[OSM-dev] osmarender+tiles at home projection bug

Jochen Topf jochen at remote.org
Thu Feb 15 10:19:24 GMT 2007


On Thu, Feb 15, 2007 at 12:02:12PM +0100, Andreas Brauchli wrote:
> > Osmarender 
> > a) can't do proper trig and is using a simpler approximation to cos()
> > (this could be improved by adding more terms), and  
> > b) because you can't do a function call, is using a constant
> > transformation across a whole render.
> might that be a solution:
> 
> 1. create the svg untransformated (no cosine approximation)
> 2. postprocess the svg to correct the projection - a simple perl script
> could do that
> 
> it creates the burden of chaining operations, especially if we're not
> rendering large areas where the correction isn't that obvious

It would be much easier to do it the other way round: Pre-process the
OSM file and add projected coordinates to it and then let Osmarender do
its thing. Its easier because you just have to look at all the @lat and
@lon attributes of the nodes while in SVG there are many places which
have coordinates.

Frederik has done some work on that. See
http://wiki.openstreetmap.org/index.php/Osmarender_bug .

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





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