[GRASS-user] r.in/out.xyz question

Frank Broniewski liste at geo-dienstleistung.de
Sat Dec 1 04:31:30 EST 2007


Am Samstag, 1. Dezember 2007 00:08:08 schrieb Hamish:
> Frank Broniewski wrote:
> > I am experimenting with r.in/out.xyz. As far as I understand, r.out.xyz
> > take a cell center coordinate and writes this and the associated z value
> > into something(stout/file).
> > Now I have recognised while importing the output with r.in.xyz that there
> > is a different cell count with different rasters while the region is the
> > same.
>
> [Glynn answered this probably comes from r.slope.aspect]
>
> > I am sorting the output by the z value in order to create classes of
> > equal area
>
> perhaps 'r.univar -e percentile=' for percentile in n*(100/num classes)
> makes this much easier?
>
>
> Hamish
>
>
>
>      
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I tried the percentile option from r.univar already, but this only works good 
for normal distributed data. I got quite nice (but not perfect) results for 
my terrain model, but really no good results for slope and other similar 
distributed data with a single very high peak.

Counting cells for equal area is more robust towards the z-value than any 
statisticial method I tried so far, although I always have trouble when it 
comes to statistics in general ;-)
I am just writing a perl script for this, so that things can be automated as 
much as possible.

r.slope.aspect seems really to blame for the null values. I just overlayed the 
slope map over the terrain map with the d.rast overlay option and there is 
indeed a 1-cell wide boundary. I would have never figured that out.
Thanks alot.

Frank


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