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:
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.