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

[Roger Bivand]

On Fri, 5 Feb 2010, strk wrote:

> On Mon, Feb 01, 2010 at 09:48:57AM -0800, Martin Davis wrote:
>
>> The technique of using buffer(0) to union polygons is now deprecated in
>> favour of using Unary Union (Geometry.union() - not sure what the exact
>> GEOS signature is).  Unary Union is usually faster and more robust than
>> the previous technique.  You might want to check this out.
>
> Uhm, I might have missed this in my last port (either completely
> or just the outer interface). Is the JTS repository finally landed
> so to take a look ? I'm interested in evaluating its use for "geometry
> cleanup" purposes (http://trac.osgeo.org/postgis/ticket/399)

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).

Roger

>
> --strk;
>
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-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no