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3
votes
3answers
181 views

How to count the sides or edges of a polygon?

I wondered if it is possible to determine the number of sides / edges (not vertices) that a polygon has. Imagine the following case. There is a shapefile with 10 polygons. Is there any way to ...
6
votes
1answer
158 views

How to use ST_DelaunayTriangles to construct a Voronoi diagram?

With PostGIS 2.1+ we can use ST_DelaunayTriangles() to generate a Delaunay triangulation, that is a dual graph of its Voronoi diagram, and, in theory, they have an exact and reversible conversion. ...
3
votes
1answer
145 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 ...
6
votes
2answers
345 views

What is the difference between Create Thiessen Polygons tool (ArcGIS) and Voronoi Polygons tool (QGIS)?

Is Thiessen polygons the same thing as Voronoi polygons? I am using ArcMap 10 and also QGIS 2.4 and I would like please to know the exact difference (If any) between the two methods.
2
votes
1answer
47 views

What is the correct cartographic projection to calculate a Voronoi tesselation?

I have a set of points with known geographic coordinates. I would like to compute a Voronoi tesselation from these points in order to obtain areas of influence. The geometrical area of each Voronoi ...
2
votes
3answers
131 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, ...
1
vote
1answer
51 views

Thiessen polygons of sub-districts to lie within district boundaries [duplicate]

I'm using ArcGIS 10.1 and am fairly new to it. I have the latitude and longitude of sub-districts, and wish to create Thiessen polygons of these sub-districts. I also have shapefiles for districts ...
2
votes
0answers
49 views

Iterative point feature removal based on Thiessen polygon values

The background is: I have point feature class and Thiessen polygons created based on it. I wanted to know for each point Thiessen polygon area value, so I have calculated Thiessen polygon area value ...
1
vote
2answers
124 views

Creating Thiessen polygons gives ArcGIS ERROR 000537 error in converting points to Voronoi Polygons?

I have a problem with creating Thiessen polygons for a set of points. I am creating them with Create Thiessen Polygons tool in ArcGIS 10.1). I am able to create them in a few steps (for parts of the ...
1
vote
1answer
76 views

Smoothly interpolating Polygons from set of coordinates?

I'm still quite new to QGIS and I'm using it to display and analyze my soil data. I have point information on the distribution of the soils in a specific area and I need to create a soil map from ...
1
vote
1answer
104 views

Get Coordinates of Voronoi Polygon Vertices [duplicate]

Is there any chance to get the exact coordinatas of the voronoi polygons? I am using Qgis software and I have the "center" (redpoint) of the polygons and I would like to export the polygons corners ...
4
votes
0answers
152 views

How to do Manhattan Voronoi on QGIS?

I've spending last two weeks trying to discover how to do a Manhattan Voronoi on QGIS. For the difference between Manhattan Voronoi and "normal" Euclidean Voronoi, please check this link Can someone ...
5
votes
1answer
159 views

How to grow several concave hulls until they completely fill a larger area without overlap?

This is my problem: I have a very large point layer with polling station locations across one country; each point belongs to a specific constituency (900k points, 4k constituencies). I wish to use ...
0
votes
0answers
96 views

Grass 7 voronoi vertices error

I tried the voronoi diagram for area function and got the message "ERROR: Found 0 vertices" - any suggestion ?
0
votes
1answer
75 views

Graduated colouring Voronoi polygons? (QGis)

I've got a huge database of depth points for the whole Irish sea which I'd like to be a nice smooth surface, or at least have a depth value associated with the entire area (i.e. include the ...
3
votes
4answers
261 views

Can Voronoi/Thiessen polygons be created using ArcObjects without 3D Analyst license?

Has any body used ITinNodeCollection to generate Voronoi/Thiessen polygons. I have a point featureclass for which I want to create Voronoi/Thiessen polygons. Does this require 3d analyst license? I ...
4
votes
1answer
677 views

Obtain voronoi polygons which extend till the boundary of another polygon

I have certain hubs (coloured yellow) in a district (coloured light blue). I need to find polygons indicating the closest hub to every point in the district. The voronoi polygons that I obtained ...
0
votes
1answer
254 views

Offsetting Points by location

Sorry If you've read this before - I've tried to change the content so that it reflects what I need a little better. This question was marked as a duplicate although I read the the answer to the other ...
0
votes
0answers
593 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 ...
6
votes
1answer
325 views

How to find nearest neighbors of polylines?

I have a shapefile containing irregularly placed polylines (i.e., survey routes). Following the general idea of a paper I read, I would like to use tessellation to identify the neighbors for each ...
3
votes
0answers
158 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. ...
3
votes
3answers
459 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 ...
2
votes
1answer
381 views

Python Script that calls the Voronoi Polygons Function?

I've been looking to see if there was a way to call Voronoi Polygons function found in Vector/Geometry Tools, directly from the code but I have not found one. Does this currently exist? Is there a way ...
11
votes
5answers
4k 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 ...
6
votes
2answers
3k 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, ...
1
vote
3answers
809 views

Thiessen polygon input help

I am new to 10.0 and have never used the thiessen polygon tool -- i have a set of points and would like to create a thiessen polygon; what do i need to input (i.e. what type of input (.shp etc)?
7
votes
1answer
450 views

How to grid unevenly sampled categorical data?

I am looking for a method for gridding categorical data. I have extracted from nautical charts and field sheets a collection of points specifying the nature of the surface of the bottom of the ocean. ...
14
votes
1answer
2k 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 ...
4
votes
1answer
5k 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 ...
2
votes
0answers
306 views

Proximity Toolset Questions - Description, Examples of Usage, and Limitations

I was wondering if you could help me answer a few questions about the Proximity Toolset. I have been given the task of describing each tool in laymen terms, the typical usage of each tool, and most ...
8
votes
2answers
3k 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
7
votes
2answers
717 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?