Jonathan,
you may try contrib/pgsphere http://www.pgastro.org/cgi-bin/wiki.pl?pgSphere
On Sun, 27 Jun 2004, Jonathan Raemdonck wrote:
> I have the following situation:
>
> I'm developing an reverse geocoder, so input is lat/lon coordinate and
> output is the nearest textual location.
> I have a database of +- 2 000 000 records that contains lat/lon and full
> name of the location.
>
> These are the steps I take now:
> 1 'draw' a box around the lat/lon position we have as input
> 2 search the DB for all the points in this box
> 3 measure the distance to each point in the box
>
> This works fine, but step 2 takes too lang for obvious reasons...
> select * from table
> where lat between box_point1_lat and box_point2_lat
> and lon between box_point1_lon and box_point2_lon;
>
> This would require a seq scan for but indexing the table doesn't help much
> either (factor 2) ...
>
> Is there a good way of indexing the lat/lon column so lookup is faster? I
> have looked at PostGis but didn't think it would give a good solution in
> this context (correct me if I'm wrong)
>
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Regards,
Oleg
_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83