9.4. GIS Book: Reclassifications

The Reclassify tool allows the values of a raster to be reclassified; that is, it replaces the current values of each cell with new information. Data can be reclassified from any variable stored in raster format (slope, elevation, precipitation, temperature, etc.).

Practice: Build a slope map based on the classification proposed by FAO (2009) and group the values of the slope raster into classes (e. g. Figure 42). Table 4 presents eight classes, each of which contains the slope values in percent and decimal degrees.

Table 4. Slope gradient classes

To run the reclassification, open the Reclassify tool at the following address:

ArcToolbox > Spatial Analyst Tools > Reclass > Reclassify

Figure 43. Configuration of parameters of the Reclassify tool

In the pop-up window, the parameters described below (Figure 43) must be configured:

  • Input raster: Select the layer containing the slope raster.
  • Reclass Field: Select the field containing the slope values. By default, this is usually VALUE.
  • Reclassification: Within this section clicking on the Classify button opens a sorting window where class values can be adjusted. In the Classification section of the classification window you can select the classification method and define the number of classes (8). In the lower right-hand corner of the Break Values section, you can manually enter the limits of each class (e. g. gradient values as a percentage of Table 4).
  • Output raster: Select a directory or geodatabase to store the reclassified slope raster file.
Figure 44. Raster of reclassified slopes

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