Please use this identifier to cite or link to this item:
|Other Titles:||The Effect of Flow Direction Algorithms and Threshold Values on Extracting Stream Networks from Digital Terrain Model|
Department of Geography, NTNU
本研究以台北市雙溪流域為試區，使用5 m 網格解析度數值地形模型，配合6 種流向演算法
與12 等級集流閥值，進行河川網路自動化萃取，並對照1/5,000 地形圖之河流線，輔以人工判釋，
間差異極小，但與人工測繪基準圖層仍普遍存在1 至8 個網格之河道對位誤差。綜合評估結果，
Traditionally, stream networks were delineated manually in hydrologic analysis. Though certain degree of accuracy can be achieved, the process requires large amount of time. In comparison, deriving stream networks from grid based digital terrain model (DTM) is more efficient than the manual process. However, the accuracy of the results varies with different flow direction algorithms and threshold values. This study selected the Shuangshi watershed as the study site in Taipei, and utilized digital terrain models with grid size 5m to derive stream networks automatically. Six different flow direction algorithms and twelve threshold values were applied in this study, and the resultant stream networks were manually compared to the stream networks found on 1/5,000 topographic map. The results indicate that: (1) The commission error is much higher in 1st order stream and 2nd order stream, and more effective on stream width when Multiple-flow direction algorithm and D-infinity flow direction algorithm were applied; (2) Different threshold values have more effective on the stream length, and the commission error decreases as the threshold value increases, where the effects on stream width are not prominent; (3) Overall, though the difference between flow direction algorithms is mainly in deriving the width of streams, and the extracted stream centerlines are similar, 1~8 grid-length bias remain existed when comparing to the stream networks shown on the topographic maps. The results obtained from the Shuangshi watershed show that the performance of flow direction algorithms is different when stream order changes. For accurate estimation of stream width, further investigations are needed.
|Appears in Collections:||地理研究|
Files in This Item:
There are no files associated with this item.
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.