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What is it?
Gstat is an open source (GPL) computer code for multivariable geostatistical modelling, prediction and simulation, and has been around from 1997. In the original form, gstat is a stand-alone executable, interfaced to various GIS. As of 2003, the gstat functionaly is also available as an S extension, either as R package or S-Plus library. Current development mainly focuses on the S extension. The reason for this is obvious for those familiar with R and/or S-Plus.Functionality
Gstat can calculate sample variograms, fit valid models, show variograms, calculate (pseudo) cross variograms, fit valid linear models of coregionalization (S extension only), and calculate and fit directional variograms and variogram models (anisotropy coefficients are not fitted automatically).Kriging and (sequential) conditional simulation are done under (simplifications of) the universal cokriging model. Any number of variables may be spatially cross-correlated. Each variable may have its own number of trend functions specified (being coordinates, or so-called external drift variables). Simplifications of this model include ordinary and simple kriging, ordinary or simple cokriging, universal kriging, external drift kriging, Gaussian conditional or unconditional simulation or cosimulation. In addition, variables may share trend coefficients (e.g. for collocated cokriging).
References
Two gstat references in Computers and Geosciences:- Edzer J. Pebesma and Cees G. Wesseling, 1998, Gstat: a program for geostatistical modelling, prediction and simulation. Computers & Geosciences Vol. 24, No. 1, pp. 17-31 (a paper full with typos).
- Pebesma, E.J., 2004. Multivariable geostatistics in S: the gstat package. Computers & Geosciences, 30: 683-691.
Graphics
Gstat was designed to do calcutions, not graphics. Other programs or environments are better for this. For many years, gstat (stand-alone) used gnuplot for the display of sample variograms and variogram functions. Gnuplot is a program for plotting functions and data, ported to most computer platforms, and allows saving graphs in many formats (EPS, PNG, gif, cgm, LaTeX, fig, etc.).With the gstat S extension, the full suite of graphics capabilities of S becomes available, and the following is currently used by gstat:
- conditioning plot to show multivariable variograms
- conditioning plot to show directional variograms
- identifying point pairs on a variogram cloud, combined with a visualisation of the point pair in a map view
- selecting a set of points by digitizing an area, combined with a visualisation of the point pair in a map view
About gstat.org
The domain www.gstat.org is hosted by the Department of Geography at Utrecht University, the Netherlands.Last modified: February 15, 2006 Page contents by Edzer J. Pebesma, page layout by Kor de Jong. Send comments.