[OSM-dev] querying mapnik data

[Jochen Topf]

On Thu, Dec 27, 2007 at 03:43:32PM +0100, Joerg Ostertag (OSM Munich/Germany) wrote:
> I would like to query mapnik data directly from the postgis Database. Can 
> anyone give me a hint which SELECT statements I would need to querey all 
> streets in a bounding Box or in the (surrounding) area of a point. I want to 
> use this inside of osmtrackfilter.pl to get and compare against the already 
> existing osm segments(ways)
> Any hints are welcome.

For example:

SELECT name FROM planet_osm_roads WHERE distance(way,
    GeomFromText('POINT(856371.58 6683083.41)', 3395)) < 1000;

will find names of all streets within 1km distance to point 856371.58
6683083.41 (Mercator coordinates).

Mapnik uses the 4 tables planet_osm_line,planet_osm_point, planet_osm_polygon,
and planet_osm_roads. Each has a column named "way" that contains the
geometry. Thats the one you have to query using the special PostGIS
functions. See http://postgis.refractions.net/docs/ for these. (I have
no idea why they are all called "way" when some of them describe points
or polygons.)

The 3395 ist the so-called SRID, the projection used. Mapnik db uses
WGS84 Mercator.

Jochen
-- 
Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/  +49-721-388298