[Proj] Conversion from WGS84 to UTM31

[Clifford J Mugnier]

Fabien,

The difference in the shift parameters offered by Circe2000 and my column
on Spain are likely the difference between the transformation parameters
between France and Spain.

You may get better correspondence with EU50 coordinates in Spain if you use
those parameters published for Spain.

I thought you said that you are in Spain ... ?

Happy Mardi Gras!

Clifford J. Mugnier
Chief of Geodesy
CENTER FOR GEOINFORMATICS
Department of Civil Engineering
CEBA 3223A
LOUISIANA STATE UNIVERSITY
Baton Rouge, LA  70803
Voice and Facsimile:  (225) 578-8536 [Academic]
Voice and Facsimile:  (225) 578-4474 [Research]
======================================================
http://www.asprs.org/resources/GRIDS/
http://www.cee.lsu.edu/facultyStaff/mugnier/index.html
======================================================



> > > 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