[geos-devel] Exposing Precision model through C-API

Anubhav Jaiswal anubhav2503 at gmail.com
Thu Feb 13 03:55:17 PST 2014


Just wanted to know whether GEOS is applying for GSoC'14 under OSGeo. If
yes, will this(exposing precision model) be a sufficient task or are there
any other project ideas for GSoC.


On Thu, Feb 13, 2014 at 2:24 PM, Rémi Cura <remi.cura at gmail.com> wrote:

> I'm Captain obvious here,
> but maybe you should take a look at CGAL, which is the reference lib
> regarding to precision issue. (I'm not speaking of the exact kernel.)
> Also Geos is a port of JTS, but I don't know if everything was ported
> (like this?
> http://tsusiatsoftware.net/jts/javadoc/com/vividsolutions/jts/geom/PrecisionModel.html
> ).
> All in all, exposing precision model is not a design or interface problem,
> but an algorithmic problem with no solution (except going the exact
> precision way), thus it is a matter of compromises and balance, because
> precise output cannot be guaranteed (if you chain operations like
> buffer(buffer(...buffer(geom)...)), enforcing precision is very difficult ).
> Maybe people from SFCGAL project would have a lot to say, because they
> must have done something about precision issue when writting/reading to
> Cheers,
> Rémi-C
> 2014-02-12 17:52 GMT+01:00 Sandro Santilli <strk at keybit.net>:
> On Wed, Feb 12, 2014 at 10:08:07PM +0530, Anubhav Jaiswal wrote:
>> > Hi,
>> >
>> > Can someone point me to any other geometric model which has already been
>> > exposed through C-API. It will make it easier for me to implement for
>> > Precision Model.
>> The C-API completely hides the PrecisionModel to the client
>> and internally forces Floating, by using the default
>> GeometryFactory (geos_ts_c.cpp:209)
>> In order to use a different PrecisionModel you'll need
>> to construct a different GeometryFactory using that model,
>> and the constructed GeometryFactory will need to stay alive
>> for the whole lifetime of any geometry that's been constructed
>> with that factory.
>> --strk;
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*Anubhav Jaiswal*

*B. Tech + MS by Research*

*Lab for Spatial Informatics,*

*Computer Science and Engineering,*

*IIIT Hyderabad *
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