[Gdal-dev] GEOS precision model?

[Howard Butler]

Ari,

I've had similar problems, and I think there's been other GEOS users  
with the same.  The options are quite limited however:
-- Make sure you are using the robust operations (see the C++ header  
files for details on what needs to be called) in the latest release  
candidate.  I don't think OGR uses these by default right now.
-- Tweak your precision models until you find something that works  
consistently and good enough.
-- Use a computational geometry library that does real math like CGAL  
or LEDA (I ended up taking this option).
-- Inject QD into GEOS to bump the precision up and at a likely cost  
in performance <http://crd.lbl.gov/~dhbailey/mpdist/>.  I don't know  
how challenging this would be, but I suspect others would be  
interested in it.

Howard

On Jun 26, 2007, at 11:18 AM, 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?
>
> Regards,
>
> Ari
>
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