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

[Luigi Ponti]

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