[gdal-dev] Calculate footprints of shapefiles

[Armin Burger]

Chaitanya

thanks for the hints. So a sort of Union operation seems to be necessary. I need to check how fast that is with OGR on larger shapefiles (I want to store in PostGIS just the footprint, not the full geometry collection). The ConvexHull could be a good alternative to a simplified boundary. 

I understand how the normal Union() works, it merges 2 geometries into a new one. But I don't get it what UnionCascade() is doing. It applies a Union on a single geometry and returns the new geometry, what is it actually unioning/merging then? 

Regards, 
Armin


-------- Original-Nachricht --------
> Datum: Wed, 16 Mar 2011 10:06:57 +0530
> Von: Chaitanya kumar CH <chaitanya.ch at gmail.com>
> An: armin.burger at gmx.net
> CC: Marius Jigmond <mariusjigmond at hotmail.com>, gdal-dev at lists.osgeo.org
> Betreff: Re: [gdal-dev] Calculate footprints of shapefiles

> Armin,
> 
> This can be done in either OGR or PostGIS.
> 
> For OGR, refer to the OGRGeometry class reference, especially the
> ConvexHull(), Union() and UnionCascaded() functions.
> For PostGIS, ST_Boundary() and ST_Union().
> 


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