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GEOSTATS: Variowin - GSTAT conversion??

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• Greetings, I am a newcomer to this list, indeed to geostatistics, but I couldn t find this question in the FAQ. My colleagues and I have several hundred dates
Message 1 of 1 , May 27, 1999
Greetings,
I am a newcomer to this list, indeed to geostatistics, but I couldn't
find this question in the FAQ. My colleagues and I have several hundred
dates of both potential evapotranspiration and precipitation data as
well as soil profiles that we are attempting to krige. We purchased
several intro-to-geostatistics-texts, the VARIOWIN book/software, and
have created variogram models for each of our datasets. We plan to krige
our data using GSTAT 2.0. However, we're having a couple difficulties
with the conversion. The following is a sample variowin model
(jun97pet.mod):

The variogram model (for the same data) in VARIOWIN looks like the
following:
MODEL PARAMETERS
Measure of spatial continuity: Variogram
Variable(s): PET
EXPERIMENTAL VARIOGRAMS
Direction: 50 - Tolerance: 30 - MaxBW.: N/A
Direction: 0 - Tolerance: 30 - MaxBW.: N/A
Gamma(h): 1.058 + 3.404 Gauss.18 (h)
Dir.(1): 50 | anis.(1): 1000
IGF: 5.3989e-02
A priori covariance: 4.5763e+00 A priori correlation: 1e+00
MODEL PARAMETERS TO BE INCLUDED IN A GSLIB PARAMETER FILE
1 1.058 :nst, nugget
3 10.392304 3.404 40 1000 :it, aa, cc, ang1, anis

When I translate this model to use in a GSTAT command file, I have used
the following (contents of jun97pet.cmd):

data(jun97pet):'jun97pet.eas', x=1, y=2, v=3;
mask: 'samask';
variogram(jun97pet): 1.058 Nug (0) + 3.404 Gau (18,40,1000);
predictions(jun97pet): 'jun97_pr';
output: 'jun97prd.eas';

When the above command file is run in GSTAT, it crashes with the
following report to the screen:

C:\GSTAT>gstat jun97pet.cmd
gstat 2.0i (February 1999) for Win32
Copyright (C) 1992, 1999 Edzer J. Pebesma
parsing anis(40,0,0,1000,1), error on 1000
gstat: variable outside valid range: this value should be in <0..1]

Is this because GSTAT is expecting an anisotropy correction as a ratio
between 0..1 and we
are supplying something else? How do we calculate the correct value from
our model (above)?

Also, we think that there are directional issues between the two
softwares VARIOWIN and GSTAT. We understand that Zero degrees in
Variowin is 90 degrees in GSTAT, 5 degrees in Variowin is 85 in GSTAT,
and so on. Are we correct in our assumption?

Is there anything missing from our GSTAT command file that we can
correctly gain from our VARIOWIN model to aid in our kriging, and ought
to use? Thanks in advance for any help you can offer.

Regards,

Peter Schlesinger

--
Peter Schlesinger
GIS & Remote Sensing Laboratory
Woods Hole Research Center
PO Box 296, 13 Church Street
Woods Hole, MA 02543
(508)540-9900, ext 118
(508)540-9700, fax
email: pschles@...
WWW: www.whrc.org

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