Pitney Bowes MapInfo Vertical Mapper - Manual (Page 189)

Chapter 11: Using Natural Neighbour Analysis
User Guide
187
The following section describes the two main procedures in Vertical MapperSurface Analysis that
make use of natural neighbour relationships: building Voronoi diagrams from point tables and
calculating point density.
Creating Regions from Points (Voronoi)
Using the Voronoi technique, you can generate a region around each individual data point. The
resulting network of regions is often referred to as a Voronoi diagram.
Before running to completion, the point table is checked to ensure that no coincident points are
present. If coincident points are found, an error message will appear warning you that the input table
contains coincident points. You can edit the table or use data aggregation tools to fix this problem.
The extended error code contains the row ID of the first coincident point found.
1. From the Vertical Mapper menu, choose the Natural Neighbour Analysis >Create Regions
From Points (Voronoi) command.
2. From the Create From Table list, choose a table of points from the list and click the Next button.
All data fields present in the point table are assigned to the new Voronoi region table.
3. In the Voronoi Options dialog box, choose the required settings to control the manner in which
the Voronoi diagram is created.
4. Click the Finish button.
The Voronoi regions table opens in a new Map window.
Exploring the Voronoi Options Dialog Box
The most critical area of the Voronoi diagram is the outer margin where no points are present to
control the formation of the outermost polygons.
The Boundary Smoothness section—enables you to determine the number of line segments that
are used to construct the corners of the outer hull of the diagram. The finer the setting is, the
smoother the corners will become.
The Set Distance box in the Hull Boundary Width section—enables you to set the distance, in map
units, of the outermost polygon edge from the outer points. Since no points are present beyond the
margin that controls the creation of polygons, this setting restricts the construction of polygon sides
to a fixed distance from each outermost point (see the next two figures).