# Questions tagged [convex-hull]

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

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### 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, '...
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 ...
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### 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 ...
37 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 ...
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 ...
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 ...
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:
388 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 ...
158 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 ...
2k 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 ...
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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 ...
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 ...
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 ...
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 ...
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 ...
257 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. ...
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 ...
175 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 ...
397 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 ...
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### 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 ...
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.
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### 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 ...
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 ...
443 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 ...
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(...
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 ...
384 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?
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### 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 ...
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 ...
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### 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 # ...
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 ...
468 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) ...
351 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 ...
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?
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### 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 ...
615 views

### get the outline of a polygon

I have geojson data that draws shapes similar to the following: I wanted to know if there are any operations that can give me the geojson which represents the outline of these shapes represented by ...
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 ...
318 views

### Inflating the boundaries created with convex hull

I have a set of lan and lat points and have plotterd a convex hull for them using QGIS. A polygon is created along the set of points and plotting them on the MAP. Now I am trying to inflate the size ...
546 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 ...
107 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 ...
3k views

### Creating perimeter around multiple polygons using ArcGIS for Desktop?

This may have a simple answer that I'm just missing. I have multiple polygons in one shapefile I would like to make a larger Polygon around all of them. Is there a tool that is able to do this? ...
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: =&...
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### 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
1k views

### Postgis create polygon extent/convex hull from spatial table

Please help, I have a polygon layer representing building footprints. I want to create new view in postgis that will contain rectangle representing bounding box and also another view that will have ...
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### R - Occasional error when using alphahull package areaahull() function

I've recently started using the fantastic alphahull R package, which works beautifully most of the time but occasionally I am getting the following error when running the areaahull() function: Error ...
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### 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 ...
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 ...
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 ...