Hi John,
Regarding snapping points to lines, postgis does not have a built-in
function to do that, but this nice post gives you a good guide on how
to accomplish it: http://blog.cleverelephant.ca/2008/04/snapping-points-in-postgis.html
Regarding how to do a 'Dissolve' in postgis, I assume you are
referring to the Dissolve command equivalent in ArcGIS where polygons
with shared boundaries are merged or otherwise turned into
multipolygons wen they share a common attribute? In postgis this is
done by the combination of the ST_Union() function on the geometry and
a Group By on an attribute. Something like:
SELECT ST_Union(the_geom) INTO dissolved_polygons FROM your_table
GROUP BY your_attribute;
If you want to run that step with a faster function then read the wiki
post here to learn how to use the new/proposed cascaded union function:
http://postgis.refractions.net/support/wiki/index.php?upgis_cascadeunion
Dane
On Oct 6, 2008, at 1:35 PM, John Zhang wrote:
Hi there,
I am writing to check how to perform SNAP and DISSOLVE function by
PostGIS.
I have a point dataset table and a MultipleLineString dataset table.
I need to snap all the points in the dataset to the Line Strings
when the distance is within 100 meters.
I also need union some polygon features and dissolve the polygons
within a polygon.
Any inputs would be appreciated.
--
Sincerely,
John Zhang, M.Sc., B.Sc., A.Dipl.T.
email: [EMAIL PROTECTED]
Phone: 604-998-1874
URL: http://ca.geocities.com/john_z04/JOHN_ZHANG_GIS.html
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