[josm-dev] projection Mercator, set EPSG 3785 instead of EPSG 3857

[Tobias Wendorff]

Am 25.02.2011 20:13, schrieb M∡rtin Koppenhoefer:
> I know that EPSG says "NOT VALID". Who cares?

EPSG are creating and releasing the codes. You have to face *why*
they do that. They need it for surveys and for geodetic use.

EPSG:3785 uses a sphere, which is "outdated" nowerdays. But it's
much more easy to use in OSM. A simple formular with good looking
results.

EPSG:3857 uses an ellipsoid, which is more equal to real Earth,
since it uses WGS84 as background.

For OSM, it would be much better to use EPSG:3857 instead of
EPSG:3785. The reason is: our coordinates are in WGS84. Normally,
you have to transform the WGS84 ellipsoid to some WGS84 sphere
to get correct results, but noone does this.

When using EPSG:3857 you're in "one system" and you don't have
to transform anything. But the formulars to draw the map are
much more complicated, since you have to deal with integrals
or expansion in series.

HTH
Tobias