ETG_ZonalStatistics

Zonal Statistics

Analyses the values of a raster within each polygon of the input polygon dataset. Calculates statistics for each polygon and adds them in the attribute table of the output.

Inputs:

A polygon feature class
A raster dataset for which the statistics will be calculated.
A prefix for the field names. The function adds several fields to the polygon attribute table. The prefix will help the user to calculate the statistics of several rasters for the same polygons and add the results to the same attribute table. For example the user wants to calculate statistics for the slope and elevation for a polygon dataset. This requires two different rasters (Elevation and Slope). The function needs to be run twice
- on the Elevation raster with prefix "EL"
- on the Slope raster with prefix "SL"

Outputs:

A polygon dataset - a copy of the original polygons
All the original attributes will be preserved.
Depending on the type of the raster used, the following statistics will be calculated for each polygon and added to the attribute table of the output (XXX in the field names below replaces the prefix used in the function).
- Integer and Floating point rasters
  - XXX_Count - the number of cells within a zone
  - XXX_Sum - the sum of the cell values within a zone
  - XXX_Min - the minimum value within a zone
  - XXX_MinX - the X coordinate of the cell with minimum value within a zone
  - XXX_MinY - the Y coordinate of the cell with minimum value within a zone
  - XXX_Max - the maximum value within a zone
  - XXX_MaxX - the X coordinate of the cell with maximum value within a zone
  - XXX_MaxY - the Y coordinate of the cell with maximum value within a zone
  - XXX_Range - the range of values within a zone
  - XXX_Mean - the average of the values within a zone
  - XXX_STD - the standard deviation of the values in a zone
  - XXX_Median - the median value in a zone
- Integer rasters only
  - XXX_Major - the majority value (the value that appears most timesin a zone).
  - XXX_Minor - the minority value (the value that appears least times in a zone).
  - XXX_Variety - variety (the number of unique values in a zone).

Notes:

If the input polygon dataset has multi-part polygons, they will be exploded into single part polygons and the statistics will be calculated for the single part polygons.

Running Programmatically

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Parameters

Expression	Explanation
Function Name	ZonalStatistics
<InputPolygons>	A String - full path to the Input Polygon dataset.
<OutputPolygons>	A String - the full path to the output polygon layer.
<InputRaster>	A String - full path to the input raster dataset.
{Prefix}	A String (maximum 3 characters) representing the prefix. See description above.

Running the function

ETSPath used in the table below is the full path to ETSRun.exe (E.G. "C:\Program Files\ETSpatial Techniques\ETSurface\ETSRun.exe")

InputRaster

Language	Syntax
Python	subprocess.call([ETSPath, "ZonalStatistics", "InputPolygons", "OutputPolygons", "InputRaster", "Prefix"])
.NET using ETSRun.exe	StartInfo.FileName = ETSPath StartInfo.Arguments = "ZonalStatistics" "InputPolygons" "OutputPolygons" "InputRaster" "Prefix"
.NET using ETSOutX.dll	ZonalStatistics(InputPolygons, OutputPolygons, InputRaster, Prefix)
ArcPy	arcpy.ZonalStatistics("InputPolygons", "OutputPolygons", "InputRaster", "Prefix")

Notes:

<> - required parameter
{} - optional parameter
See examples for Python , .NET or ArcPy
The argument separator for StartInfo.Arguments is space. If a string might contain a space, you need to double quote it.

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