Comparison of DEM Data Capture and Topographic Wetness Indices

Digital elevation models (DEMs) can be captured and analysed by various methods. Elevation capturing with RTK-GPS and airborne laser scanning is presented and evaluated in terms of height accuracy of raw data and interpolated DEMs for study sites in Sweden and Germany. Applications for precision agriculture are based on the connection of land surface and the movement of water in the landscape. Three methods of deriving potential flow accumulation from DEMs are discussed. Results indicate that the Topographic Wetness Index can be used to assess the pattern of potential soil moisture on a field and changes in soil texture caused by erosion processes. The quality of the soil moisture assessment varies with both flow algorithm and terrain characteristics. Correlations up to r2 = 0.64 were found. Best results were obtained on undulating farmland using the DEMON algorithm and a formbased approach. However, in areas with low relief, the concept did not lead to valuable soil moisture maps.