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Frequent Contributor
Posts: 86
Registered: ‎05-17-2016
Accepted Solution

Theissen/Voronoi Plygons

Hello,

 

Is it possible to create Theissen Polygons from the functional attribute in GeoMedia?

 

Regards,

 

Kevin.

Technical Evangelist
Posts: 501
Registered: ‎09-11-2015

Re: Theissen/Voronoi Plygons

Hello Kevin,

 

this cannot be done via functional attributes unless you create your own FA package. But there is a support for this in GM Grid.

 

Pavel

Technical Evangelist
Technical Evangelist
Posts: 218
Registered: ‎02-03-2016

Re: Theissen/Voronoi Plygons

Pavel is correct that the Grid functionality of GeoMedia Desktop is where you would find this capability today.  Regarding doing it via functional attributes, this would not be possible even for a custom function package.  Functional attributes work on only one feature instance at a time, and a Voronoi polygon can be computed only in the context of the complete set of points.  Therefore this would have to be a separate pipe and command.  There are no immediate plans for this, but posting the Idea to the Ideation board would be a good idea.  - Hal

Staff
Posts: 108
Registered: ‎05-26-2016

Re: Theissen/Voronoi Plygons

Thiessen/Voroni polygons require the set of points to be triangulated.

 

If you then have the triangles, you can use Functional Attributes to calculate the Thiessen segments and hence the polygons.

We used to have a product that done this well, GeoMedia Terrain, but its long gone. And some Photogrammetry products still do it.
Or use something Third party.

 

Anyway if you cannot create triangles, but your point dataset is small, you can digitize triangle polygons between points,
or just simply digitize triangles and dynamicaly create the Thiessen edges using Functional Attributes.

 

FA 1. CENTROID(Input.Geometry) -  get centroid of triangle
FA 2. SEGMENTS(Input.Geometry) -  get segments of triangle

 

The centriod and segments inherit the same ID as the triangle polygon ID

 

FA 3. CENTERPOINT(Input.tiangle_segments) - get centrepoint of segment edges

 

The centrepoints inherit the same ID as the triangle polygon ID also

 

FA 4. Do an Aggregation of the Segment Centrepoints (Summary) with the Centriod of Triangle (detail)
      Do the  only Attribute Aggregation of ID/ID
      and Output as CREATEPOLYLINE(Input.segment_centrepoints, FIRST(Detail.tiangle_centroid))

 

You will now get the Theissen polygon edges for existing triangle polygons or dynamically as you digitise or edit them.

Staff
Posts: 108
Registered: ‎05-26-2016

Re: Theissen/Voronoi Plygons

Just want to confirm, using CENTRIOD or CENTREPOINT to calculate the centre of the triangle is only an approximation method. The Actual point is the "Circumcentre of the Triangle" thats required. you would need a few more FA's to get this to produce an accurate Thiessen polygon.

Frequent Contributor
Posts: 86
Registered: ‎05-17-2016

Re: Theissen/Voronoi Plygons

How can it be done using GRID in GeoMedia? Which tool performs the process that gives voronoi maps/theissen polygons from from point datasets?

 

 

Regards,

Kevin.

Frequent Contributor
Posts: 131
Registered: ‎02-17-2016

Re: Theissen/Voronoi Plygons

On the Grid tab, rasterize the point feature class. Then under Classification is the Thiessen function.

Highlighted
Frequent Contributor
Posts: 86
Registered: ‎05-17-2016

Re: Theissen/Voronoi Plygons

Thanks Goodman. Didn't kow the tool is that simple to locate.

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