[postgis-users] issue with pgsql2shp

[John Cole]

I'm trying to create shapefiles from tiger data inside our postgis database
with pgsql2shp.  Since these shapefiles are for rendering with mapserver
only, I'd like to pre-process these so they are optimal for rendering at
certain scales and maximize mapserver performance.  I'm using "1.0
USE_GEOS=1 USE_PROJ=1 USE_STATS=1" of PostGIS.

Here are some issues I've run into:

1)  If I give pgsql2shp a query like "select the_geom from tgr_roads where
cfcc like 'A1%' or cfcc like 'A2%'", I get the following error; ERROR:
Cannot determine geometry type (empty table).  I found a mail list message
from 2003 about adding a -t switch to specify the geometry type, but that
doesn't appear in this version.  I'd like to do this without creating
temporary tables.

2)  I'd like to make reduced resolution shapefiles for certain scales (for
example, at 1M scale, no feature should be shorter than 250 meters, the size
of one pixel on the map).  Does the simplify() function do this?  I have the
following query, which I think does this, but I get the same error as in 1)
above.

select transform(simplify(transform(collect(the_geom),32616),250), 4326) as
the_geom from tgr_roads where cfcc like 'A1%' or cfcc like 'A2%' group by
hwy_num, rd_name

3)  I don't see the equivalent densify() ArcInfo function in PostGIS, is
there one?  When creating reduced resolution shapes, I like to densify they
line to 1-10 meters and then reduce the resolution to 250 meters to ensure
that the original shape of the file is retained.

Thanks,

John Cole 
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