Assessment of interpolation methods for refining SRTM and DEM

Shuttle Radar Topographic Mission (SRTM) DEM is widely used in analyzing topography of developing countries because it is freely available. But due to its coarse resolution (3 arc-second or 90m), the SRTM is sometimes not appropriate for use in hydrologic analysis and deriving stream networks. The purpose of this study was to evaluate the potential and performance of seven interpolation techniques as a means of refining the resolution to 30m. IDW with exponents of 0.5, 1, and 2, regularized and tension Spline, Kriging, and Natural Neighbor interpolation were tested using ArcGIS 9.1 Spatial Analyst. The obtained elevation, slope, aspect, sink, and stream networks from the interpolated 30m DEM were compared quantitatively with those derived from the original 30m SRTM DEM. The Renasco River area of New Mexico was selected for the analysis area because it has a range of topographic features from flat lands and hills, to mountains.