Abstract

Digital Elevation Models (DEMs) defined as digital representation of the ground surface are widely used by many disciplines for various purposes. In parallel with technological developments, DEMs are generated from different sources such as direct surveys, digitization of digital contour maps, aerial photographs, remote sensing images, laser scanning systems, interferometric SAR data etc. Many researches have been conducted on the factors affecting the accuracy of the DEMs and they are still ongoing. In this study, effect of land slope on the accuracy of DEM has been researched. Therefore, land cross-sections have been determined in the diverse land slope groups on the area of study. Land surveys have been made on these cross-sections by electronic tachometer. Three dimensional coordinates (x, y, z) of the points surveyed on the cross-sections have been calculated. Later, maps with 1/5000 scale 5 m contour intervals and 1/25000 scale from 10 m contour intervals were digitized. DEM was derived from digital orthophoto map with 1/1000 scale. Also, DEMs of the area of the investigation were generated using IKONOS satellite image with 1 m resolution and SRTM (Shutle Radar Topography Mission) data. Differences were acquired by determining elevations on the DEMs generated using five different maps and images pertaining to the same point, based on the points of which surveys and elevations were determined. Elevation accuracy of the DEMs derived from different sources was assessed for each cross-section by means of the differences acquired and comparisons were carried out.

Key words: Digital elevation model, counter maps, digital orthophoto, SRTM data.