[OSM-talk] project

[Torsten Mohr]

Hello,

i created a GIS database and imported the planet data with osm2pgsql -m.
So the data is stored in mercaator format.

When executing this raw SQL query:

select st_X(way), st_Y(way), name from planet_osm_point where capital='yes';

Then i get some data like:

       st_x        |       st_y        |            name
-------------------+-------------------+----------------------------
  -18915583.203791 | -2162182.86527014 | Alofi
 -11035458.4801666 |  2205926.10968281 | Ciudad de México
 -10075876.3988655 |  1648035.49949994 | Guatemala City

How can i reproject the st_x and st_y to latitude / longitude?

I'd like to do this in an own program.  I already reprojected some
Tiff data from latitude / longitude to mercaator, that worked fine.

But i don't know what st_x and st_y actually are, how they are scaled,
what is their offset.  The documentation for st_X and st_Y didn't help
me for this issue.

Can anybody please explain to me what st_x and st_y are, how they are scaled,
what is their offset so i can reproject these data to latitude / longitude?


Thanks for any hints,
Torsten.