Report: Comparison of Methods to Produce Digital Terrain Models

This report compares Digital Terrain Models (DTM) created through two separate processes from the same source data. Using mass point and breakline data provide by a private contractor as part of the State Addressing and Mapping Board (SAMB) project, we created two versions of a DTM for the Lorado 7 1⁄2’ Quadrangle in southern West Virginia. We first employed the traditional method of transforming mass points and breaklines into gridded elevation data. That method involves creating Triangular Irregular Networks or TINs. The TINs are transformed into lattices and eventually into digital terrain models in USGS DEM format. The final product has a 3 meter pixel size with horizontal units of meters and vertical units of feet. We will not discuss the methodology for creating these products in this report. As a comparison test, we utilized the TOPOGRID command in Arc Info to generate a surface. TOPOGRID is an interpolation method designed to harness the efficient computing characteristics of local interpolators such as inverse distance weighting, while conserving the power of global interpolators like kriging. TOPOGRID is designed to minimize generalization of abrupt features such as streams and ridges. It is based on the ANUDEM program developed by Michael Hutchinson (ESRI 2001). This report is essentially a comparison of a vector surface elevation model (TIN) and a raster surface elevation model. It is true that we are comparing two rasters, but one of these surfaces was derived from a TIN, which is a vector data format. Both of these formats have their advantages and disadvantages, both of which will be discussed here (Zeiler 1999).