Re: locating cities within a radius of another

Oliver Kohll - Mailing Lists wrote:
>
> On 21 Jul 2010, at 23:14, Joe Conway <mail(at)joeconway(dot)com
> <mailto:mail(at)joeconway(dot)com>> wrote:
>
>> If you want something simple, and not requiring PostGIS, but plpgsql
>> instead, see:
>>
>> http://archives.postgresql.org/pgsql-sql/2003-12/msg00193.php
>
> For completeness, the earthdistance module also provides the distance
> between two lat/longs, the point<@>point syntax is simple to use:
> http://www.postgresql.org/docs/8.3/static/earthdistance.html

Trying to figure out the proper usage. My assumptions:

use ll_to_earth() to get point values to pass to 'point <@> point'

First issue, ll_to_earth() returns three values, not one.

Second issue, I tried something like:

select (ll_to_earth(46,67)<@>ll_to_earth(57,87));

I get:

ERROR: operator does not exist: earth <@> earth
LINE 1: select (ll_to_earth(46,67)<@>ll_to_earth(57,87));

So I tried:

select (4618419.15006707<@>4394453.66154081);

And I get:

ERROR: operator does not exist: numeric <@> numeric
LINE 1: select (4618419.15006707<@>4394453.66154081);
^
HINT: No operator matches the given name and argument type(s). You
might need to add explicit type casts.

What am I missing???

--
Until later, Geoffrey

"I predict future happiness for America if they can prevent
the government from wasting the labors of the people under
the pretense of taking care of them."
- Thomas Jefferson