DEM-based slope unit derivation

This paper focuses on slope unit derivation from DEM by object-based image analysis. A landform classification system consisting of ridge, valley, slope unit, and flat terrain classes is firstly constructed considering the detailed characteristics of slope unit. Based on the classification system, a procedure for slope unit derivation from DEM, which takes into consideration the topographic factors including slope gradient, slope aspect and curvature, is designed within multi-scale OBIA framework. The method to determine the optimum segmentation scale by COLV is also introduced. A case study of Shenzhen is carried out to verify the feasibility and accuracy of the designed procedure. The results of the case study shows that when the scale parameter is 20, the derived slope units remarkably denote the detailed landform structure and the bounds of the derived units are largely consistent to the concave and convex terrain bounds.