[Gdal-dev] GEOS precision model?

[Frank Warmerdam]

Ari Jolma wrote:
> I'm doing some rather heavy duty geocomputation with OGR (via Perl 
> module Geo::OGR of course), mainly intersections. I run into a problem, 
> where GEOS throws a topology exception since the vertices of the two 
> geometries are very close to each other (6 digits same, then differences).
> 
> I'm no GEOS guru, but it seems there is a possibility to improve the 
> robustness of overlay operations with precision models(?). I think they 
> could be useful for me now.
> 
> Is there a way to take advantage of what GEOS offers (and what does it 
> really offer, if I could have a quick lesson...) via OGR? And if not, 
> would it be difficult to hack it in?

Ari,

OGR does not provide any access to the GEOS precision model.  In fact,
looking over the GEOS C API it does not either.  I think if you were
willing to do a custom build you would want to replace the following
in geos/capi/geos_c.cpp

static const GeometryFactory *geomFactory =
	GeometryFactory::getDefaultInstance();

with a customized geometry factory.  I don't know the details about
that though.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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