Topography plays an important role in the distribution and flux of water and energy within natural landscapes. Increasing quality and resolution of elevation information, new processing methodologies, and expanding GIS capabilities and linkages with water resources models are expected to lead to a heavier reliance on elevation data as a source of topographic and surface drainage information.
The capabilities and limitations of elevation data for use in watershed management applications include, but are not limited to: elevation data availability; elevation data vertical and horizontal accuracy; quality of the available elevation models to provide topographic and drainage information; requirement of the scale of the modeling of catchment basins; and ability to assess risk associated with flooding. The characterization of elevation data quality and the association between topography and water resources models is related to the grid sample distance (or resolution) and the vertical accuracy of the elevation data used. Moreover, the quality of readily available elevation data, varies from source to source in terms of horizontal resolution and vertical accuracy which are the two important aspects of elevation uncertainty in the modeling with raster GIS. Often times, however, the choice of elevation data (sample elevation data are illustrated below) selected will depend on budget, ability to process and analyze data, the capability to generate the necessary answers needed for a project and the mapping scale of a project (e.g. mapping scales may correspond to 1:5,000 (small village, NEXTMap 5m), 1:10,000 (town; NEXTMap 5m), 1:20,000 (large county ASTER or World 30m), and 1:50,000 (a nation; World 30m or SRTM 90m)). A few examples of elevation GSD and vertical accuracies are presented here. (more…)