On Thu, 2004-07-08 at 08:36, Shazly, Salah DSC92 wrote: > Dear All, > > Are there any rules help building stable variograms, like number of lags, > range ..etc? And what is the minimum number of control points needed to > build a variogram? > > I am working on a subsurface oil field reservoir. > > Regards, >
Hi, Building a "stable" variogram is like magic ! You have to be a sorcerer, a good one, to deal with everything that matters and make it through the "evil forest of variogram modelling". In this list there are some of the best sorcerers you can get, so they may give you a good answer. There's a very good reference, in my opinion, about geostatistics that gives you a lot of information on the insights of variogram modelling. Applied Geostatistics () Edward H. Isaaks, R.Mohan Srivastava It's a "must have" if you want to understand geostatistics and don't want to deal with all the mathematics. If you do that then check, p.e. Statistics for Spatial Data (1993) N. Cressie You may try to model covariance without using the variogram, with MLE methods. Take a look at geoR, a package for R. http://www.est.ufpr.br/geoR/ There's also a paper about using MLS methods directly from the variogram cloud, check Muller, W.G. (1999), Least-squares fitting from the variogram cloud , Statistics & Probability Letters, 43, 93-98. Best regards EJ -- Ernesto Jardim <[EMAIL PROTECTED]> Biólogo Marinho/Marine Biologist IPIMAR - Instituto Nacional de Investigação Agrária e das Pescas IPIMAR - National Research Institute for Agriculture and Fisheries Av. Brasilia, 1400-006 Lisboa, Portugal Tel: +351 213 027 000 Fax: +351 213 015 948 http://ernesto.freezope.org
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