[Proj] DHDN / Gauss Krueger to WGS84

[Oliver Eichler]

> I do have a coordinate in easting/northing [m] from a raster map  using
> Gauss Krüger projection and Potsdam datum. Now I would like to get the
> lon/lat coordinate on a WGS84 ellipsoid. And vice versa. I would like to
> use the proj4 C API not the command line.
>
>   

Ok, further investigations condensed into something like:

pjgaukru = pj_init_plus("+init=epsg:31467");
pjwgs84 = pj_init_plus("+init=epsg:4326");

// easting / northing to lon / lat
pt = pj_inv(pt,pjgaukru)

//???
double z = 0;

pj_datum_transform(pjgaukru, pjwgs84, 1, 0, &pt.u, &pt.v, &z);

However the result is still several minutes away from the expected
coordinate. What do I miss?

Oliver