Questions tagged [convex-hull]

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

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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 ...
4
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1answer
574 views

Convex hull with n points using computational geometry libraries

I've been searching for a function to make the Convex Hull of a Spatial Object with N points, to make an spatial approximation with n-corners, as shown in the article "Comparison of Approximations of ...
1
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1answer
53 views

PostGIS- convert points to polygon based on multiple shared attributes

I have a PostgreSQL PostGIS point table (not multi-points). I want to convert the points to polygons (using convex-hull?) grouping the points by shared attributes from 2 columns. In this example, '...
1
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0answers
769 views

Detecting turns of route?

I'm doing a Python simulation of a vehicle, driving along a specified path. I generate dummy GPS readings, that fetch the current position of the vehicle, with some randomized error added. After a ...
5
votes
1answer
1k views

Growing several concave hulls until they completely fill larger area without overlap using QGIS? [closed]

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 ...
1
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0answers
17 views

Using convex hull for interpolation of individual plots or lump plots together in ArcMap?

This question is inspired by Using kriging to extrapolate values outside of sampling polygon in ArcMap? I'm working on a project trying to understand the lasting effects of historic scientific ...
2
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1answer
65 views

Knowing/converting AREA, PERIMETER units in QGIS?

I use Convexhull tool in QGIS and there are result value : AREA = 0.0017494390 PERIMETER = 0.1725495172 I thought the result was strange. So, I took a rough estimate of the points through the ...
0
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1answer
38 views

Minimum Bounding Geometry Convex Hull

I have 1000+ irregular shaped polygons where I would like to determine the orientation (azimuth) of their long axis. The polygons overlap in a few cases, if that matters. I am using the Minimum ...
1
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2answers
113 views

OpenJump LoCoH Analysis Output?

I really need some help! I am doing a k-LoCoH analysis in OpenJump. The analysis is working, but I'm having trouble understanding the output. There is a "density" column in the output, and I'm not ...
0
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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 ...
0
votes
1answer
159 views

Compute convex hull of points in a feature collection [closed]

I uploaded an asset (which was originally a shapefile of points) and imported it into my script as a feature collection. I would like to compute the convex hull of the points, but it seems this ...
2
votes
3answers
783 views

Is there a Cluster convex hull implementation in OpenLayers?

In this leaflet example. When hovered over a cluster marker, it shows the bounding area of the clustered features which is known as convex hull. Is there a way to reproduce it with OpenLayers?
2
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5answers
3k views

Creating Minimum Convex Polygon - Home Range from Points in QGIS

I just downloaded QGIS (3.0.2) and trying to create minimum convex polygon around points using minimum bounding geometry (convex hull). The videos and help documents I see online appear to be from ...
0
votes
0answers
91 views

Creating Polygon from groups of points

I have a point feature class (Address Points) and I am interested in creating a polygon feature class around groups of 500 address points. Is there a way I can do this programmatically, as opposed to ...
1
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2answers
89 views

Converting trajectory to outer edges polygon

Using PostGIS, I'm trying to solve the following problem: I have trajectory data (coordinates from API query), like on this image: and want to convert it into polygon, having only outer edges:
1
vote
1answer
398 views

Defining convex-hull of (clouds of) points using R? [closed]

I have multiple (clouds of) points, and would like to take the outer envelope of these points. This will allow me to polygonize my points. Using the convex-hull would help me, but in some cases, my ...
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 (...
2
votes
0answers
41 views

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 ...
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 ...
1
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1answer
297 views

How to create a convex hull in R based on the larger of two shapefiles' extents?

In R, I have two shapefiles: Shapefile A represents roads (polylines), Shapefile B some location (points). I want to plot the convex hull enclosing the study region, and it has to be set to the larger ...
2
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1answer
266 views

Convex hull area: what are the output units?

I have what I hope is a simple question. I'm doing convex hull calculations. What I have is area(convex_hull($geometry)). I get a number and that's all well and fine. Since I need to get a ratio of ...
2
votes
1answer
376 views

DBScan with Convexhull

I am new to GIS, I am using PostGIS(2.3). I have two problems I am not clear with Problem-1: I have list of locations(longitude, latitude, 4326), what is best/correct projection to use while ...
1
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0answers
19 views

Automatically digitize polygons by most outlying points within cluster in ArcMap [duplicate]

I'm looking for a tool or script that will allow me to automate the digitization of polygons by the most outlying points in a cluster of points with the same key attribute. Below is a sample image ...
1
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0answers
133 views

How to create view from ST_ConvexHull

I have a simple SpatiaLite DB containing one table with point features. I would like to generate a Minimum Convex Hull around that features. I could do that easily with one of the Convex Hull tools ...
0
votes
1answer
258 views

LoCoH or TLocoH home range estimators in ARC?

