The accuracy of Digital Elevation Models interpolated to higher resolutions

This paper presents theoretical and practical assessments of the accuracy with which Digital Elevation Models (DEMs) can be interpolated to higher resolutions and demonstrates that simple bilinear or bicubic convolution is an adequate approach. It is assumed that the DEM is defined on a square grid and is free of error. In other words, this paper does not consider the question of how irregularly distributed elevation measurements should optimally be resampled on to a square grid. The achievable accuracy depends principally on the fractal dimension of the surface and the standard deviations of the height difference between adjacent grid points in the original DEM. The accuracy depends only slightly on the factor by which the resolution of the DEM is increased, and it is typically between 0.2 sigma and 0.6 sigma. The paper briefly discusses the implications of these results for one remote sensing application: the correction of Synthetic Aperture Radar imagery for the effects of terrain-induced distortion.