Surface Analysis

Interpolation

• Interpolate a surface from point data using either a weighted-distance or potential surface model.
• Interpolate a surface from a set of contours by linear interpolation.
• Produce Thiessen polygons (a Voronoi Tessellation) about a set of irregularly distributed points.
• Calculate the best fit using up to a 9th order trend surface to a set of irregular cell control points by least-squares procedures.

TIN Interpolation

• Generate a Triangulated Irregular Network (TIN) model from either isoline vertices or vector point input data using either a constrained or non-constrained Delaunay triangulation. Includes an optimization routine to remove bridge and tunnel edges.
• Generate a raster surface image from an existing TIN model.

Geostatistics

• Spatial Dependence Modeler - modeling tools for spatial variability or spatial continuity using semivariogram, robust semivariogram, covariogram and correlogram, cross variogram, cross covariogram, and cross correlogram methods. Directional and surface variograms, h-scatterplots, indicator transform, and thresholding supported.
• Mathematical fitting of model variogram to sample variogram using spherical, exponential, Gaussian, linear, linear-with-sill, power, logarithmic, circular, pentaspherical, Bessel and periodic curves. Modeling geometric and zonal anisotropy supported.
• Surface interpolation using simple and ordinary kriging, simple and ordinary cokriging, and Gaussian simulation. Kriging options include cross-validation, block averaging, and stratified kriging. Statistical options for distance to simulation, nearest/farthest observation for each pixel, number of observations in neighborhood, and local quantile or median estimation are also supported. Local neighborhood and sample selection supported by a variety of methods.

Topographic Variables

• Produce a slope gradient image from a surface model.
• Produce an aspect image from a surface model.
• Produce an analytical hillshading image from a surface model.
• Calculate the maximum rate of change along the slope of a pixel in the aspect and orthogonal directions.
• Calculate the fractal dimension of a surface.

Feature Extraction

• Generate contours from any raster surface image at user-defined intervals.
• Classify a surface into eleven different features including: peak, ridge, saddle, flat, ravine, pit, convex hillside, saddle hillside, slope hillside, concave hillside, and inflection hillside.
• Remove local depressions from a surface image.
• Calculate convergent flow accumulation using a modified aspect algorithm.
• Calculate flow direction.
• Revised Universal Soil Loss Equation (RUSLE) model for modeling erosion potential.
• Determine the boundaries of watersheds and subwatersheds given a minimum subwatershed size or a seed image.
• Calculate slope length and determine image homogeneity.