Questions tagged [convex-hull]

Smallest bounding area for an object or group of objects with no concave angles.

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116
votes
13answers
47k views

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

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 (...
69
votes
7answers
68k views

Finding minimum-area-rectangle for given points?

As you see in the figure, the question is: How to find the minimum-area-rectangle (MAR) fitted on the given points? and a supporting question is: Is there any analytical solution for the ...
14
votes
8answers
20k views

Creating convex hull in ArcGIS Desktop?

I would like to be able to create a convex hull in ArcGIS Desktop 9.x, but I cannot find an appropriate tool. How does one go about creating one? I am interested in answers for all license levels: ...
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, ...
18
votes
6answers
26k views

Finding boundary co-ordinates from given set of point co-ordinates?

Given a set of coordinates, How do we find the boundary coordinates. <== Figure 1 Given the coordinates in the above set, How can I get the coordinates on the red boundary. Boundary is the polygon ...
8
votes
5answers
4k views

Algorithm to find polygons enclosing points

I'm trying to find an algorithm that can determine the smallest possible polygons to cover a number of points. I know how to get the convex hull around all the points, but say that the points are ...
13
votes
2answers
1k views

How to build a minimum convex hull crossing the 180 degrees line?

I've been building convex hulls for species that inhabit the Indo-Pacific (~ from 20 to -65 degrees of longitude). The problem I've encountered is that for the species that can be found on both sides ...
2
votes
2answers
672 views

Is it possible to get the points used for the convex hull in osm2po?

I have a non-convex hull algorithm that I want to use for an app. With OSM2PO, it's possible to get a convexHull, but is there a way to get the points before the hull is constructed? More, it would ...
2
votes
1answer
151 views

Make convex hulls opaque or transparent

I have a series of convex hulls that I want to overlay but I want to be able to see all of them at the same time. How do I do this so? I'm guessing making them slightly transparent will do the trick
1
vote
2answers
155 views

Creating a large amount of convex polygons using existing coordinates

I downloaded the georeferenced event dataset (top left) from this website: http://ucdp.uu.se/downloads/ It consists of coordinates of violent conflicts which differ in time and space. My aim is to ...
7
votes
3answers
2k views

inner convex-hulls in a set of 2D points

A set of 2D Points are scattered randomly (i.e., no specified pattern), we are interested in finding all inner-convex-hulls (ICH) in an order of largest in area to a minimum until the entire study ...
3
votes
1answer
278 views

PostGIS ST_ConvexHull for cube corners not as expected

I'm new to PostGIS and am wondering whether ST_ConvexHull will be of use in a particular work problem. Trying out some simple cases to make sure I understand what it's doing, I didn't expect this: =&...
3
votes
1answer
549 views

Convex Hull operation not specific enough

I have yield data as point values, and I simply want to create the boundary around this layer. I have used the Minimum Bounding Geometry tool and selected Convex Hull to do this, however it maintains ...
0
votes
0answers
398 views

Looking for a US state file for geofences with as few geofences per state as possible (so group islands with mainland)

UPDATED TO MUCH MORE DETAILED QUESTION I'm building a set of geofences to be installed on a GPS unit to track vehicles as they cross state lines. The list of geofences are simple latitude/longitude ...
0
votes
0answers
23 views

GRASS v.hull for many point sets

I have map "my_pointmap" with 3D points with ids=(1,2,3...N). I have also list of subsets of these point ids , S = [(1,2,3,4),(2,4,10,12), ...]. I would love to get GRASS GIS vector map with |S| 3D ...