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Results for "concave hull" "convex hull"
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144 votes
14 answers
79k views

What are Definition, Algorithms and Practical Solutions for Concave Hull?

Convex Hull A convex hull of a shape is defined as: In mathematics, the convex hull or convex envelope for a set of points X in a real vector space V is the minimal convex set containing X (Wikipedia) … Concave Hull A concave hull is visualized using the red line in the image below (the blue line visualizes the convex hull). …
Adam Matan's user avatar
  • 6,878
10 votes
1 answer
7k views

C# implementation of concave hull / alpha shapes [closed]

I'm looking for a C# implementation of the Concave hull (alpha shapes) algorithm. I already found several Java, Python and C++ implementation but no C# version. … This will produce a convex hull, which I don't need. Something like this is what I need: http://www.geosensor.net/phpws/index.php? …
Paul Meems's user avatar
4 votes
3 answers
16k views

How to find the concave hull for a cloud of points in 3D space?

The existing algorithm for convex hull is not able to capture the feature for a set of 3D points. … Moreover, I found few mathematic tools have this function to obtain the concave hull and their responding points. Given the data of spheres: x1 y1 z1 radii_1 x2 y2 z2 radii_2 ... …
KOF's user avatar
  • 141
7 votes
0 answers
187 views

How to change the Point Cluster circle symbol to a convex hull

I would like to build an expression applied to a circle symbol that substitutes the circle symbol for the convex hull or concave hull geometry that operates with the Point Cluster render algorithm used … Here is a simulation screenshot of what I am looking for: The goal would be to use the Geometry Generator to change the circle symbol for a convex hull geometry that visualizes the grouped points inside …
Ingrid Ingravida's user avatar
1 vote
0 answers
366 views

Simplify Polygon - no loss allowed, looking for a concave hull - ArcMap

hull polygon, but that follows the edges into the convex areas. … So, before I jump into the rabithole fully, is there a way to produce a concave hull efficiently within ArcMap / ArcPy? …
Kristian Herner's user avatar
1 vote

Making Outside Buffer in QGIS?

The screenshot shows the concave hull in red over the convex hull in purple. There are still a few yellow lines within the concave hull, but it is much better than the convex hull. …
Jim O'Leary's user avatar
4 votes
1 answer
7k views

Best way to get Convex Hull/Boundary of millions of points

Now the part im stuck on is I've got over 15,000 surveys to compute the boundary of, tried convex hull and concave hull with varying results. …
Jamo's user avatar
  • 1,457
10 votes

QGIS equivalent to ArcGIS Aggregate Polygons?

While the creation of a convex-hull is a pretty straightforward operation, because there is only one possible convex-hull for a given set, this is not true in the case of the concave-hull. … Santos (2007): Concave Hull: A k-nearest neighbors approach for the computation of the region occupied by a set of points Other open-source GIS implementations of convex-hull computations are available …
skualos's user avatar
  • 173
10 votes
Accepted

Smoothing round border of created buffer in QGIS

This is a case for a convex or concave hull - depending how much additional space you want to include. … Concave hull gives you more flexibility: there is just one single convex hull per geometry, but different possible concave hulls (depending on input paramenters). …
Babel's user avatar
  • 74.9k
6 votes

Filling gaps between polygons using QGIS

Wouldn't you want a concave hull? A convex hull will give you a large amount of area that isn't part of the block. For example, a convex hull would fill in that big gap in the "hook" park of block 1. …
wild_ecology's user avatar
9 votes

What are Definition, Algorithms and Practical Solutions for Concave Hull?

QGIS does have Concave hull algorithm. … Parameters Input point layer [vector: point] put parameter description here Threshold (0-1, where 1 is equivalent with Convex Hull) [number] put parameter description here Default: 0.3 Allow holes …
whyzar's user avatar
  • 12.1k
6 votes

How to find the concave hull for a cloud of points in 3D space?

A convex hull is unique, whereas there are many possible concave hulls. So you cannot say "the concave hull" but "a concave hull". … There is possibly a minimal volume concave hull, but this is not the case on the example you shown. …
galinette's user avatar
  • 161
1 vote

Simplifying polygon edge while preserving minimum area and width

There are at least two possibilities: convex and concave hull. This is not software specific, both kind of hulls can be created with different software packages. … Concave hull: Menu Processing / Toolbox / Concave hull (k-nearest neighbor). …
Babel's user avatar
  • 74.9k
3 votes
Accepted

Creating polygon around set of points using PyQGIS

Using the "Concave hull (alpha shapes)" geoalgorithm. … hull) to 1 (convex hull)) should be done. …
Taras's user avatar
  • 34k
9 votes
Accepted

Algorithm to find polygons enclosing points

K-means clustering) first, followed by a hull (convex hull, but a concave hull may have a smaller area but more difficult to implement). …
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