In the current investigation, a 5'x5' digital terrain model for Egypt was computed by collocation, based on the available local height data and the high-resolution harmonic model GTM3a. Exploiting the dominant moderately varying Egyptian territory, the global high frequency topographic harmonic model was removed prior to the prediction into a grid and a posteriori restored at the grid nodes. A removal and restoration of a suitable trend surface, based on the residual height data, has also contributed to the smoothing strategy. According to the limited coverage and resolution of the available height data, the global-wise accuracy of the resulting DEM was found to be ± 29 meters. |
