Department of Water and Water Structures Engineering, Faculty of Engineering, Zagazig University, Zagazig 44519, Egypt.
Civil Engineering Department, College of Engineering, Shaqra University, Duwadimi 11911, Saudi Arabia.
Int J Environ Res Public Health. 2019 Nov 1;16(21):4245. doi: 10.3390/ijerph16214245.
A digital elevation model (DEM) is a digital model or 3D representation of a terrain's surface. There are many methods to create DEM such as LiDAR, stereo photogrammetry and topographic maps. DEMs are very important for many applications such as extracting terrain parameters for geomorphology and modeling water flow for hydrology or mass movement. A number of websites are available to provide DEM such as SRTM, GTOPO30 and ASTER GDEM but their accuracy differs from one to another and also selecting a small DEM size (high resolution) gives accurate information, but the analysis takes long time. This paper aims to analyze the impact of using different available DEMs on watershed geomorphological properties on order to provide guidelines for users to select the most suitable DEM that obtain an accurate analysis in less time. Three programs; watershed modeling systems: WMS, Global Mapper and Google Earth were used in this study. Three case studies were studied to check the accuracy of these models and select the most accurate one for application. Satellite images downloaded from Google Earth were used as a guide reference for the comparison due to their accuracy and high resolution. The results indicated that the SRTM model was more accurate (95%) for all case studies according to our comparison between its delineation and satellite images. ASTER GDEM is the second most accurate model with an accuracy of 87%, the GTOPO30's accuracy is 80%.
数字高程模型（DEM）是地形表面的数字模型或 3D 表示。有许多方法可以创建 DEM，例如激光雷达、立体摄影测量和地形地图。DEM 对于许多应用非常重要，例如提取地貌参数进行地貌学分析和建模水流进行水文学或物质运动分析。有许多网站可以提供 DEM，例如 SRTM、GTOPO30 和 ASTER GDEM，但它们的精度彼此不同，并且选择较小的 DEM 尺寸（高分辨率）会提供准确的信息，但分析需要很长时间。本文旨在分析使用不同可用 DEM 对流域地貌属性的影响，以便为用户提供指导，选择最合适的 DEM，以在更短的时间内获得准确的分析。本研究使用了三个程序；流域建模系统：WMS、Global Mapper 和 Google Earth。研究了三个案例研究，以检查这些模型的准确性，并选择最准确的模型进行应用。由于其准确性和高分辨率，从 Google Earth 下载的卫星图像被用作比较的参考指南。结果表明，根据我们对其划界和卫星图像的比较，SRTM 模型在所有案例研究中都更准确（95%）。ASTER GDEM 是第二准确的模型，精度为 87%，GTOPO30 的精度为 80%。
