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2010, Vol. 12 Issue (5) :700-706    DOI:
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Analysis of Slope Length Extracted from Grid-based Digital Elevation Model in ArcGIS Environment
JIN Bei, LIU Xuejun, ZHEN Yan, LI Haoshu
Key Laboratory of Virtual Geographic Environment,Nanjing Normal University,Ministry of Education,Nanjing 210046,China

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Abstract Slope length,which describes the distance of flow path from origin point,is often a vital terrain parameter in soil and water conservation,soil erosion and environmental assessment studies.A common method of obtaining estimates of slope length is based on flow directions from grid-based Digital Elevation Model(DEM) in Geographical Information System(GIS) software.This method leads to slope length estimates with variable accuracy,which depends on DEM error,DEM resolution,algorithms of flow direction and distance measurement.Error and resolution are determined for a given DEM,leaving only algorithms of flow direction and distance measurement.This thesis focuses on the effect of these two uncertain factors on slope length which is derived from DEM.Based on a series of rigorous calculation on a DEM of simulated gully network,the paper finds that the model of slope length in ArcGIS software is not suitable to calculate the slope length because the flow direction derived from D8 is deterministic and this makes the flow route become discontinuous.Although the error by which distances are calculated over raster structures is less than 8.9% and can be improved by statistical methods such as distance transforms,any method that used to low this error is meaningless if the flow direction is wrong.In order to test these conclusions,we applied non-cumulative slope length algorithm in the platform of ArcGIS for two different typical DEMs,including a sample data in ArcGIS and a 5m grid cell DEM of Jiuyuangou drainage basin in North Shaanxi Loess Plateau.Comparing with the lengths obtained from contour map,the former conclusions are verified.So,it is necessary to develop a new flow direction algorithm with vector character in order to improve the estimate accuracy of slope length derived from grid DEM.
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Articles by authors
JIN Bei
LIU Hua-Jun
JUAN Yan
LI Hao-Shu
KeywordsArcGIS   Digital Elevation Model(DEM)   slope length   error   flow direction     
Received 2009-08-31;
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JIN Bei, LIU Xuejun, ZHEN Yan, LI Haoshu.Analysis of Slope Length Extracted from Grid-based Digital Elevation Model in ArcGIS Environment[J]  , 2010,V12(5): 700-706
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