An Evaluation of Digital Elevation Models for
Upgrading New Zealand Land Resource
Inventory Slope Data
Landcare Research NZ Ltd.
P.O. Box 69, Lincoln 8152
New Zealand
Presented at the second annual conference of GeoComputation ‘97 & SIRC ‘97, University of Otago, New Zealand, 26-29 August 1997
Abstract
Slope is a key environmental parameter which influences land use and erosion hazard. Digital elevation models (DEMs) are often used to map important topographic parameters such as slope. However, the quality of such maps depends on the quality of the DEM’s representation of the earth’s surface. In many cases errors in this representation are neither measured nor estimated. In this paper a real-time differential GPS is used to acquire ground truth data. This ground truth is compared with DEMs generated from contours. This analysis shows that three commonly used contour-based interpolation procedures all produce good quality DEMs.When considering the replacement of more traditional slope maps based on field mapping or air photo and contour interpretation with DEM-derived slope maps, it is important to establish that DEM-derived slope maps do represent an improvement on existing approaches. This paper compares field mapped and DEM-derived slope maps with slopes calculated from GPS elevation data. It shows that DEMs can provide both improved spatial resolution and increased accuracy in slope maps.