9.3. GIS Book: Creation of slope maps

Slope is the main factor that determines and differentiates the shapes of the relief. Given two points of different altitudes, the slope of the terrain is understood to be the mathematical ratio determined by the proportional relationship between the difference in altitudes and the horizontal distance between the two points (Hernández, 1998).

The slope can be expressed in percent or sexagesimal degrees. To create a slope raster, a DEM is required as input information, and the Slope tool is used to generate the slope raster, which is located at:

ArcToolbox > Spatial Analyst Tools > Surface > Slope

Figure 41. Configuration of Slope tool parameters

The Slope tool configuration (Figure 41) is described as follows:

  • Input raster: Select the layer containing a DEM.
  • Output raster: Select a directory or geodatabase to store the slope raster file.
  • Output measurement: Select “DEGREE” for decimal degrees, and “PERCENT_RISE” for percentage.
  • Z factor: This is an optional factor, used to match Z linear units to XY linear units.
Figure 42. Raster of slopes in degrees

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