On Tue, 13 Apr 2010, Jachym Cepicky wrote:
Hi,
I can not get reasonable result (compared with v.surf.rst) from
v.surf.idw using attached input vector points
is it possible, that v.surf.idw is kind of broken?
Hello,
I can confirm that I can reproduce the strangeness, that it only happens
when *not* using the -n flag (i.e. when indexing points) and that it
happens when interpolating a relatively small number of points into a
region with a relatively high resolution. E.g. for the given data I
observe strangeness for a resolution of 10, but it goes away either by
specifying the -n flag or decreasing the resolution to 15.
It does indeed look to be caused by my buggy code from 2003, or (perhaps
less likely; I'm not sure) some later change to it - specifcally something
to do with the "shortlist" method of avoiding an intensive search for
nearby sites/points when the number of points is relatively small compared
to the region size.
I can't see anything obviously wrong but I'll look into it over the next
few days...
Paul
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