Extract Raster Zonal Statistics

Purpose

The tool is meant for extracting statistics from raster datasets at the zones defined by the selected polygons.

Description

The Extract Raster Zonal Statistics tool requires two input datasets, a raster dataset and a polygon dataset. Statistical summary of the raster dataset values covered by the zonal polygons will be written to the same input polygon as new attributes or output as a new table.

Usage

• Select the "Extract Raster Zonal Statistics" tool from XTools Pro Raster Tools.

• Select input raster to extract zonal statistics from.

• Select polygons defining zones for which statistics will be extracted from the input raster.

• Select if the extracted statistics will be appended as new fields to the input polygons attribute table or a new table will be created.

• In the latter case specify the new output table and select the Zone ID field from the input polygons.

• Select statistics for extraction and modify output field names if required.

• Press Run to extract zonal statistics.

Statistics parameters

The following parameters can be extracted:

• Count - count of raster cells that belonged to the input polygon.

• Max - the largest value of all raster cells within the input polygon.

• Min - the smallest value of all raster cells within the input polygon.

• Mean - the average value of all raster cells within the input polygon.

• Range - the difference between the largest and the smallest values of all raster cells within the input polygon.

• Standard deviation - the standard deviation of all raster cells within the input polygon.

• Sum - the total value of all raster cells within the input polygon.

Default field names for statistics parameters can be changed.

Notes:

• As well as ArcMap Zonal Statistics tools, XTools Pro Extract Raster Zonal Statistics tool calculates the raster values standard deviation assigned to all cells in each input polygon by the formula based on the entire population (the "N" method), not a sample (the "N-1" method):
  
  The formula is equivalent to STDEVP method used in Microsoft Excel.

• If selected input polygons do not overlap any part of the input raster containing data (for example, polygons cover only NoData cells or do not overlap raster layer at all), then "-999" value is written to the fields in the output table indicating NoData. Besides, same "-999" values are assigned to the non-processed polygons in cases when selected features are used for processing.

• If Zone ID field contains non-unique values, the statistics won't be grouped.