一种改进的DEM数字水系简易提取方法研究

利用DEM提取数字水系的过程分为填洼、流向计算、汇流累积量计算和设定阈值提取水系,其中以填洼和计算各单元的汇流累积量最为费时。相比与Jenson和Domingue(JD)、Planchon和Darboux(MV)填洼算法,L.Wang和H.Liu(WL)填洼算法具有原理简单、运行速度快等特点。但是,WL算法未对平区高程进行修正,增加了后续相关算法的复杂度。本文通过将JD和MV算法中的微小高程增量引入WL算法,建立改进的WL算法,可以有效地解决该问题。在汇流累积量的计算过程中,受WL填洼算法思想的影响,构建了逆向WL汇流累积量算法,该算法一改传统的流向追踪思想,通过对填洼后DEM进行升序排序,可逐步对每一栅格进行计算。该算法原理简单,易于实现,对单流向和多流向方法均具有很强的适应性。利用SRTM、GDEM源数据进行了示例计算,并将结果与ARC/INFO软件结果进行了对比,结果表明该方法合理、准确。

A DEM based-improved simple method for extraction of digital water system

The process of the extraction of digital water system with digital elevation model（DEM）is diveided into the sub-processes of depression-filling，flow-direction calculation，confluence accumulation calculation and threshold setting for extracting water system； in which depression-filling and confluence accumulation calculation of all the units are most time consuming. Compared with the Jenson and Domingue（J&D）and Planchon and Darboux（M&V）depression-filing algorithms，L.Wang and H.Liu（W&L）depression-filling algorithm has the features of simple principle，high operation speed，etc. However，W&L algorithm does not make any revisions on the flat-zone，and then increases the complexities of the successive relevant calculations. This problem can be effectively solved through introducing the micro-increments of elevation in J&D and M&V algorithm into W&L algorithm and then establishing an improved W&L algorithm. By changing the conventional concept of flow tracking，this algorithm can calculate each grid step by step through sorting the DEM after depression-filling in an ascending order. As the principle of this algorithm is simple，it is easy to be realized and strongly adaptable for the single flow direction and the multiple flow direction methods. With SRTM and GDEM source data，a case calculation is made and its result is cpmpared with that from the software of ARC/INFO. The result shows that it is reasonable and accurate.