[Proj] google KML API advice sought

Roger Oberholtzer roger at opq.se
Fri Nov 28 03:39:36 PST 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

OPQ Systems / Ramböll RST

Ramböll Sverige AB
Krukmakargatan 21
P.O. Box 17009
SE-104 62 Stockholm, Sweden

Office: Int +46 8-615 60 20
Mobile: Int +46 70-815 1696

--

"On two occasions I have been asked (by members of Parliament!),
'Pray, Mr. Babbage, if you put into the machine wrong figures,
will the right answers come out?' I am not able rightly to apprehend
the kind of confusion of ideas that could provoke such a question.
  - Charles Babbage 1791-1871)
    English computer pioneer, philosopher

And remember:

It is RSofT and there is always something under construction. 
It is like talking about a large city with all construction finished. 
Not impossible, but very unlikely.




More information about the Proj mailing list