Обсуждение: Search by distance

HI,

I would like to implement a search by distance to my application.

Something like (pseudo sql):

select * from users
where users.location is less than 15 miles from chicago.

Any documentation on how to implements that?

I guess I also need a database of the cities coordinates. Where could I find one?

Thanks

Oscar

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Oscar Picasso wrote:

> HI,
>
> I would like to implement a search by distance to my application.
>
> Something like (pseudo sql):
>
> select * from users
> where users.location is less than 15 miles from chicago.
>
> Any documentation on how to implements that?
>
> I guess I also need a database of the cities coordinates. Where could
> I find one?
>
> Thanks
>
> Oscar
>
> ------------------------------------------------------------------------

I can't help you with the coordinates, but this is exactly what the
contrib package PostGIS is designed for.

Jeff

Oscar Picasso wrote:

> I guess I also need a database of the cities coordinates. Where could
> I find one?

You can download US data here:

   http://geonames.usgs.gov/domestic/download_data.htm

These are tables of geo entities with a number of columns, including
lat/long.  NGA (formerly NIMA) has similar data for non-US entities:

   http://earth-info.nga.mil/gns/html/cntry_files.html

Note that these data sets include =lots= of entities, not just cities -
we've combined them into a DB with about 6 million items, and only
about 2.5 million are population centers (by our scheme).  Each of the
data sets has feature type columns that you can filter on, though.

- John Burger
   MITRE