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Abstract

Geographic Information Systems (GIS) offer a cost-effective way to analyze and inventory land and environmental resources. There are many attributes that can be displayed and analyzed in GIS. One of these attributes is slope, which can be calculated from a digital elevation model (DEM). Slope is an important factor in a variety of models used in land analysis as well as land use and management. There are several different mathematical computational algorithms used to calculate slope within a GIS. Eight different slope calculation methods were investigated in this study. These methods were used to calculate slope using 10-m, 30-m, and 100-m DEMs. There were two phases of analysis in this study. The first phase was a cell-by-cell comparison of the eight slope algorithms for all three DEMs to obtain an understanding of differences between the calculated slope methods. The second phase was to determine the method that calculated the most accurate slope from a 10- m, 30-m, and 100-m DEM, by comparing calculated slope to actual slope value. All methods underestimated slope for the 100-m DEM with a mean slope difference ranging from 9.28% to 11.085%. For the 30-meter DEMs all the slope methods underestimated slope, with a mean slope difference range from 0.21% to 4.18%. The 10-meter DEM mean slope difference ranged from -2.63% to 1.82% for the cell slope methods. For all methods, steeper slopes, greater than approximately 40%, were underestimated when slope was calculated from a DEM.

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