Comparison of Digital Elevation Data from Airborne Laser and Interferometric Sar Systems

Requirements for precise digital elevation data (i.e., Digital Elevation Models, or DEMs) of varying levels of detail are being formulated for different fields of application. The degree of detail found in a DEM is usually characterized by the horizontal sample spacing and by the vertical accuracy of the samples. Increased detail is normally associated with increased cost to the user, which fuels the debate over which technologies are suitable for which applications. In this paper, we present the results of comparative tests of two technologies from which are derived relatively detailed digital elevation data sets with sample spacings of a few meters. The two elevation data sets have been compared for a section of variable terrain in southern Germany, approx. 10 km by 20 km in size. The data sets were produced by an airborne laser scanner and an airborne interferometric SAR sensor, respectively. The laser scanner data set consisted of two coordinated list sets of elevation measurements with a variable ground spacing ranging from approx. 1 m to 10 m. One list set contained measurement points of the earth’s surface, whereas the second list set held measurement points of the vegetation surface. The interferometric SAR data set consisted of elevation data in a regular grid with a sample spacing of 5 m. Using somewhat different approaches, the laser and radar data sets were assessed independently at the University of Karlsruhe and at Intermap Technologies, Corp. in Calgary, Canada. Three different comparative methods were applied to evaluate the elevation data sets. All comparisons came to similar results, namely, that both elevation data sets are in good agreement for bare soil or areas of low vegetation coverage (less than 0.5 m elevation difference), whereas larger elevation differences were found for all areas of substantial vegetation coverage as well as for settlement areas.