[Proj] Converting Mercator Meters to Degrees

[Mikael Rittri]

I suspect your direct formula doesn't use the appropriate value for the
Earth radius.

CP>   longitude = (MMEasting / 6356752.3142) * 57.295779513082322;
CP>   OR longitude = (easting / earthRadius) * RadToDeg;

That value looks like some kind of average earth radius for a spherical
earth model.  
But I think you must use the equatorial radius of the WGS84 ellipsoid,
which is 

   6378137.0 meters

see, for example, http://home.online.no/~sigurdhu/WGS84_Eng.html

Best regards, 
  Mikael Rittri, Carmenta, Sweden. 

-----Original Message-----
From: proj-bounces at lists.maptools.org
[mailto:proj-bounces at lists.maptools.org] On Behalf Of Christopher Portka
Sent: den 1 februari 2007 18:43
To: proj at lists.maptools.org
Subject: [Proj] Converting Mercator Meters to Degrees

I'm trying to convert a UTM easting value to an easting in mercator
meters and then to its correct longitude.  
[ ... ]