Dear everybody!!

I´m working with bathimetric data of a shallow lake.
Performing the spatial analysis with R-gstat I found strong anisotropy, to
say, zonal anisotropy, because both, range and sills are different.

I have read a bunch of stuff including gstat manual e.g.(
http://www.gstat.org/manual/node20.html) as well as some material from this
list (http://www.gstat.org/gstat-info/msg00171.html).

My directional variograms indicate two directions, the major spatial
dependency is 55º and the minor is 145º. Ranges are 3000 for 55º and 1200
for 145º. While sills are about 5.8 for the 55º and 8.1 for the 145º. Then
the parameters of the model acording to the manual (c Mod(a, p, s)) are:

a=3000
p=55º
s=0.4

The earlier mentioned post in the list mentions that gsat does not fit
automatically anisotropic variograms.

¿Is it there another R geostatistical package or standalone software that
does?

In the mentioned list post E.Pebesma explains about transforming the
coordinates to generate isotropic coordinates and then fit the variograms.
I understood that this could be done by rotating the coordinates axis to
align them to the main and secondary anisotropy axis, and maybe then
multiplying the new X coordinate value by S.

¿How do I do that if I already have a SpatialPointsDataFrame in R?

In the same post is mentioned that the anisotropic sills are not the more
important part when performing kriging interpolation and that a solution
would be to average the directional sills. I understood this because the
rising part of the variogram and how this raise is modeled is critical to
kriging interpolation, while the sill would be less important because it
accounts for the spatial dependency where THERE is no more spatial
dependency.

¿Am I getting this right?.

Thanks to every body, Cheers!!

-- 
Dr. Alberto Gómez-Tagle (Jr)
Associate Researcher
Soil Laboratory
Earth Sciences Department
INIRENA-UMSNH

Av. Sn. Juanito Itzícuaro SN
58330
Morelia, Michoacán
México.

Tel: +52 (443) 3.27.23.50 (ext.109)
Fax: +52 (443) 3.27.23.51

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