Evaluation of the accuracy of extraction of slope and length based on DEM of GF-7 satellite

Faculty of Geographical Science, Beijing Normal University

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The National Natural Science Foundation of China (No.42177308)

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    [Purpose] Slope and slope length are essential topographic factors affecting soil erosion process, and thus should be accurately estimated for erosion modelling. The Gaofen-7 satellite is known for its capacity of high-precision elevation measurement, and therefore holds a great potential for a high-quality extraction of the topographic factors such as slope and slope length. This study aims to evaluate the performance and accuracy of Gaofen-7 satellite in terms of deriving slope and slope length. [Methods] DEMs generated from the GF-7 satellite images, 1:10 000 topographic map and LiDAR images were processed using LS calculation tool to derive slope and slope length for four small watersheds in WuBu County, Shaanxi Province. Performance indicators including correlation coefficient (r), relative bias (RE) and absolute bias (AE) were used to estimate the discrepancy between different data sources. [Results] The results show that: (1) the elevation data of the three sources have extremely strong correlations (r>0.956). Compared with the topographic map and LiDAR, the watershed-average slope derived from GF-7 is lower by 7.50%~9.02% while slope length is higher by 1.83%~19.35%. However, the area distributions of slope length and slope derived from the three data sources have no significant difference. (2) Comparing the results of slope and slope length, the discrepancy in slope (RE: 16.46%~44.26%) derived from different sources is significantly lower than that (RE: 75.25%~140.87%) in slope length. (3) The discrepancy between different sources is enhanced in gully areas (RE of slope: 15.48%~56.63%; RE of slope length: 50.02%~130.79%), while being decreased in inter-gully areas (RE of slope: 21.28%~63.61%; RE of slope length 93.01%~192.51%). [Conclusion] It is feasible to obtain areal grading characters of slope or slope length and slope of specified locations using DEMs generated from Gaofen-7 satellite, while the results of slope length for specified locations are less reliable. In conclusion, the Gaofen-7 satellite has a great advantage in describing the spatial distribution of slope length and slope at the watershed scale, while being less capable of capturing slope length and slope at a specific site.

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  • Received:June 26,2023
  • Revised:August 12,2023
  • Adopted:August 31,2023
  • Online: January 27,2024
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