## 2438Re: [ai-geostats] Re: Software for Automatic Semivariogram Estimation

Expand Messages
• Feb 28, 2006

Dear Prof. Clark

Here is the paper:

http://www.ansinet.org/fulltext/jas/jas581405-1407.pdf

Formula (4) is the weight factor.

King regards.

Behrang.

----- Original Message -----
Sent: Tuesday, February 28, 2006 9:53 PM
Subject: [ai-geostats] Re: Software for Automatic Semivariogram Estimation

Behrang

What weighting do you use in the weighted least squares?

Isobel
http://www.kriging.com

Behrang Kushavand <Kushavand@...> wrote:
hi,
I have a software for Variogram AUTO Modeling (winvam) that works with gslib
(GAMV.exe).

First you must calculate experimental variogram (omni or directional) with
gamv.exe and then by using winvam, you can fit the best model by least
square and weights least square criteria for given model(s),

You can find it at:

http://www.ai-geostats.org/software/Geostats_software/WinVAM.htm

King regards.

Behrang.

----- Original Message -----
From: "Edzer J. Pebesma"
To: "Mach Nife"
Cc: "ai-geostats"
Sent: Tuesday, February 28, 2006 7:59 PM
Subject: Re: [ai-geostats] Software for Automatic Semivariogram Estimation

> Mach Nife wrote:
>
> >Hi,
> >
> >I'm hunting for a software (freeware/openSource if
> >possible), that would help estimating the best
> >possible semivariogram curve in a non-interactive way.
> >As an example, ArcGis Geostatistical Analyst does a
> >pretty good job at this when we accept the defaults.
> >It does some automatic calculations for the parameters
> >of the selected model. I've tried Gstat "Fit" method
> >(in the command-line version), but the results aren't
> >what I expected. What I need is a command line
> >software or one that can be controlled by programming.
> >
> >Any ideas?
> >
> >
>
> Some. I did have a look at your data, and at the
> ArcGIS fit window you sent me. Clearly, we do not
> fully agree on what is to be considered a "good" job.
> ArcGIS calculates semivariances up to the largest
> distances present in your data set; afaik the general
> recommendation is not to look further than half the
> longest distance (compare acf computation in time
> series); the gstat default is one third the diagonal
> of the area spanned. Have you tried modifying any
> of these defaults? Interval widths?
>
> When looking at the fit, it seems that ArcGIS shows
> a couple (4?) directional variograms in a single
> plot, but apart from that, the sample variogram suggests
> a linear model. It is obvious that fitting three parameters
> (exponential model with nugget) to something that
> tends to be linear will lead to problems -- an infinite
> set of solutions, for instance. When you insist on
> having an exponential model, you could for
> instance force the range to a certain (large) value.
> I suspect ArcGIS stops adjusting the range of the
> exponential model when it exceeds the data extent
> (Constantin, are you with us?), but should that be
> considered good practice?
>
> My experience with automatic, general-purpose
> automatic variogram fitting are not very positive;
> if it were, gstat would probably have such a function.
>
> Are there other ai-geostats readers who have positive or
> negative experiences with, or who routinely trust,
> automatically fitted variograms? Which software?
>
> Looking forward to a heated debate,
> --
> Edzer
>
> >machnife
> >
> >__________________________________________________
> >Do You Yahoo!?
> >Tired of spam? Yahoo! Mail has the best spam protection around
> >http://mail.yahoo.com
> >
> >
> >
> >------------------------------------------------------------------------
> >
> >* By using the ai-geostats mailing list you agree to follow its rules
> >( see http://www.ai-geostats.org/help_ai-geostats.htm )
> >
> >* To unsubscribe to ai-geostats, send the following in the subject or in
the body (plain text format) of an email message to sympa@...
> >
> >Signoff ai-geostats
> >
>
>
>

----------------------------------------------------------------------------
----

> * By using the ai-geostats mailing list you agree to follow its rules
> ( see http://www.ai-geostats.org/help_ai-geostats.htm )
>
> * To unsubscribe to ai-geostats, send the following in the subject or in
the body (plain text format) of an email message to sympa@...
>
> Signoff ai-geostats

* By using the ai-geostats mailing list you agree to follow its rules
( see http://www.ai-geostats.org/help_ai-geostats.htm )

* To unsubscribe to ai-geostats, send the following in the subject or in the body (plain text format) of an email message to sympa@...

Signoff ai-geostats
• Show all 13 messages in this topic