Discrete Hausdorff distance implementation (through GEOS)

[vincentp]

JTS and GEOS have a discrete Hausdorff distance algorithm. It is currently not exposed in GEOS C API, nor in PostGIS. A patch for GEOS is available to expose these functions : ​http://trac.osgeo.org/geos/ticket/264

Please find attached a patch to PostGIS trunk (at rev 4206) that implements Hausdorff distance calculation using the GEOS C API provided by this patch :

ST_HausdorffDistance(geometry, geometry) and its variant with segment densification ST_HausdorffDistance(geometry, geometry, float)

Documentation (from JTS) and unit test are included.

As the GEOS patch has still not been commited, you'll have to patch and recompile geos to test it. The GEOS version test in postgis.sql.in.c are made on GEOS 31 so as to be able to test. It should be changed to the GEOS version patch #264 will be commited to.

This is my first patch for PostGIS, please be indulgent I'll be waiting for a review to fix or improve the patch so that it can be commited.

[pramsey]

I find this line in the patch confusing

#if POSTGIS_GEOS_VERSION >= 31 
-- Requires GEOS >= 3.2.0 

Your comment correctly indicates your GEOS requirement, but your macro test does not. I think you'll want to fix all those macro tests.

[vincentp]

Hausdorff distance in postgis (with right geos version check)

[pramsey]

Applied to trunk at r4208.

[pramsey]

And thanks! Good first contribution. Documented, tests included, you put me to shame.