针对现有的数字高程模型(DEMs)在自动提取虚拟河网过程中易受洼地、平原地区影响,产生不连续的或平行的错误河网的问题,本文基于Arc Hydro Tools,阐述了地表校正(Agree算法)和河道烧录(Stream burning)方法提取虚拟河网的关键步骤和基本思路,并以环渤海地区为例,分析了有(无)河网辅助信息下,河网提取结果的准确度。研究结果表明,增加辅助信息更有助于提高虚拟河网的精度和准确性,且河道烧录方法在虚拟河网的提取上比Agree算法更有优势。由于环渤海研究区平原面积广大,对提取结果有较大的影响,提取结果的精确度不高。针对这一问题,本文综合河道烧录和地表校正(Agree 算法)的特点,提出一种河网提取的改进思路,并选取滦河流域作为验证区。通过对比,改进后的河网提取结果与中国实际河网分布较为吻合,说明该改进思路是较为合理、可信的。
When extracting digital stream network based on digital elevation models (DEMs), wrong information such as parallel river channels is often generated due to the topographic effects like plains and sinks. In view of this, two algorithms including "Stream burning" and "Surface reconditioning"(Agree algorithm ) using Arc Hydro tools in ArcGIS environment were employed in this study based on Shuttle Radar Topography Mission (SRTM) DEMs, released by NASA and NIMA, to extract digital drainage networks in the Bohai Sea Region. Actual three-level stream network data in China in both vector and raster formats were available from National Geometrics Center of China (NGCC) and then were used to compare with the stream network extracted based on SRTM DEMs. The results showed that the known stream network information is helpful to extract the stream network. Without aid of the known stream network, there were only two streams consistent with the known stream network based on traditional method and the extraction precision was at low level. Comparatively, using "Agree algorithm", several digital streams tallied with typical known stream network, indicating that "Agree algorithm" can produce more precise results than by traditional method. To improve the extraction precision of digital stream network, "Stream burning" was further employed. This algorithm generated more detail of digital stream network and less parallel river channels. The overall results illustrated that "Agree algorithm" and "Stream burning" were more sophisticated than traditional method in terms of digital stream network extraction. It should be noted that the results of extraction of digital stream network in this study were not perfect due to the extensive existence of plains in the study region. Therefore, the characteristics of two algorithms, namely "Agree algorithm" and "Stream burning" were synthesized into a new method to extract the drainage network. Luanhe River Basin was finally chosen to validate the result derived from such a new method.
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