# Questions tagged [delaunay]

A prefix to help define a type of mathematical transformation, such as Delaunay Triangulation, or Delaunay Tesselation

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### Creating constrained Delaunay triangulations for polygons

I have a set of polygons, some of them are connected, but most are not. Some of them are convex, some are not. Now I want to build a navigation mesh based on the polygons, and I find most of the ...
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1 vote
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### Why does ST_DelaunayTriangles return an empty GeometryCollection?

I'm currently struggling to calculate the area of a slightly non-planar surface in PostGIS. The area is a wall surface from a LOD2 data source. Here's an example: SELECT ST_AsText(ST_DelaunayTriangles(...
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### Calculating and visualizing interdistances among points in QGIS (Delauney Triangulation)

I have a point layer: and I would like to calculate and visualize interdistances among the points with lines automatically to see if there is any trend. The main issue is that if I connect all the ...
• 520
1 vote
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### TIN Interpolation in QGIS but with a predefined Delaunay triangulation

I have a set of points from which I am trying to perform a TIN triangulation. However, the algorithm for the triangulation (i.e. the resulting raster) creates triangles that I would like avoid for the ...
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### How to save a Delaunay triangulation in shapefile with Python?

I have a csv file with coordinates and values for each point. I have made a Delaunay Triangulation and I save it in .png and .pwg formats, but I also would to save in shapefile format, I try with ...
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### GDAL GRID Linear Interpolation Creating a Non Continuous Raster

I am using the GDAL GRID algorithm to create a raster from points using the Linear method. The points I have are generated from the river cross-section lines, and all have the same z value per line. I ...
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### Python implementation to generate Delaunay triangulation based spatial weight matrix [closed]

I'm looking for Python implementation for Delaunay triangulation based spatial weights. There are a lot of spatial weights techniques available in a Python geospatial library PySAL but Delaunay ...
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### Using GRASS v.delaunay with QGIS results with gaps in triangulation

When I use the GRASS v.delaunay algortithm in QGIS 3.18 on my dataset the output has gaps in it. But when I use the QGIS delaunay algorithm there are no problems and all is triangulated. The input ...
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### Making polygon layers always have area fields in QGIS

I am making Delaunay triangles of several (over 40) combinations of points and it is very tedious to output new shapefiles for each combination without even having the area of the triangles by default,...
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### Delaunay triangulation returning empty geometry in PyQGIS

I would like to compute the Delaunay Triangulation for polylines. But sometimes it works and sometimes it does not, I tried with hand drawn lines. lines=QgsProject.instance().mapLayersByName("...
1k views

### QGIS export to 3d mesh format

I'm testing qgis triangulation. So far I managed to extract a single polyogon, simplify it, and convert to points. The problem is that the triangulation produces something unexpected. This is the ...
710 views

### Creating a 3D TIN or similar 3D Delaunay triangulation in R

Background: I have topographical datasets with height information as a starting point. The endgame is to create a dataset of triangulations which I can use to import into Parasolid to be used further ...
398 views

### Calculating delaunay triangulation with two diagonal lines using ArcGIS Desktop?

How do I obtain a line output similar to a delaunay triangulation but with two diagonal lines, from a point layer containing a regular-spaced point grid using ArcGIS Desktop? The current result is ...
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1 vote
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### Arcs from a Delaunay Triagulation

I am trying to generate a Cost Distance table using Spatialite. I have several points in the table random_points for which I would like to compute the Delaunay triangulation and use the segments it ...
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### Incomplete Delaunay triangulation unsing pyqgis3

I'm writing a small Qgis3 python plugin to convert polygon shapefiles to input files for a scientific model. I therefore need to split up the polygon geometries to more simple geometries with up to 4 ...
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### Match SpatialPoints to Delaunay Triangles in R

I have 2 SpatialPointsDataFrame files. I compute the Delaunay Triangles from the first shapefile (shp1) as in the code below. Then I wish to assign each point from my second shapefile (shp2) to one of ...
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### Apollonius Graphs (Delaunay Graphs of Disks) in sfcgal or PostGIS?

I was wondering if there is support for Delaunay Graphs of Disks (a.k.a. Apollonius Graphs) in PostGIS/sfcgal? A CGAL function seems to exist for this. But I can't seem to find it in the PostGIS ...
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### Polygons hull QGIS [duplicate]

I'm currently working with old french cadastre on QGIS, I've vectorised it and now I want to tile it. I've georeferenced it, but it's not sufficient for a great result. To improve the result, I would ...
1k views

### Minimum wall-thickness of a non convex polygon with holes

What is the most efficient way to find the minimal wall-thickness (value and location) of a complex, non convex polygon area including holes? See example of a polygon in blue, with the minimum wall-...
2k views

### St_delaunaytriangles polygon with holes

I'm using PostGIS to decompose a polygon with a few holes into triangles via st_delaunaytriangles. Unfortunately, it does not return the right result with holes, because the triangles being outputted ...
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### 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 ...
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### Query Z at intersecting point locations from a MultiPolygonZ?

I create a MultiPolygonZ geometry with ST_DelaunayTriangles(). select st_setsrid( ST_CollectionExtract( ST_DelaunayTriangles( ST_GeomFromText('MULTIPOINT ...
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1 vote
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### Constrained Delaunay Triangulations in PostGIS?

It is possible to make Constrained Delaunay triangulations in PostGIS (PostgreSQL)? I have a Polygon and I need to make internal triangulation like this: I tried to use ST_DelaunayTriangles but is ...
• 61
1 vote
982 views

### How to Create Voronoi Polygon Diagram within surrounding polygon?

I want to create a Voronoi Diagram within an outer polygon. I want to retrieve a result very similar to this solution, which uses ST_DelaunayTriangles() to create Triangles. Actually, it would ...
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### Calculating a new attribute for a polygon based on its corners

i have a pointlayer with a real number as attribute named amount. I want to calculate and visualize the difference of amount between neighbourhood points. So first I made a delaunay triangulation ...
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### How do I create line vectors with a new ID from points in QGIS?

I have a list of stations from which I would like to create a network of lines (the one created with the Delaunay triangulation would be fine) identified by a particular ID (for example, "AB" for the ...
2k views

### How to set up a threshold for Delaunay triangulation?

I've been working Delaunay triangulation on a set of random points inside a group of mostly linear areas (in fact, buffers around rivers). The problem is that while the triangulation works correctly ...
• 399
1 vote
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### Delaunay Triangulation on labeled data

I have a table with locations and labeled data and I need to apply Delaunay Triangulation on specific labeled rows. For example, I have some locations labeled as schools, hostels, gardens, ... and I ...
• 53
1 vote
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### Extracting coordinates of a triangulation from DEM data

I'm working on the succinct representation of planar graphs and now I'm trying to obtain some datasets to test my results. I saw that Delaunay triangulations of elevation data can be a good source of ...
1 vote
146 views

### How to identify Sliver triangles in a TIN surface and count them? [closed]

Is it possible to count slivers in a TIN? I generated a Delaunay triangulation surface model and i want to know how many slivers the TIN has.
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