Questions tagged [convex-hull]

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

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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 ...
2
votes
2answers
877 views

Quick way to make a convex hull

I am using Python and ArcGIS 10.1. Is there a function or very quick way to extract points out of point feature class into an array without looping through a search cursor (as I have millions of ...
2
votes
2answers
370 views

Visualizing convex hull in QGIS?

There is no way to visualize a convexhull in qgis 1.8 lisboa? I have tried following views in Postgis 1.5 I was told to use an id column to publish it in Qgis. If you not use an id column, u cannot ...
3
votes
1answer
115 views

Extracting points bordering shape extent

I'm using ArcGIS 9.31. I have a set of points as elevation and in order to get a soft clip area for the TIN, I would like to extract only all the points bordering the extent of this shape, or to get ...
2
votes
2answers
667 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 ...
1
vote
0answers
655 views

How can I use Convex Hull to select an area with a space from the points?

This refer to this post : Read Here My goal is to select an area covering some points, but maintaining some space from points of border, like in the follow picture : I think ST_Convexhull will do ...
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 ...
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, ...
3
votes
1answer
284 views

Convex Hull in SAGA Gis

How does one go about creating a convex hull from a set of points in SAGA GIS? I read that this is possible in QGIS, but I prefer SAGA and would like to see if it is possible. Furthermore, if it is ...
5
votes
1answer
1k views

create convex hull polygons / cluster for sets of N points in a point dataset

I have 50k points in a feature class which I need to build convex hull or polygon for each set of 50 points that are nearby each other. I guess the question is very similar to create census areas for ...
4
votes
1answer
5k views

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

I've been trying to do some point analysis on some xyz data, I'm at the point where I've decided it is best to produce a boundary of my xyz files and put this with the metadata for each survey. Now ...
6
votes
1answer
460 views

convex hull over selected features

I am trying to achieve a convex hull over a feature Set returned by a query. But have been facing the error below which i am not able to figure out In order to debug to see how the convex hull works ...
67
votes
7answers
67k 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 ...
5
votes
2answers
789 views

Invalid Geometry Error after ST_ConvexHull

I've a Postgis table of around 80,000 points and want to be able to populate a second table summarizing the data with convex hulls based on points with a common attribute. For example, the data ...
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 ...
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 ...
115
votes
13answers
46k 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 (...
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: ...