Is there a way to create a Getz and Willmers Local Convex Hull in ArcMap? The "Minimum Bounding Geometry" tool is insufficient for my purposes, as it greatly overestimates the sizes of home ranges. ...
1
vote
2answers
176 views

Create convex hull over DEM

I am trying to virtually put a blanket over a DEM so to say, in more technical terms, a convex hull over 3d point data. To get some insight in what I'm doing exactly, I will first explain my entire ...
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 ...
1
vote
1answer
104 views

Select tracks or part of tracks that are within a polygon?

I am studying a monkey species, I have GPS observation points which I used to make a convex polygon (Hull). I also have all of the survey trails imported and displayed in QGIS (See screen shot for ...
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 ...
2
votes
1answer
1k views

Creating polygons layer from point layer with conveks buffer

I have a point layer of >750000 points representing dwellings with district heating. Now, I want to create polygons for every n of points with a distance of n meters to the next point. I have a ...
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: ...
3
votes
1answer
156 views

qgis: generalisation & covex - how to? what plugin?

I'm looking for a way to generalize and simlify polygon to remove "internal spikes" as ilustrated below. The violet in input and green expected poligon.
1
vote
1answer
192 views

How do I draw the shortest imaginary boundary around a point dataset?

I would like to produce a range map for my species (smooth snakes in the south of England) using the IUCN-defined 'extent of occurrence' (EOO) as my metric. EOO is defined as 'the area contained ...
2
votes
1answer
444 views

Computing convex hull of table using PostGIS Query in MapServer?

I am basically trying to compute the convex hull of a table in postgresql but I can't seem to get the query correct. My ultimate goal is to use this query as a polygon layer. The columns in the table ...
1
vote
0answers
108 views

Finding boundary vertices from given set of coordinates? [duplicate]

How to find the the boundary co-ordinates from a given set of co-ordiantes? I understand that this question asked previously and answered here Finding boundary co-ordinates from given set of point ...
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 ...
2
votes
2answers
373 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 ...
2
votes
4answers
199 views

'Joining' polygons using PostGIS?

I'm looking for the best ways to 'group' a budge of block polygons in a new polygon that should be the town. My block layer is something like this: Or zoomed: And I'm looking to get something like ...
1
vote
0answers
253 views

Creating convex hull with geometry method of ArcPy? [closed]

I am trying to use the geometry method to calculate the convex hull around two polygons (polyA, polyB) with the following code: # Union both polygons to one (multipart) polygon: polyAB = polyA.union(...
6
votes
1answer
464 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 ...
0
votes
2answers
1k views

Openlayers 3: Draw Polygon (convex hull) around a cluster of points

I'm grouping a set of points as a cluster. Then I'm trying to draw a polygon around the points. Please see this link: Draw Poly I tried by sorting the points based on co-ordinates. But still I'm not ...
1
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1answer
386 views

QGIS generate convex hull for common attributes that have many values

If I have a points file where the points share common attributes, what's the best way to draw a convex hull around those common points using QGIS?
1
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0answers
29 views

Create polygons convex hull with arc basic [duplicate]

I have a bunch of polygons to make from points that need to be more precise than the min bounding box of closest rectangle or circle but don't have an advanced license. Does anybody have a workaround ...
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 ...
1
vote
2answers
212 views

Summarizing point data to multi point data and creating convex hull in R

I have latitude and longitude information like 26.847905 73.9575005 for about 800 points, I need to trim these lat/lon information to say 3 decimal places. I used the following syntax in R # ...
2
votes
0answers
123 views

Adapting a ConvexHull fonction to a ConcaveHull one

I have a database with over 150 000 points in a EPSG 2950 projection. As I wanted to cluster those points in polygons, I used a ConvexHull fonction. The goal was to create clusters where I would find ...
4
votes
1answer
469 views

Clustering (ConvexHull) data based on distance

First I would like to mention that I am not an expert with PostGreSQL so my question may seem dumb, but here it goes: I have a database with over 800 000 points associated to a geometry (EPSG 2950) ...
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, ...
5
votes
1answer
352 views

Packing polygons without intersection and empty places [closed]

How can I pack polygons without empty places and intersections? Please tell me everything that might help me (API, algorithms, etc.) I'm using: USPS API to get carrier routes. dbscan.js to ...
5
votes
1answer
3k views

Is there a QGIS equivalent to ArcGIS' Convex Hull and Circle under the Minimum Bounding Geometry tool?

I have the opportunity to run ArcGIS and QGIS side by side for a few months and was looking to see what comparisons there are. So I'm interested to know if there is a similar tool on QGIS?