[postgis-users] Distances from geometries other than points

[Julian Scarfe]

From: "Markus Schaber" <schabi at logix-tt.com>

> If all your objects are in a relatively small area and not distributed
> over the whole planet, you can project() them

Unfortunately they are globally distributed, so they would need a different 
projection for each query.

> Well, the best doc should be the PostgreSQL documentation about writing
> C functions, and the best examples should be the PostGIS sourcecode 
> itself.

Yes, I already have some of the functions for PostgreSQL points using 
spherical (rather than spheroidal) trig.  But PostgreSQL points and rtree 
indexes are, of course, much less capable than PostGIS and GiST when it 
comes to planning spatial queries, hence I really have to think about 
PostGIS in the medium term.

(See also http://archives.postgresql.org/pgsql-general/2005-04/msg00419.php 
for my discussion with Tom Lane on this.  Any corrections to my 
misconceptions about PostGIS in that thread would be welcome.)

> I also invite you to submit your changes back to the PostGIS
> project for inclusion. :-)

Thanks Markus, I'll certainly consider that if I get anywhere.  Your message 
served as a useful reminder, as PostgreSQL itself is not GPL.

Julian