Index: postgis/lwgeom_geos.c
===================================================================
--- postgis/lwgeom_geos.c (revision 4206)
+++ postgis/lwgeom_geos.c (working copy)
@@ -62,6 +62,8 @@
*/
Datum linemerge(PG_FUNCTION_ARGS);
Datum coveredby(PG_FUNCTION_ARGS);
+Datum hausdorffdistance(PG_FUNCTION_ARGS);
+Datum hausdorffdistancedensify(PG_FUNCTION_ARGS);
Datum pgis_union_geometry_array_old(PG_FUNCTION_ARGS);
Datum pgis_union_geometry_array(PG_FUNCTION_ARGS);
@@ -91,6 +93,91 @@
}
/**
+ * @brief Compute the Hausdorff distance thanks to the corresponding GEOS function
+ * @example hausdorffdistance {@link #hausdorffdistance} - SELECT st_hausdorffdistance(
+ * 'POLYGON((0 0, 0 2, 1 2, 2 2, 2 0, 0 0))'::geometry,
+ * 'POLYGON((0.5 0.5, 0.5 2.5, 1.5 2.5, 2.5 2.5, 2.5 0.5, 0.5 0.5))'::geometry);
+ */
+
+PG_FUNCTION_INFO_V1(hausdorffdistance);
+Datum hausdorffdistance(PG_FUNCTION_ARGS)
+{
+ PG_LWGEOM *geom1;
+ PG_LWGEOM *geom2;
+ GEOSGeometry *g1;
+ GEOSGeometry *g2;
+ double result;
+ int retcode;
+
+ POSTGIS_DEBUG(2, "hausdorff_distance called");
+
+ geom1 = (PG_LWGEOM *) PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
+ geom2 = (PG_LWGEOM *) PG_DETOAST_DATUM(PG_GETARG_DATUM(1));
+
+ initGEOS(lwnotice, lwnotice);
+
+ g1 = (GEOSGeometry *)POSTGIS2GEOS(geom1);
+ g2 = (GEOSGeometry *)POSTGIS2GEOS(geom2);
+ retcode = GEOSHausdorffDistance(g1, g2, &result);
+ GEOSGeom_destroy(g1);
+ GEOSGeom_destroy(g2);
+
+ if (retcode == 0)
+ {
+ elog(ERROR,"GEOS HausdorffDistance() threw an error!");
+ PG_RETURN_NULL(); /*never get here */
+ }
+
+ PG_FREE_IF_COPY(geom1, 0);
+ PG_FREE_IF_COPY(geom2, 0);
+
+ PG_RETURN_FLOAT8(result);
+}
+
+/**
+ * @brief Compute the Hausdorff distance with densification thanks to the corresponding GEOS function
+ * @example hausdorffdistancedensify {@link #hausdorffdistancedensify} - SELECT st_hausdorffdistancedensify(
+ * 'POLYGON((0 0, 0 2, 1 2, 2 2, 2 0, 0 0))'::geometry,
+ * 'POLYGON((0.5 0.5, 0.5 2.5, 1.5 2.5, 2.5 2.5, 2.5 0.5, 0.5 0.5))'::geometry, 0.5);
+ */
+
+PG_FUNCTION_INFO_V1(hausdorffdistancedensify);
+Datum hausdorffdistancedensify(PG_FUNCTION_ARGS)
+{
+ PG_LWGEOM *geom1;
+ PG_LWGEOM *geom2;
+ GEOSGeometry *g1;
+ GEOSGeometry *g2;
+ double densifyFrac;
+ double result;
+ int retcode;
+
+
+ geom1 = (PG_LWGEOM *) PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
+ geom2 = (PG_LWGEOM *) PG_DETOAST_DATUM(PG_GETARG_DATUM(1));
+ densifyFrac = *(double *) PG_DETOAST_DATUM(PG_GETARG_DATUM(2));
+
+ initGEOS(lwnotice, lwnotice);
+
+ g1 = (GEOSGeometry *)POSTGIS2GEOS(geom1);
+ g2 = (GEOSGeometry *)POSTGIS2GEOS(geom2);
+ retcode = GEOSHausdorffDistanceDensify(g1, g2, densifyFrac, &result);
+ GEOSGeom_destroy(g1);
+ GEOSGeom_destroy(g2);
+
+ if (retcode == 0)
+ {
+ elog(ERROR,"GEOS HausdorffDistanceDensify() threw an error!");
+ PG_RETURN_NULL(); /*never get here */
+ }
+
+ PG_FREE_IF_COPY(geom1, 0);
+ PG_FREE_IF_COPY(geom2, 0);
+
+ PG_RETURN_FLOAT8(result);
+}
+
+/**
* @brief This is the final function for GeomUnion
* aggregate. Will have as input an array of Geometries.
