[postgis-users] what's correction gis function to aggregate polygons

[Heitzso]

into a single polygon?

i.e. working with census block data in one table
I want to generate new tables for block-group,
tract, county, etc.

I know how to use aggregate functions for the numeric data
and have used the 'collect()' function to collect the polygons
into the new geometry in current stable postgresql/postgis
combo.  But the resultant collection of polygons is not
really what I want.  I'ld like to drop the interior
boundaries of the polygons and be left with a single
outer boundary polygon of the collect(geom) geometry.

My guesses are:
	boundary(geometry) function
	latest geos cvs library
	latest postgis cvs
to do that, but cannot test because current geos cvs
is unstable at the moment and doesn't build.

So, my question gets back to:

   what really is the correct function to do what
   I'm needing to do (drop interior boundaries)?

   do I need postgis cvs and geos cvs to get
   that functionality?


Thanks!
Heitzso