ThiessenPolygons

Build Thiessen Polygons

Builds Thiessen Polygons from a feature layer

Thiessen (Voronoi) polygons define individual areas of influence around each of a set of points. Thiessen polygons are polygons whose boundaries define the area that is closest to each point relative to all other points. They are mathematically defined by the perpendicular bisectors of the lines between all points

Inputs:

A feature layer (Point, Multipoint, Polyline, Polygon)

Outputs:

New polygon layer.
- If the Attach attributes option is selected, the attributes of the source features are transferred to the new attribute table.

Notes :

By default the Thiessen polygons are clipped to the extents of the input features. There is an option to buffer the extents rectangle before clipping with it.
The resulting feature class can be clipped (Clip Layer Wizard ) with any polygon layer to mach the shape of this layer.
The function should work with no problems on datasets with up to 6 million points.

Examples of use:

Defining trade areas
From a set of soil sampling points to define non overlapping polygons for each soil type

Example:

Thiessen - Buffer Distance = 0

Thiessen (Voronoi) polygons

Thiessen - Buffer Distance > 0

Thiessen (Voronoi) polygons

Running Programmatically

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Parameters

Expression	Explanation
Function Name	BuildThiessen
<input dataset>	A String representing the input layer. Must be of Polygon type.
<output dataset>	A String - the full name of the output layer.
{Buffer Distance}	A Double representing the distance to buffer the input extent (in the units of the spatial reference of the input dataset.
{Add Attributes}	A Boolean that indicates whether the attributes of the input features are to be transfered to the thiessen polygons.

Running the function

ETGWPath used in the table below is the full path to ETGWRun.exe (E.G. "C:\Program Files\ETSpatial Techniques\ETGeo Wizards\ETGWRun.exe")

Language	Syntax
Python	subprocess.call([ETGWPath, "BuildThiessen", "input dataset", "output dataset", "Buffer Distance", "Add Attributes"])
.NET using ETGWRun.exe	StartInfo.FileName = ETGWPath StartInfo.Arguments = "BuildThiessen" "input dataset" "output dataset" "Buffer Distance" "Add Attributes"
.NET using ETGWOutX.dll	BuildThiessen(input dataset, output dataset, Buffer Distance, Add Attributes)
ArcPy	arcpy.BuildThiessen(input dataset, output dataset, "Buffer Distance", "Add Attributes")

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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