Özet:

Digital Elevation Models (DEM) are widely used in many different applications such as orthophoto production, 3D city models, hydrological modeling, visibility, flood, flood analysis and etc. The densest grid spacing DEM covering Turkey is the DTED-2 data produced by the General Command of Mapping with a grid spacing of 1 second (approximately 30 m). Denser and more accurate DEM is produced by several institutions in only required areas but not covering whole country. Governmental institutions need denser, more accurate, homogeneous and countrywide DEM. This study is conducted to meet DEM demands with optimum accuracy and density by stereo aerial photos. In order to investigate the optimal resolution for a countrywide DEM, test DEMs are produced in three different areas representing the general topographic structure of Turkey by using 45 cm ground sampling distance stereo aerial photos. The Root Mean Square Error (RMSE) of the heights of three areas are respectively ± 2.51 m, ± 1.38 m and ± 1.30 m. The proposed grid spacing by INSPIRE with these accuracies is 3-30 m in flat terrain and 3-15 m in mountainous terrain. It is concluded that 5 m grid spacing will be suitable for a countrywide DEM with the above mentioned accuracies. It is also proposed that production format of DEM should be 32 Bit Floating GeoTiff.

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