Hi all,
JASPA has a ST_SNAP function using JTS function. I guess with GEOS
should be similar.
You can snap the segments and vertex of a geometry to the vertex of
anotther one.
http://jaspa.forge.osor.eu/ST_Snap.html
Anyways, in my opinion this algorithm should be modified a little bit to
use in a spatial database using real cartography.
Some interesting comments from Martin Davis to my question in the jts list.
http://sourceforge.net/mailarchive/forum.php?thread_name=4C534B34.5090003%40cgf.upv.es&forum_name=jts-topo-suite-user
In JASPA 0.2 (maybe around march) a new system with topology rules and I
think a tolerance system will be introduced.
Hope it helps,
Jose
public static Geometry ST_Snap(Geometry geom0, Geometry geom1, double
tolerance) throws JASPAJTSException, JASPAGeomMismatchException {
if (GeomProperties.errorIfDifferentSRIDorCoorDim (geom0,
geom1)) return null;
GeometrySnapper snapper = new GeometrySnapper(geom0);
Geometry res = null;
try {
res = snapper.snapTo(geom1, tolerance);
/*
Geometry[] snapped = GeometrySnapper.snap(geom0, geom1,
tolerance);
if (snapped == null || snapped.length < 2) return null;
Geometry res = snapped[0];
*/
} catch (RuntimeException e) {
//Catch the runtime JTS Exceptions
Core.manageJTSExceptions(e);
}
return res;
}
El 16/11/2010 13:04, Jan Hartmann escribió:
On 11/15/10 18:03, strk wrote:
The function exists within GEOS, which is a library used by PostGIS.
But the specific functionality (snapping) isn't exposed in SQL yet.
What you could do is implement or fund implementation of
the missing bit (the wrapper).
I've always found snapping a very important function in all kinds of
(carto)graphic environments. Could you give an indication how much
time it would cost to write the PostGIS wrappers? If the algorithm
already exists in GEOS, exposing it in PostGIS doesn't look like a
major problem to me.
Jan
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