[GRASS-user] Re: strange behaviour of v.surf.idw

[G. Allegri]

I used -n flag. The surface is now more realistics and appears allineated to
the narrower IDWs results:
http://www.geospatial.it/allegri/IDW5.png<http://www.geospatial.it/allegri/IDW4.png>.
I can't access your PhD thesis...

Giovanni

2008/2/13, Luigi Ponti <lponti at infinito.it>:
>
> Dear Paul,
>
> I have found your PhD thesis excerpt very interesting: thanks for
> sharing it.
> > Date: Tue, 12 Feb 2008 21:31:44 +0000 (GMT)
> > From: Paul Kelly <paul-grass at stjohnspoint.co.uk>
> > Subject: Re: [GRASS-user] strange behaviour of v.surf.idw
> > To: "G. Allegri" <giohappy at gmail.com>
> > Cc: grassuser <grass-user at lists.osgeo.org>
> >
> > Also, have you tried running using the -n flag (no indexing) and
> comparing
> > the results. I think they should be the same for all regions then but
> > might turn up something else interesting.
> >
> I started using v.surf.idw (for irregularly spaced points) in grass6.0
> with no -n flag, then in 6.1 I noticed that the output raster changed
> from what it used to be (i.e., some stair-like artifacts appeared) and
> it was restored to the original look (i.e., a much smoother look) by
> adding the -n flag. By looking at your PhD thesis excerpt, it looks like
> the -n flag should only make the interpolation faster: I wonder if you
> have any idea why there may be differences, as you also say above.
>
> Kind regards,
>
> Luigi
>
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