[OSM-dev] Algorithm for converting lat/lon into Mercator as used in OSM PostGIS?

Nick Whitelegg nick at hogweed.org
Sun Mar 11 11:24:41 GMT 2007


Hello Artem,

> Nick,
>
> see below
>

Tried this (literally direct copy and paste) but I don't get the same answer 
as the Mapnik conversion. For example, with bbox -0.75, 51.02, -0.7, 51.07 
here is what I get from a test program:

Mapnik projection conversion, using PROJ.4 (correct with respect to the 
PostGIS database):

-83489
6591595
-77923
6600425

Older OSM Mercator conversion code:

-83489
6624832
-77923
6633685

Your sample code:

-4783602
5317872
-4464695
5764860

The last one seems to be in the wrong scale, as the box is supposed to be 
about 6km x 9km. Are there any other parameters I need to set?

Thanks,
Nick




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