[Proj] Conversion from WGS84 to UTM31

[Fabien Brachere]

Le mardi 28 février 2006 à 15:55 +0200, Martin Vermeer a écrit :
> On Tue, 2006-02-28 at 13:55 +0100, Fabien Brachere wrote:
> > Le mardi 28 février 2006 à 13:25 +0200, Martin Vermeer a écrit :
> > > On Tue, 2006-02-28 at 11:42 +0100, Fabien Brachere wrote:
> > > 
> > > Hello ,
> > > I'm trying to convert data from my GPS to UTM31 coordinates and I use
> > > something like that:
> > > 
> > > ./cs2cs -v +init=epsg:4326 +to +init=epsg:23031
> > > 
> > > Surely there must be a datum offset... UTM31 coordinates on the
> > > international ellipsoid sounds like a terrestrial, non-geocentric datum,
> > > even if the <23031> entry doesn't provide one. 100 m sounds about right.
> > > 
> > > - Martin
> > 
> > Thank you Martin, I think the datum is ED50 but I don't know how to
> > apply the offset, with towgs84 parameter or a grid ? If yes, do you know
> > where I can find the datum offset or the grid ?
> 
> Google is your friend...
> 
> dx = -84 m +/- 5 m
> dy = -107 m +/- 6 m
> dz = -120 m +/- 3 m
> 
> see http://www.asprs.org/resources/grids/07-2000-spain.pdf
> 
> - Martin
> 

Thank you very much, I finally find the offset in Circe2000 (the
software I mentionned above):
dx = -84 m
dy = -97 m 
dz = -117 m

I put it here for interrested people.

-- 
Fabien Brachere <fabien.brachere at eikonex.net>
Eikonex