* Will iteratively call GEOSUnion on the GEOS-converted
Index: postgis/uninstall_postgis.sql.in.c
===================================================================
--- postgis/uninstall_postgis.sql.in.c (revision 4206)
+++ postgis/uninstall_postgis.sql.in.c (working copy)
@@ -397,6 +397,12 @@
DROP FUNCTION buffer(geometry,float8);
DROP FUNCTION ST_Intersection(geometry,geometry);
DROP FUNCTION intersection(geometry,geometry);
+#if POSTGIS_GEOS_VERSION >= 32
+DROP FUNCTION ST_HausdorffDistance(geometry, geometry)
+#endif
+#if POSTGIS_GEOS_VERSION >= 32
+DROP FUNCTION ST_HausdorffDistance(geometry, geometry, float8)
+#endif
---------------------------------------------------------------
Index: postgis/postgis.sql.in.c
===================================================================
--- postgis/postgis.sql.in.c (revision 4206)
+++ postgis/postgis.sql.in.c (working copy)
@@ -3918,6 +3918,24 @@
LANGUAGE 'C' IMMUTABLE STRICT;
#endif
+#if POSTGIS_GEOS_VERSION >= 32
+-- Requires GEOS >= 3.2.0
+-- Availability: 1.5.0
+CREATE OR REPLACE FUNCTION ST_HausdorffDistance(geometry, geometry)
+ RETURNS FLOAT8
+ AS 'MODULE_PATHNAME', 'hausdorffdistance'
+ LANGUAGE 'C' IMMUTABLE STRICT;
+#endif
+
+#if POSTGIS_GEOS_VERSION >= 32
+-- Requires GEOS >= 3.2.0
+-- Availability: 1.5.0
+CREATE OR REPLACE FUNCTION ST_HausdorffDistance(geometry, geometry, float8)
+ RETURNS FLOAT8
+ AS 'MODULE_PATHNAME', 'hausdorffdistancedensify'
+ LANGUAGE 'C' IMMUTABLE STRICT;
+#endif
+
-- Deprecation in 1.2.3
CREATE OR REPLACE FUNCTION difference(geometry,geometry)
RETURNS geometry
Index: doc/reference.xml
===================================================================
--- doc/reference.xml (revision 4206)
+++ doc/reference.xml (working copy)
@@ -9818,6 +9818,83 @@
+
+
+ ST_HausdorffDistance
+
+ Returns the Hausdorff distance between two geometries.
+
+
+
+
+
+ float ST_HausdorffDistance
+
+ geometry
+ g1
+
+ geometry
+ g2
+
+
+ float ST_HausdorffDistance
+
+ geometry
+ g1
+
+ geometry
+ g2
+
+ float
+ densifyFrac
+
+
+
+
+
+ Description
+
+ Implements algorithm for computing a distance metric which can be thought of as the "Discrete Hausdorff Distance".
+This is the Hausdorff distance restricted to discrete points for one of the geometries.
+
+When densifyFrac is specified, this function performs a segment densification before computing the discrete hausdorff distance. The densifyFrac parameter sets the fraction by which to densify each segment. Each segment will be split into a number of equal-length subsegments, whose fraction of the total length is closest to the given fraction.
+
+
+
+
+The current implementation supports only vertices as the discrete locations. This could be extended to allow an arbitrary density of points to be used.
