[OSM-dev] Mapnik projection slightly wrong?

[Artem Pavlenko]

On 23 Sep 2008, at 16:30, Jan-Benedict Glaw wrote:

> Hi!
>
> I just looked at applications/rendering/mapnik/ 
> generate_{image,tiles}.py
> and noticed the projection string:
>
> 	+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0
> 	+y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs +over
>
> `a' and `b' are ment to be the equatorial and polar radius of the
> earth. Since we all use GPS, I guess we want to use the WGS84
> ellipsoid, where the polar radius (b) would be 6356752.315m, instead
> of 6378137.000m?  Is this intentional?  At least, osm2pgsql uses the
> same, so all of the users are identical :)

This is what G.Y.M is using. The earth is a perfect sphere :)
Artem
>
>
> MfG, JBG
>
> -- 
>      Jan-Benedict Glaw      jbglaw at lug-owl.de               
> +49-172-7608481
> Signature of:  The course of history shows that as a government  
> grows, liberty
> the second  : decreases."  (Thomas Jefferson)
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