[postgis-users] US counties to Spatial_ref_sys?

[Darryl Watson]

Hi all-

I'm a noobie who has been lurking for months on this list, and need a 
nudge in the right direction.  I feel like I may have all the data I 
need at hand, but am not quite putting the parts together.

Here's my PostGIS_Full_Version() string:

"POSTGIS="1.0.3" GEOS="2.1.3" PROJ="Rel. 4.4.9, 29 Oct 2004" USE_STATS 
DBPROC="0.3.0" RELPROC="0.3.0""

I'm trying to determine which SRID to use for a given lat/long point.  
These points will always be within United States boundaries.  I have 
created a table with county polygon data from the US Census Bureau, 
which is close enough for my purposes. I am using boundary data from 
this source:

http://www.census.gov/geo/www/cob/co2000.html

I can then run a query to find which county a given lat/long point is 
in.  Question: since I now know what US county my point is in, how can I 
determine the SPCS zone it is in, and how to select the proper SRID from 
the PostGIS spatial_ref_sys, for US feet?  Is there a data table out 
there which has a county to PostGIS SRID mapping?

Any pointers about how to proceed are appreciated!