 MB. Even if I put the Grass workspace on a RAM-Disk I have
no signifikant performance improvement.
On Ubuntu (same hardware) processing time for r.fillnulls is 17:30 min using
100% of one CPU core and 100MB RAM.

Any ideas how I can speed up the process ?


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