Tin - Thiessen Polygons

    THIESSEN constructs Thiessen polygons around a set of points. Thiessen polygons divide space such that each location is allocated to the nearest control point. The polygons define the regions which are dominated by each point. A division of space into polygons of this nature is also known as a Voronoi Tessellation.

    THIESSEN first requires you to specify if the points for polygon construction are in a vector file or an image file, and to input the name of that file.
The identifiers for the points are integer numbers, with each point assigned a different identifier. This is so the output image will code each cell with the identifier of the point to which it belongs. Thiessen polygons are formed by the regions of common identity.

    Then, THIESSEN requires you to input a name and title for the output image. If a vector file is used for point input, specify the desired file type and data type of the resulting image. The default file type is ASCII and the default data type is integer. It then displays the minimum and maximum X and Y coordinates and requires you to enter the number of rows and columns to span the region.