Smallest bounding geometry of an object or group of objects using concave angles. Also known as an alpha hull or shape.

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How to find the concave hull for a cloud of points in 3D space?

The existing algorithm for convex hull is not able to capture the feature for a set of 3D points. Moreover, I found few mathematic tools have this function to obtain the concave hull and their ...
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23 views

How to create polygon made from outside points of points shp? [duplicate]

I have DEM Data which is in SHP Format. After interpolating to raster, I need to clip the raster image. To do this, I need to transform the Point SHP into a Polygon SHP using only the outer-most ...
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1answer
73 views

QGIS equivalent to ArcGIS Aggregate Polygons?

I am looking for a tool in QGIS 2.40 that performs the function ArcGIS refers to as Aggregate Polygons. Basically it takes a group of polygons within a specified distance and creates a concave hull ...
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1answer
149 views

polygon from exterior points

How to convert points data to polygon, so as to form polygon from exterior point as shown above
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1answer
263 views

How to grow several concave hulls until they completely fill a larger area without overlap?

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 ...
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2answers
319 views

animate polygons in series of kml/geojson/shp

I have a series of KML files (though they could easily be converted to geoJSON, SHP, or anything else that ogr2ogr can handle), each file containing a set of polygons that correspond to the alpha ...
2
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1answer
421 views

Map projection lat, lon to pixel?

I'm trying to find the concave hull of a lat, lon pointset but when I project my points on my map it doesn't look like expected. I've tried a lineare projection and a spherical projection. My data is ...
3
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0answers
200 views

Hitting Memory Limits of PostGIS ST_ConcaveHull / Incomplete Shrink Wrap

I am trying to use PostGIS 2.0 on Postgres 8.4 to do some mapping. I am working with the NOAA Shapefiles, specifically their US States & Territories file located here: ...
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2answers
358 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 ...
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248 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 ...
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5answers
2k 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 ...
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15answers
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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 ...