THSNPOLY

Description

Creates a Thiessen polygon channel (Voronoi diagram) from an input point layer.

Parameters

Name	Type	Length	Value range
InputPoints: Input vector segment *	Vector port	1 - 1
InputArea: Georeferencing segment	GEO port	0 - 1
Output: Output Thiessen polygons *	Vector port	1 - 1
Source Attribute	String	0 - 1	COPY | JOIN Default: COPY

* Required parameter

Parameter descriptions

InputPoints: Input vector segment

Specifies the vector segment that contains the point layer for which the Thiessen polygons will be constructed.

InputArea: Georeferencing segment

Specifies the georeferencing of the output raster channel, including the projection, geographic extents, and resolution of the resulting output channel.

If this parameter is not set, the projection of the polygon channel will be the same as that of the input point segment and the geographic extents of the polygon channel will be 10 % greater than the extents of the points segment.

Output: Output Thiessen polygons

Specifies the vector segment to receive the output Thiessen polygons.

Source Attribute

Specifies whether the attributes from the source layer are copied or joined to the point layer.

Details

THSNPOLY takes an input point layer and generates a Thiessen polygon layer. A Thiessen polygon, or Voronoi diagram, defines a polygon about a point such that all locations within the polygon are closer to that point than to any other point. In the THSNPOLY function, one polygon is generated for each input point.

The attributes for the polygon layer, which include area, perimeter, and the attributes from the original layer, are either copied to the new layer or joined (linked) to the original layer. If joined, an attribute named "SourceID" will be added as the join field.

The extents of the generated layer are determined from either the input point layer (+ 10%) or from an optional georeferencing input.

Raster Thiessen polygons can be generated using the GRDPIN function, although you must enter a parameter value of 1 for "Number of sample Points".

This function can be used to model zones of influence.