Re: Earth distance

On Thu, 2003-03-27 at 08:40, Stephan Szabo wrote:
> On Thu, 27 Mar 2003, Bruno Wolff III wrote:
>
> > On Wed, Mar 26, 2003 at 18:29:42 -0600,
> >   Tad Marko <tad@tadland.net> wrote:
> > > Bruno,
> > >
> > > I aplogize for bothering you direclty, but I'm having some difficulty with
> > > some syntax using the earth distance functions. Every single example I can
> > > find is using hard coded constants for the latitude and longitude, but I'm
> > > trying to use a join to get these values. Basically, what I'm trying to do
> > > is:
> > >
> > > select up.first_name, up.last_name, up.city, zip_code from user_primary as
> > > up, ziplocs as zl where zl.zip=up.zip_code::integer and '(33.0, 97.1)'::point
> > > <@> '(zl.lat, zl.lon)'::point < 50;
> > >
> > > But this fails with a
> > >
> > > ERROR:  Bad point external representation '(zl.lat, zl.lon)'
> > >
> > > message. I simply cannot figure out how to specify the lat and lon values
> > > from the joined table. Can you offer any suggestions?
>
> That'd attempt to make a point from the string literal given, not what you
> want.  I think point(zl.lat, zl.lon) might work (there's a point function
> that takes two doubles and returns a point).

Excellent! That's all I needed. I just hadn't come across the point
function in the documentation (searching on point yields quite a pile of
responses at the Postgres site), and I'm starting to doubt the value the
O'Reilly book on Postgres.

Now all I have to do is figure out how to deal with the issue of
canadian zip codes that we have mixed in.

Thanks!

Tad

--
Tad Marko <tad@tadland.net>