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Zonal Statistics with ArcGIS

The zonal statistics tool allows you to calculate various statistics for one or more previously defined zones, based on the data of an existing raster image.

For example, in a set of plots or watersheds it is required to know the average slope, or minimum and maximum elevation. In the first case, this information can be obtained from a slope raster, in the second case with a digital elevation model (DEM). The zonal statistics tool analyzes each raster, and returns the result in a table that contains the statistical values for a given zone.

The statistics according to the type of input data that can be calculated are the following:

  • Output data type
  • Majority
  • Maximum
  • Mean
  • Median
  • Minimum
  • Minority
  • Range
  • Standard deviation
  • Sum
  • Variety
  River profiles in QGIS

To run the zonal statistics tool go to the following address:

ArcToolbox > Spatial Analyst Tools > Zonal > Zonal Statistics as Table

Input raster or feature zone data.- Enter a polygonal layer or a raster that contains the study areas (watersheds).
Zone field.- Select the field that defines each zone.
Input value raster.- Select the raster image (for this example a digital elevation model).
Output table.- Select the name and directory for the result table.
Statistics type.- You can choose all available statistics or one in particular.

Once the process is executed, right click on the generated table open its attributes table to see the results.

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