Questions tagged [voronoi-thiessen]

Thiessen polygons are polygons (generated from a set of points) whose boundaries define the area that is closest to each point relative to all other points. Thiessen polygons are mathematically defined by the perpendicular bisectors of the lines between all points and are created by means of a triangulated irregular network (TIN) structure.

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27
votes
2answers
33k views

Converting point sets to polygon boundaries?

I'm trying to convert sets of points to their respective polygon boundaries. I think this is something like a Voronoi diagram or Convex Hull, but not quite. I'm sure there's a technical term for it, ...
12
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1answer
5k views

How to use ST_DelaunayTriangles to construct a Voronoi diagram?

(edit 2019) ST_VoronoiPolygons available since PostGIS v2.3! With PostGIS 2.1+ we can use ST_DelaunayTriangles() to generate a Delaunay triangulation, that is a dual graph of its Voronoi diagram, and,...
18
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2answers
10k views

Is it possible to create Thiessen polygons around nodes in QGIS?

Is it possible to create Thiessen polygons around nodes in QGIS? e.g. http://en.wikipedia.org/wiki/Voronoi_diagram
36
votes
5answers
21k views

How best to fix a non-noded intersection problem in PostGIS?

I'm using a PL/R function and PostGIS to generate voronoi polygons around a set of points. The function that I am using is defined here. When I use this function on a particular dataset I get the ...
18
votes
1answer
4k views

Voronoi polygons that run out to infinity?

I have been working on implementing the voronoi.py script (Bill Simon's translation of Steve Fortune's code). According to the QGIS link it is basically the same code that I am working with, but the ...
5
votes
2answers
10k views

Thiessen Polygon delineation within a Feature

I am trying to create Thiessen (Voronoi) polygons, based on points within a defined shapefile extent. The output should be inclusive to the feature. The output I receive now is the rectangular area ...
12
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3answers
3k views

Constructing Voronoi diagram in PostGIS

I'm trying to construct voronoi diagram from grid of points using modified code from here. This is SQL query after my modifications: DROP TABLE IF EXISTS example.voronoi; WITH -- Sample set of ...
8
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2answers
4k views

Extracting centerline of a Complex-Polygon in PostGIS/Python

Any idea how to extract the centerline of the following polygon (Fig1) using PostGIS functions or Python modules? I was trying Voronoi Function but thats not helpful for this kind of shape. I want ...
12
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4answers
5k views

Create voronoi diagram from line segments

I'm looking for a way to create a voronoi diagram based on line segments instead of points. See the example below (taken from this presentation). Ideally I'd like something I can script from Python, ...
7
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2answers
5k views

R function for Thiessen Polygons

For a point data set with temperature data I have, I want to create their Thiessen Polygons in R. So far, the only algorithm I have found is that of Carson Farmer (http://carsonfarmer.com/2009/09/...
6
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1answer
520 views

Splitting overlap between polygons and assign to nearest polygon using PostGIS?

My question is quite related to the unanswered Split overlap between polygons into disjoint sets except I'm not using shapely, I'm using PostGIS 2.4 on PostgreSQL 10. I have a table containing ...
6
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0answers
904 views

Constructing a Voronoi diagram using a complicated travel time metric

I have in my possession four sets of shapefiles: 1. Locations (points), around 1000 2. Roads (lines), each road has a speed attribute 3. Terrain (polygons), each zone also has a speed attribute 4. ...
1
vote
1answer
99 views

Constructing Voronoi Polgon and Applying Nearest neigbour in it

I am learning QGIS 3.XX and currently working on Voronoi Polygons. I have three layers Point layer Building Layer Population CSV file. These points layer are basically water tanks and building ...
12
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4answers
953 views

Create mosaic like Voronoi Diagram from disjoint polygons

The illustration below shows the problem: as in (a) I have a set of disjoint polygons, as geometries in PostGIS. I need something like (b), the "mosaic" of this set of polygons, building it by a "...
11
votes
2answers
1k views

Is there a described GIS method for creating catchment areas based on nearest driving distance?

ie. a combination of Voronoi polygons with isochrones, so that the Voronoi polygons are based on driving distance instead of Euclidean distance. Is there a name or a described method for this?
11
votes
3answers
830 views

Considering holes/constraints in Voronoi polygon creation in QGIS?

I am trying to create voronoi polygons in QGIS that would consider "holes" in the general domain. An example would be: I actually created the Voronois in this image using QGIS through the GRASS ...
1
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1answer
1k views

R: Voronoi tesselation from long/lat data?

I want to create a SpatialPointDataFrame and Voronoi Tesselation from my .csv data downloaded from EPA, available here: http://uloz.to/xboQc7cu/no2-calif-csv I convert my data in SPDF format in 2 ...
13
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3answers
3k views

What does buffer mean in QGIS Voronoi dialog?

Could you explain what "buffer" does in the Voronoi dialog i.e. what does the number stand for?
5
votes
4answers
1k views

What Is The Ideal Workflow To Map (British) Postcode Territories

I'm looking for the best workflow for mapping postcodes and calculated territories, but being relatively new to mapping I'm struggling on a few details and also the best practices for displaying these ...
4
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0answers
180 views

Voronoi Polygon Algorithm seems to exclude a Point from processing

I am using the QGIS (2.8.1) Voronoi Polygons Algorithm on a point shapefile. See image below, the red triangles are the points I am using. The resulting polygons miss a part (around HP87). Any ...
1
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0answers
273 views

Voronoi / Thiessen polygons doesn't create a part for 1 of 4 input points

I am using QGIS to create Voronoi / Thiessen polygons for 4 rain gauges. I am having issues with both the QGIS 'Voronoi polygons' tool and the Grass equivalent 'v.voronoi' where one of my 4 points ...
5
votes
0answers
400 views

The drawing of Thiessen/Voronoi polygon boundaries - are the bisecting lines truly perpendicular?

I am concerned with how QGIS (version 2.8.1) and ArcGIS (version 10.0) draw "perpendicular bisecting lines" when Thiessen/Voronoi polygons are created. When using either program to create these ...
3
votes
4answers
802 views

Calculating Voronoi Diagrams for polygons

There are a variety of good algorithms for generating the Voronoi polygons or their complement, the Delaunay Triangulation for a set of points. My question is simply, is there an algorithm for ...
2
votes
0answers
2k views

Create Voronoi/Thiessen polygons in QGIS around 3 points

Running QGIS 1.8.0 I have three bus compounds. I would like to generate Voronoi/Thiessen polygons around those three points. Following Voronoi/Thiessen adding an all school points will allow us to ...
2
votes
0answers
235 views

Is there any way to set a processing extent for QGIS:Voronoipolygon?

I was playing around with the QGIS:voronoipolygons command line function from QGIS and noticed that there was no option for setting the processing extent. This causes QGIS to pick the minimum extent i....
0
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1answer
156 views

Thiessen Ploygon Bifurcated Areas Calculations

I have a SewerGEMS network of a sewerage scheme for a town. The town is divided into 17 wards having different population densities in (Population/Hectare). There is an AutoCAD drawing showing the ...
0
votes
1answer
77 views

Symbology: different ways to display categorised data QGIS 2.16 [closed]

I have a database of 100 entries which has been categorised using a column of data that has 20 categories which essentially breaks up my map into 20 regions. I'm seeking advice on ways how to create ...