By Interferometric Synthectic Aperture Radar (InSAR), during the Shuttle Radar Topography Mission (SRTM) height models have been generated, covering the earth surface from 56 degrees south to 60.25 degrees north. With the exception of small gaps in steep parts, dry sand deserts and water surfaces, the free available US C-band data cover the earth surface from 56 south to 60.25 degrees north completely while the X-band data, distributed by the DLR (German Aerospace Center), cover it only partially. The C-band and X-band radar cannot penetrate the vegetation because of the short wavelength. Therefore, the height models are not Digital Elevation Models (DEM) representing bare Earth surface without any details, they are Digital Surface Models (DSM) representing the visible surface including vegetation and buildings. In the area of Zonguldak, Turkey, C-band and X-band DSMs are available and have been analysed in cooperation between Zonguldak Karaelmas University (ZKU) and Leibniz University of Hannover. The digitized contour lines from the 1:25,000 scale topographic maps and also a more precise height model derived directly from large scale photogrammetric mapping are used as reference height models.