VARIOG2D: a computer program for estimating the semi-variogram and its uncertainty

VARIOG2D is a Fortran-77 program that provides four basic operations for se mi-variogram analysis. inference of the experimental semi-variogram, estima tion of the variance-covariance matrix of the experimental semi-variogram, fitting a theoretical model by non-linear generalised least squares and est imation of the uncertainty of the semi-variogram model parameters. Although software for estimating the semi-variogram by the method of moments is wid ely available, there is no generally available software for assessing the u ncertainty of the experimental semi-variogram. VARIOG2D provides the exact variance-covariance matrix of the experimental semi-variogram, which can be used for attaching standard errors to the experimental semi-variogram, for assessing the correlation between the different semi-variogram lag estimat es and for fitting a model by generalised least squares. In addition, the g eneralised least-squares fitting procedure allows an evaluation of the unce rtainty of the experimental semi-variogram and of the semi-variogram model parameters. A case study shows the application of the variance-covariance m atrix of the experimental semi-variogram and the performance and capabiliti es of the program. (C) 2001 Published by Elsevier Science Ltd.