+
+
+
+
+ This algorithm is NOT equivalent to the standard Hausdorff distance. However, it computes an approximation that is correct for a large subset of useful cases.
+ One important part of this subset is Linestrings that are roughly parallel to each other, and roughly equal in length. This is a useful metric for line matching.
+
+
+
+
+
+
+ Examples
+
+ postgis=# SELECT st_HausdorffDistance(
+ 'LINESTRING (0 0, 2 0)'::geometry,
+ 'MULTIPOINT (0 1, 1 0, 2 1)'::geometry);
+ st_hausdorffdistance
+ ----------------------
+ 1
+(1 row)
+
+ postgis=# SELECT st_hausdorffdistance('LINESTRING (130 0, 0 0, 0 150)'::geometry, 'LINESTRING (10 10, 10 150, 130 10)'::geometry, 0.5);
+ st_hausdorffdistance
+ ----------------------
+ 70
+(1 row)
+
+
+
+
+
ST_Distance_Sphere
Index: regress/Makefile.in
===================================================================
--- regress/Makefile.in (revision 4206)
+++ regress/Makefile.in (working copy)
@@ -52,7 +52,8 @@
kml \
regress_ogc \
regress_bdpoly \
- regress_proj
+ regress_proj \
+ hausdorff
# Covers/CoveredBy only if GEOS >= 3.0
ifeq ($(shell expr $(POSTGIS_GEOS_VERSION) ">=" 30),1)
Index: regress/hausdorff_expected
===================================================================
--- regress/hausdorff_expected (revision 0)
+++ regress/hausdorff_expected (revision 0)
@@ -0,0 +1,6 @@
+hausdorff_poly_poly|0.707106781186548
+hausdorff_ls_ls|1
+hausdorff_ls_ls_2|2
+hausdorff_ls_mp|1
+hausdorff_ls_ls_3|14.142135623731
+hausdorffdensify_ls_ls|70
Index: regress/hausdorff.sql
===================================================================
--- regress/hausdorff.sql (revision 0)
+++ regress/hausdorff.sql (revision 0)
@@ -0,0 +1,37 @@
+-- tests for Hausdorff distances
+
+-- polygon and polygon
+SELECT 'hausdorff_poly_poly', st_hausdorffdistance(
+ 'POLYGON((0 0, 0 2, 1 2, 2 2, 2 0, 0 0))'::geometry,
+ 'POLYGON((0.5 0.5, 0.5 2.5, 1.5 2.5, 2.5 2.5, 2.5 0.5, 0.5 0.5))'::geometry);
+-- 0.707106781186548
+
+-- linestring and linestring
+SELECT 'hausdorff_ls_ls', st_hausdorffdistance(
+ 'LINESTRING (0 0, 2 1)'::geometry
+ , 'LINESTRING (0 0, 2 0)'::geometry);
+-- 1.0
+
+-- other linestrings
+SELECT 'hausdorff_ls_ls_2', st_hausdorffdistance(
+ 'LINESTRING (0 0, 2 0)'::geometry,
+ 'LINESTRING (0 1, 1 2, 2 1)'::geometry);
+-- 2.0
+
+-- linestring and multipoint
+SELECT 'hausdorff_ls_mp', st_hausdorffdistance(
+ 'LINESTRING (0 0, 2 0)'::geometry,
+ 'MULTIPOINT (0 1, 1 0, 2 1)'::geometry);
+-- 1.0
+
+-- another linestring and linestring
+SELECT 'hausdorff_ls_ls_3', st_hausdorffdistance(
+ 'LINESTRING (130 0, 0 0, 0 150)'::geometry,
+ 'LINESTRING (10 10, 10 150, 130 10)'::geometry);
+-- 14.142135623730951
+
+-- hausdorf with densification
+SELECT 'hausdorffdensify_ls_ls', st_hausdorffdistance(
+ 'LINESTRING (130 0, 0 0, 0 150)'::geometry
+ , 'LINESTRING (10 10, 10 150, 130 10)'::geometry, 0.5);
+-- 70.0