Questions tagged [convex-hull]

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

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77
votes
7answers
80k 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 ...
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1answer
39 views

ST_ConvexHull excludes some points

I'm trying to create convex hull for about 25000 points stored in the table. ST_ConvexHull run successfully, but resulting geometry does not covers some points. What could be a reason? And it is not ...
0
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0answers
43 views

DBSCAN and CONVEXHULL: how to obtain coordinates of the convexhull polygons

Iam using DBSCAN to cluster coordinates together and then using convexhull to draw 'polygons' around each cluster. I then want to extract the coordinates of the convex hull objects however the code im ...
3
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1answer
165 views

Computing convex hull of points using shapely

I have a points shapefile and I want to compute the convex hull of the points using shapely, and output the result as a shapefile using Fiona. Does anyone know how I can do that? This is what I have ...
122
votes
13answers
50k 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 (...
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1answer
152 views

Convex Hull in GeoPandas

I have a shapefile with a number of points. Using GeoPandas, I am trying to create a convex hull around the set of points. However, my output layer returns the same points as were fed in. My ...
3
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0answers
92 views

Creating convex hull by expression by aggregating points

I would like to recieve the centroid of a convex hull of a group of points in a layer, grouped by its name. This needs to be done by expressions, available in QGIS 3.4. E.g. I have this list of points:...
3
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1answer
229 views

Creating convex hull of set of points using QGIS

I have a shapefile layer with a set of points. I would like to enclose them (or turn them) into the polygon (with the line in the middle). I tried this: Converting cluster of Points to Polygons ...
0
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0answers
11 views

Converting point to polygon based on attribute value using ArcMap [duplicate]

I have survey points with a attribute "settlement name" and I need to create polygons from point with same settlement name. The polygon should enclose all the points with same settlement name. Any ...
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2answers
923 views

Getting outline of polygon as GeoJSON?

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 ...
2
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1answer
65 views

Selecting random points from specific attribute in yield map using QGIS

I am using QGIS. A farmer has sent me the shapefiles from his John Deere combine. They were three shapefiles that I have merged into one layer. The shapefile is from one field with a treated ...
4
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6answers
5k 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
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0answers
40 views

Convex Hull not outputting expected number of features

I have a .csv file with observations of various species and I want a polygon to illustrate the area where those species occur. I ran the Convex Hull, grouped by the species' names field, which ...
2
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1answer
338 views

Creating minimum bounding geometry using the convex hull method in R

I would like to create a small enveloppe around a set of polygons that encloses around them. I would like to avoid using the bounding box function (example below) because it would be too big. Rather, ...
4
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1answer
641 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
231 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
847 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 ...
6
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
36 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
99 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
53 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
124 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
41 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
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1answer
217 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
842 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?
0
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0answers
150 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
104 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
843 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 ...
2
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0answers
45 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
440 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
votes
1answer
305 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
462 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
167 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
298 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
210 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
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0answers
483 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
121 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
592 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 ...
15
votes
8answers
21k 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
161 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
211 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
685 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
155 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 ...
19
votes
6answers
30k 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
402 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
204 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
288 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(...