Francisco,
ST_Distance (you can think of as min distance) returns the shortest distance
between 2 geometries. So between a point
and a poly, if the point is in the poly the distance will be 0, it its outside
it would be the distance between the closest point on the surface of the poly
and the point. (there is actually another distance which no one asks about
ST_MaxDistance - which is between the most distant point of a poly to a point -
anyway I just mention it, but you wouldn't want to use it here).
Your below query won't use indexes since ST_Distance doesn't use an index. Use
ST_Dwithin instead
SELECT p.gid as id_parcela,tipo as tipo_Pozo
FROM selepozo(1,1) po,parcelas p
WHERE ST_DWithin(p.the_geom, po.the_geom, 1)
http://postgis.refractions.net/documentation/manual-svn/ST_DWithin.html
Hope that helps,
Regina
-----Original Message-----
From: [EMAIL PROTECTED] on behalf of fsalas
Sent: Fri 10/3/2008 7:01 AM
To: [email protected]
Subject: [postgis-users] about st_distance
Hi,
I need to know about obtain distance between polygon( parcels) and point
I Use the next sentences
SELECT p.gid as id_parcela,tipo as tipo_Pozo FROM selepozo(1,1) po,parcelas p
WHERE ST_distance(p.the_geom, po.the_geom) < 1
I have some questions
This distance is between centroide of parcels to point or between border of
parcels to point ?
Best Regards,
Francisco Salas
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