[geos-devel] Precision/tolerance questions

[Hugo Mercier (ML)]

Hi all,

I am not very familiar with the way GEOS can handle precision models ...

If I am correct, having a "fixed" precision model, i.e. a regular grid
allows to define a tolerance where (point) coordinates will be snapped
before computations.
Does it mean also predicates work with a tolerance, like the
intersection test between a point and a line will take a distance into
account ?

Similarly on this page
https://trac.osgeo.org/postgis/wiki/ToleranceDiscussion

I can read "Adding a PrecisionModel to the GEOS functionality uses a
precision grid to "snap" all coordinates, which could eliminate some
rounding and robustness issues with some functions. "
What rounding and robustness issues are they ? and which functions ?

Thanks