Re: [gdal-dev] OSGeo.OGR.Geometry: Union the mutiple geometries at a time

Hi, I can't imagine any connection between Union and Convex/Concave hull. Union of the points in the example image is a MultiPoint geometry. The hull is a single geometry that encloses the input geometries, in this case it is a polygon. There is no need to consider hulls when doing Union.

Re: [gdal-dev] OSGeo.OGR.Geometry: Union the mutiple geometries at a time

I am referring to the below image - -- Sent from: http://osgeo-org.1560.x6.nabble.com/GDAL-Dev-f3742093.html ___ gdal-dev mailing list gdal-dev@lists.osgeo.org

Re: [gdal-dev] OSGeo.OGR.Geometry: Union the mutiple geometries at a time

Hi, Please explain what do you mean by "Concave Hull-based union geometry". Union is union as it is defined in the OpenGIS Simple Features Implementation Specification for SQL 1.1 standard. There is only one possible correct result from union. The source code is available if you are interested in

Re: [gdal-dev] OSGeo.OGR.Geometry: Union the mutiple geometries at a time

Thanks Even. Whether this algorithm internally use Convex Hull or Concave Hull? How to get Concave Hull-based union geometry using GDAL? Are these functionalities (ogr.CreateGeometryFromWkt..) available with C# bindings? Regards, Rajesh -- Sent from:

Re: [gdal-dev] OSGeo.OGR.Geometry: Union the mutiple geometries at a time

Rajesh, Use geom_collection.UnionCascaded() where geom_collection is a GeometryCollection / MultiPolygon of your many polygons. See https://github.com/OSGeo/gdal/blob/5fcc5dd5995af063065c253387bd9c767aeb8130/autotest/ogr/ogr_geos.py#L336 Even Le 18/03/2021 à 06:01, MRRAJESH a écrit :

[gdal-dev] OSGeo.OGR.Geometry: Union the mutiple geometries at a time

Developers, We came to know that OSGeo.OGR.Geometry is having the *Union *method which allows to the union of the two geometries (code snippet below). But this allows us one by one. How to union the multiple geometries (say 1000 geometries) at a time? Any methods or libraries in GDAL?