[R-sig-Geo] intamap: mixed anisotropy

[seba]

Dear Edzer and Giannis

Thank you for your reply. I think that I should 
subscibe to intamap-info list considering
that I'm using extensively some of the intamap 
functions....and sooner or later I think
to use them in my geostatistics courses.

Ok, so you confirm that is limited to geometric 
anistropy. Now I'll try to check
what the routine do in presence of mixed 
anisotropy; as I mentioned earlier I have the fealing (coming
from using it with very heterogenous, from the 
spatial variability point of view, data sets) that
the anisotropy ratio coming out is meaningfull 
also in case of zonal/mixed anisotropy (at least for my task
that is for spatial variability carachterization 
and not for conducting interpolation with kriging). I'm going
to check it.
Thank you again for your help

Sebastiano

At 10.40   20/04/10, Edzer Pebesma wrote:
>Dear Seba, Giannis Spilliopoulos, the author of estimateAnisotropy, sent
>me the answer below when I forwarded your email to the intamap-info list
>on sourceforge.
>
>Dear Sebastiano and Edzer
>
>Thank for using Intamap package. The "estimateAnisotropy" function is
>developed to detect only geometric anisotropy. It is not tested in case
>of zonal anisotropy, as  we consider it future work.
>
>As for the anisotropy estimates, given a Cartesian coordinate system
>(X,Y) we examine two cases:
>
>a)In the case of zero direction and ratio R (0,R). One should interpret
>this result as the correlation length along X axis  is R times bigger
>the correlation length along Y axis.
>
>b)In case of  theta degrees and ratio R (theta,R). You should think that
>the major correlation length
>needs a theta degrees (clockwise) rotation to align with the horizontal
>axis. In case of negative angle the rotation should be performed
>counter-clockwise. Ratio R in this case yields that the correlation
>length on theta degrees is R times bigger than the correlation length in
>theta+90 degrees.
>
>To sum up the direction represents the angle between the direction of
>the major correlation length and the horizontal axis. While the ratio
>represents the ratio of the major to minor correlation lengths.
>
>I hope this helps.
>
>Sincerely
>Giannis
>
>
>seba wrote:
> >
> >> Date: Tue, 20 Apr 2010 12:24:34 +0200
> >> To: r-sig-geo at stat.math.ethz.ch
> >> From: "S. Trevisani" <s.trevisani at irpi.cnr.it>
> >> Subject: Intamap: mixed anisotropy
> >>
> >> Dear list members
> >>
> >> I'm using some of the functions of the intamap packages.
> >> I like very much the estimate anisotropy function, it is really useful
> >> for my tasks.
> >> But I'm wondering how to deal with zonal or mixed anisotropy
> >> considering that
> >> the function is designed for detecting geometric anisotropy (anyway, I
> >> saw that also in the case of geometric anisotropy, the function tells
> >> me correctly the direction of maximum variability, but I'm not sure
> >> how to interpret the ratio).
> >>
> >> Thank you for your feedback!
> >>
> >> Sincerely
> >> Sebastiano
> >
> > _______________________________________________
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> > R-sig-Geo at stat.math.ethz.ch
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>
>--
>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