Gstat is a program for the modelling, prediction and simulation of geostatistical data in one, two or three dimensions. Geostatistical data are data (measurements) collected at known locations in space, from a function (process) that has a value at every location in a certain (1, 2 or 3-D) domain. These data (or some transform of ... them) are modelled as the sum of a constant or varying trend and a spatially correlated residual. Given a model for the trend, and under some stationarity assumptions, geostatistical modelling involves the estimation of the spatial correlation. Geostatistical prediction (`kriging') is finding the best linear unbiased prediction (the expected value) with its prediction error for a variable at a location, given observations and a model for their spatial variation. Simulation of a spatial variable is the creation of randomly drawn realizations of a field given a model for the data, possibly conditioned on observations.
In gstat, geostatistical modelling comprises calculation of sample variograms and cross variograms (or covariograms) and fitting models to them. Sample (co-) variograms are calculated from ordinary, weighted or generalised least squares residuals. Nested models are fitted to sample (co-) variograms using weighted least squares, and during a fit each single parameter can be fixed. Restricted maximum likelihood estimation of partial sills is also implemented. In the interactive variogram modelling user interface of gstat, variograms are plotted using the plotting program gnuplot.
Gstat provides prediction and estimation using a model that is the sum of a trend modelled as a linear function of polynomials of the coordinates or of user-defined base functions, and an independent or dependent, geostatistically modelled residual. This allows simple, ordinary and universal kriging, simple, ordinary and universal cokriging, standardised cokriging, kriging with external drift, block kriging and ``kriging the trend'', as well as uncorrelated, ordinary or weighted least squares regression prediction. Simulation in gstat comprises uni- or multivariable conditional or unconditional multi-Gaussian sequential simulation of point values or block averages, or (multi-) indicator sequential simulation.
Besides many of the common options found in other geostatistical software packages, gstat offers the unique combination of:
- an interactive user interface for modelling variograms and generalised covariances (residual variograms), that uses the device-independent plotting program gnuplot for graphical display - support for several ascii and binary data and grid map file formats for input and output - a concise, intuitive and flexible command language - user customization of program defaults - no built-in limits - free, portable ansi-c source code
Fitting power variogram models does not work variograms are written twice from user interface ('c') progress reports (xx % done) may overflow for large data sets warning message: `ALL data outside map' may occur unjustified.
Access Constraints
Gstat is Open Source software, distributed under the terms of the GNU General Public Licence (meaning it's freely available in binary and source code form).
Use Constraints
Gstat is free software; you can redistribute it and/or modify it under the terms of the GNU General Public Licenceas published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. Gstat is distributed in the hope that it will be useful, but without any warranty; without even ... the implied warranty of merchantability or fitness for a particular purpose. See the GNU General Public License for more details. You should have received a copy of the GNU General Public Licencealong with the program (see the file COPYING); if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Gstat works at least on the following platforms: Linux, hp-ux (9.x, 10.x), aix (3.2, 4.1), OSF/Alpha, SunOS, SGI, win32 and MS-DOS (dpmi).
TYLER
B.
STEVENS Role:
SERF AUTHOR
Phone:
(301) 614-6898
Fax:
301-614-5268
Email:
Tyler.B.Stevens at nasa.gov
Contact Address:
NASA Goddard Space Flight Center
Global Change Master Directory City:
Greenbelt
Province or State:
MD
Postal Code:
20771
Country:
USA
Publications/References
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
Corrections have made to the proofs of this article but the corrections have not made it into the final version. The most important ones are listed below:
- the file names in the gstat ... commands appear between ` and ' but should have appeared between ' and ' (or, alternatively, between " and " ). Also, gstat will interpret white space between quotes as part of a file name. Thus: everywhere the file name ` zinc.eas' should have read 'zinc.eas'
* Page 18, Column 1, line 8 from below: V = [Cov(e(si),e(sj))]nxn * Page 19, Column 2, line 14: there should be a hat on eols * Page 20, Column 1, lines 4-9: matrices should be non-bold * Page 22, Column 2, line 8 from below: x=2&x&y should have been X=2&x&y * Page 23, Column 1, line 13 from below: predictions(zinc): 'zinc_id.pr'; * Page 23, Column 2, line 3: variance should have been partial sill
Additional references (bibliography) can be found at the following URL:
Creation and Review Dates
SERF Creation Date: SERF Last Revision Date:
2011-01-26
Links
