Introduction

Overview

VARIOWIN 2.2 is a collection of four Windows™ programs — Prevar2D, Vario2D with PCF, Model, and Grid Display — that are used for spatial data analysis and variogram modeling of irregularly spaced data in two dimensions.

Prevar2D builds a pair comparison file (PCF), that is, a binary file containing pairs of data sorted in terms of increasing distance. Pair comparison files can be built from subsets in order to reduce memory requirements.

Vario2D with PCF is used for spatial data analysis of 2D data. It uses an ASCII data file and a binary pair comparison file produced by Prevar2D. Features implemented in Vario2D with PCF include:

• The possibility to characterize the spatial continuity of one variable or the joined spatial continuity of two variables,

• Variogram surfaces for identifying directions of anisotropies,

• Directional variograms calculated along any direction,

• Several measures of spatial continuity. Not only the variogram but also the standardized variogram, the covariance, the correlogram, and the madogram are used to measure spatial continuity.

• H-scatterplots to assess the meaning of these measures,

• The identification and localization of pairs of data adversely affecting the measure of spatial continuity. Once identified, these pairs can be masked from the calculation interactively.

• Variogram clouds for identifying pairs of data values having the most influence on the measure of spatial continuity. Those pairs can also be located on the sample map.

• The ability to save directional variograms in an ASCII file that can be used for subsequent modeling by the Model program.

The Model program is used to produce a 2D nested model of spatial continuity in an interactive way. Several directional variograms read from a variogram file produced by Vario2D with PCF are adjusted simultaneously by a 2D nested model. The adjustment is done with scroll bars. Each time a parameter of the 2D model is changed, cross sections through the 2D model are recalculated and redrawn on the experimental variograms used for the fitting procedure. The 2D nested model can be saved in a model file that is used to store the various parameters required for geostatistical estimation — kriging — or simulation.

Grid Display is used for producing pixel maps of experimental and modeled variogram surfaces that have previously been saved into grid files.