Cell Statistics (e.g. mean or standard deviation across rasters) ( requires Spatial Analyst extension)

“Cell Statistics” is a function from the Spatial Analyst that allows you to calculate several statistical operations as derived from multiple rasters, i.e: minimum, maximum, mean, range, sum, standard deviation or median values of each grid from a group of rasters. The output is a new raster containing the statistic result for each cell corresponding to the calculation which has been derived from the specified cells beneath it. E.g. This is often used when trying to create a standard deviation map from e.g. 10 build models in order to provide spatially relevant values of variance (i.e. a map of error margins).

1. Go to "Cell Statistics" in the drop down menu from the Spatial Analyst toolbar
2. Add the relevant raster layers you would like the calculation to include to the right-hand pane
3. Select the statistic you wish to calculate and press ok.
4. (if the output is only temporary you must also make this permanent. See merging rasters step 10 for how to do this)