Happy #MapInfoMonday, it's time for another tip and trick for the MapInfo Community.
It can sometimes be useful to convert a set of points into a set of polygons that divided the area between the points. We have
earlier looked at buffering. But buffers either overlap or underlap, they rarely assign the entire area between the input points.
In the example below, I have created 20 km buffers around my input points but you can see that there are areas where multiple buffers overlap, and there are also areas that aren't covered by a buffer.
To make sure the resulting polygons cover the entire area, you can create
Voronoi polygons instead. Voronoi polygons are also known as Thiessen polygons named after
Alfred H. Thiessen, an American meteorologist. Voronoi diagrams, or tesselations, were defined by
Georgy Voronoy. It will divide the area so that the area is assigned to the point closest to the area. This means you will end up with polygons that are of different sizes. Bigger polygons where you have points that are further apart, and smaller polygons where the points are closer together.
It is useful for dividing areas of responsibilities for field offices or possibly postal zones. It can also be used as a simple way to divide your sales territory into smaller sales districts where you assign each dealer the area that is closest to that dealer.
You find the
Voronoi option on the
Spatial tab in the
Create group. You can use a selection as input with the
Voronoi (Object) method. And the
Voronoi (Table) method allows you to pass in an entire table and create a new table as output.
First, you need to specify the table with your input, and where to store the result which can be an already open table, or you can create a new table for the result. I'll create a new table.
For the new table, I can specify how to display it, and to either create a completely new table structure or base the table structure on an existing table. I'll copy the table structure from the input table.
I am then asked to specify the name and location of the table to be created.
And finally, we get to the Voronoi procedure. The
Data Aggregation dialog allows you to copy over the attribute data from the input table to the output table.
When I hit the
OK button, MapInfo Pro will calculate the Voronoi polygons for the input points.
In the map below, you can see the resulting Voronoi polygons. Every point in each Voronoi polygon is closer to the input point inside that polygon than to any of the other input points.
As you can see from the map above, the extent of Voronoi polygons is similar to the extent of the input points. Often you want the Voronoi polygons to cover a specific area. To do this, you can set that area as your target.
Make sure the layer is editable, select one polygon from the editable layer, and use
Set Target on the
Spatial tab.
Now run through the process of creating your Voronoi polygons again, and you will notice that the resulting polygons will match up with your target area.
I hope you found this useful. Let me know if you have specific features of MapInfo Pro that you want me to cover in an upcoming
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Peter Horsbøll Møller
Principal Presales Consultant | Distinguished Engineer
Precisely | Trust in Data
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