[postgis-devel] Snap-Rounding based overlay operations

[Sandro Santilli]

Martin Davis has a plan to add in JTS support for a new
algorithm to provide a fully robust overlay operation.

The algorithm is based on using a reference grid to snap
existing and newly-found vertices, so first step of the
algorithm would be converting the input geometries to
a FIXED precision model, if needed.

Here's previous mention of this plan:
https://trac.osgeo.org/postgis/wiki/ToleranceDiscussion#Snaprounding

My understanding (Martin please correct me if I'm wrong) is that
the goal of the new SnapRounding algorithm is for it to become
the standard one for conducting operations against FIXED precision
geometries, but a period of broader testing is desired.

My idea to expose such new algorithm on the PostGIS side
is to add a new optional parameter to the overlay
operations to represent the requested precision, and have
such parameter trigger engaging the new SnapRounding algorithm.

An alternative solution suggested by Martin was to use a GUC to
enable the new GEOS algorithm (and then I guess the operation
precision too).

Opinions/preferences/questions ?

--strk;