[R-sig-Geo] anisotropy modeling

[Matevž Pavlič]

Hi, 

thanks for the reply. Can you explain this a little bit more :
" it assumes the variogram to fit to is in the major (correlation) direction (or averaged over all directions)."

I don't know exactly ehat it means....
m

-----Original Message-----
From: r-sig-geo-bounces at r-project.org [mailto:r-sig-geo-bounces at r-project.org] On Behalf Of Edzer Pebesma
Sent: Wednesday, July 13, 2011 10:10 AM
To: r-sig-geo at r-project.org
Subject: Re: [R-sig-Geo] anisotropy modeling



On 07/12/2011 10:52 PM, Matevž Pavlič wrote:
> Hi all,
> 
>  
> 
> i 'm am not entirely sure I understand anisotropy kriging in R. 
> 
> I have a data set in which is (at least i think so) anisotropy is clearly visible. So I made directional variograms....
> 
> So as i understand, the only thing that is different from >normal< kriging is the  >anis< property in which you define the diffrenece of ranges? Is that coreect?

Yes. Please note that fit.variogram ignores anything about anisotropy, it assumes the variogram to fit to is in the major (correlation) direction (or averaged over all directions).

> 
> Bellow is the code i use :
> 
>  
> 
> a<-5000/7000
> 
> print(plot(variogram(Z ~ 1, DF, map = TRUE, cutoff = 15000, width = 
> 100), main = "Variogram map, podlaga",col.regions = 
> terrain.colors(64)))
> 
> v1.a<-variogram(Z~1, DF, alpha=c(45, 135))
> 
> (vmf.a <- fit.variogram(v1.a, vgm(2900, "Pen", 5500, 300, anis = 
> c(135, a))))
> 
> print(plot(v1.a, pl = F, pch = 20, col = "blue"))
> 
> print(plot(v1.a, plot.numbers = F, pch = 20, col = "darkblue", model = 
> vmf.a))
> 
>  
> 
> podlaga.aniso<-krige(Z~1, DF[-zerodist(DF)[,1],], grd, vmf.a )
> 
> print(spplot(podlaga.aniso, zcol="var1.pred", 
> col.regions=terrain.colors(64), contour=T, pretty=T, cuts=15, 
> key.space="right"))
> 
> print(spplot(podlaga.aniso,  zcol="var1.var", 
> col.regions=terrain.colors(64), contour=T, pretty=T, cuts=15, 
> key.space="right"))
> 
> writeGDAL(podlaga.aniso, "podlaga_aniso.tif")
> 
>  
> 
> thanks for info,
> 
>  
> 
> m
> 
> 
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> 
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--
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251 8333081, Fax: +49 251 8339763  http://ifgi.uni-muenster.de
http://www.52north.org/geostatistics      e.pebesma at wwu.de

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