[Proj] google KML API advice sought

Roger Oberholtzer roger at opq.se
Fri Nov 28 06:39:36 EST 2008

On Fri, 2008-11-28 at 12:06 +0100, Jan Hartmann wrote:
> Roger Oberholtzer wrote:
>  > what might be a good choice for the generic projection to use that >
>  > would do this best in proj (I am still using 4.4.9...)?
> Hi Roger,
> Just an aside, if possible, upgrade to the latest version of PROJ 
> (4.6..) or you'll come to grief over datum shifts. Can't you use the 
> projection Google uses itself for its maps (+proj=merc +a=6378137 
> +b=6378137  +lat_ts=0 +lon_0=0 +k=1.000000 +x_0=0 +y_0=0 +units=m 
> no_defs +nadgrids=@null)? This is a spherical Mercator projection based 
> on the WGS84 Datum. You need to apply a correction to compute real 
> distances, as Mercator maps get distorted towards the North/South Poles, 
> but that is a very simple formula I believe.

I could surely try this. This would get me the northings/eastings. How
would I then convert my INS-improved nothings/eastings back into
lat/longs? The gist of my question was really to see which projection I
could most reliably convert back.

Roger Oberholtzer

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