[postgis-users] Multi centroids

[Paragon Corporation]

Mike,
I think what you may want is 

SELECT gid, field1, field2, ST_Collect(the_centroid) As multicentroid
FROM (SELECT gid, field1,field2, ST_Centroid((ST_Dump(the_geom)).geom) As
the_centroid FROM sometable ) As foo
GROUP BY gid, field1, field2

Hope that helps,
Regina

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Mike
Toews
Sent: Friday, December 05, 2008 4:55 PM
To: postgis-users at postgis.refractions.net
Subject: [postgis-users] Multi centroids

Hi,

Is there a simple way to extract the multiple centroids as MULTIPOINT
geometries from MULTI* objects (i.e., ST_MULTICENTROID(geometry) )? The
ST_CENTROID function only returns POINT geometries.

(An example application of this is to initially place CAD labels for
MULTIPOLYGON features, since it appears that AutoCAD is not smart enough to
place these properly, and need manual adjustment to avoid label conflicts. I
have always been baffled by the purpose of multipoints until now.)

I'm guessing this isn't a built-in function and the solution will be a
custom SQL or PL/pgSQL function. Thanks for any help/ideas.

-Mike

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