[geos-devel] Unary Union (was: rgeos interface to R classes)

[Sandro Santilli]

On Fri, Feb 05, 2010 at 02:28:20PM +0100, Sandro Santilli wrote:
> On Fri, Feb 05, 2010 at 01:58:14PM +0100, Sandro Santilli wrote:
> > On Fri, Feb 5, 2010 at 12:29 PM, Roger Bivand <Roger.Bivand at nhh.no> wrote:
> 
> > > Seems to be in the 3.2.0/1.6.0 C API as GEOSUnionCascaded(), and works like
> > > the buffer trick for me (except for my unsolved scale problem).
> > 
> > I've checked the GEOS code. It's actually NOT the same classes being
> > used for CascadedUnion and UnaryUnion. Dunno about the actual
> > output characteristic, but it's surely documented (in JTS) to be different
> > from the buffer trick.
> 
> Oope, you were right. At least for polygons, it's the same
> of UnionCascaded.

... except postgis just returns the input geometry w/out even asking
GEOS to do anything with it (for single-geometry inputs) ...

--strk; 

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