National Center for Geographic Information and Analysis

The first paper describes the implementation of three methods for fitting surfaces: linear, quintic and stochastic. It uses qualitative (visual) and quantitative (statistical) criteria to compare the three approaches. The digital terrain model is based on a triangular irregular network (TIN) structure and the comparison is performed using a mathematically defined function and real data obtained from a raster digital elevation model (DEM) from a United States Geological Survey (USGS) elevation file.

The second paper addresses the problem of constructing Triangular Irregular Network (TIN) models from irregularly distributed samples with constrained lines. The implementation of an incremental constrained Delaunay triangulation is described and compared qualitatively with the unconstrained Delaunay triangulation.