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description:
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The land surface forms were identified using the method developed by the Missouri Resource Assessment Partnership (MoRAP). The MoRAP method is an automated land surface form classification based on Hammond’s (1964a, 1964b) classification. MoRAP made modifications to Hammond’s classification, which allowed finer-resolution elevation data to be used as input data and analysis to be made using 1 km2 moving window (True, 2002; True and others, 2000). While Hammond’s methodology was based on three variables, slope, local relief, and profile type, MoRAP’s methodology uses only slope and local relief (True, 2002). Slope is classified as gently sloping or not gently sloping using a threshold value of 8%. Local relief is classified into five classes (0-15m, 16-30m, 31-90m, 91-150m, and >150m). Slope classes and relief classes were subsequently combined to produce eight land surface form classes (flat plains, smooth plains, irregular plains, escarpments, low hills, hills, breaks/foothills, and low mountains). Sayre and others (2009) further refined the MoRAP methodology to identify a new land surface form class, “high mountains/deep canyons”, by using an additional local relief class (>400 m). The Africa implementation used a 90-meter elevation dataset which was created by void-filling and re-sampling the 30-meter SRTM elevation data provided by the National Geospatial- Intelligence Agency. |