id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,cpu,platform 2016,v.surf.idw: very incorrect results,hamish,grass-dev@…,"Hi, I have noticed with some data very bad results with v.surf.idw. The r.surf.idw and r.surf.idw2 modules do ok with the same data after v.to.rast of the starting points. But the v.surf.idw results are not realistic both spatially and numerically. In my real data I was seeing bad slivering between sample sites, but can recreate other little-relation to source data weirdness with synthetic input. commands to make the attached screenshot in grass6: {{{ g.region -d # spearfish # from addons: r.surf.volcano out=gauss method=gaussian kurtosis=0.5 peak=5000 r.random in=gauss vect=gauss_rand_500 n=500 v.surf.idw in=gauss_rand_500 out=gauss_rand_500.vidw column=value }}} plot: {{{ d.mon x0 d.resize w=666 h=1006 d.font Vera d.split.frame frames=2 # d.frame uno MAP=gauss r.colors ""$MAP"" col=bcyr d.rast ""$MAP"" d.vect gauss_rand_500 icon=basic/point fcolor=none color=60:60:60 d.legend ""$MAP"" at=5,60,2,5 echo ""$MAP"" | d.text color=black size=4 # d.frame dos MAP=gauss_rand_500.vidw r.colors ""$MAP"" col=bcyr d.rast ""$MAP"" d.vect gauss_rand_500 icon=basic/point fcolor=none color=60:60:60 d.legend ""$MAP"" at=5,60,2,5 echo ""$MAP"" | d.text color=black size=4 }}} fwiw I also notice that the module does not scale well to large region sizes (at all). thanks, Hamish",defect,closed,major,6.4.4,Vector,svn-develbranch6,fixed,v.surf.idw,,x86-64,Linux