[Proj] [Newbie] Conversion from wgs84 to tmerc

[Roland Rickborn]

Hi folks,

I'd like to convert wgs84 coordinates from all over Europe to tmerc
(Gauss-Krueger).

According to David Vaz' posting "cs2cs how to use" (posted on Feb. 15,
2006, [1]) it is not that easy to convert?!

> You cannot go directly from WGS84 Datum coordinates to a projection (tmerc)
> on another Datum without FIRST performing a Datum Shift.


Searching the web, I found the following information [2]:

> I got the same problem as Harald Wehr when tranforming from wgs84 to
> Gauss-Krueger (zone 4).
> I use cs2cs as follow
> cs2cs +proj=latlong +datum=WGS84 +to +proj=tmerc +ellps=bessel
> +lat_0=0 +lon_0=12 +x_0=4500000 +towgs84=583,68,399

Presumably, this applies (to a certain part of) Germany!?

My questions are:
how can I determine lon_0 (central meridian) and x_0 (left shift) for 
many different locations in Europe? All I have are the geographic 
coordinates and the geographic coordinate system. E.g.:

ID|GeographicCoordinateSystem|Longitude|Latitude|CountryID
1|"WGS84"|9.183132|53.904484|DE
2|"WGS84"|6.764922|38.33335|ES


[1] http://lists.maptools.org/pipermail/proj/2006-February/002100.html
[2] http://lists.maptools.org/pipermail/proj/2002-June/000378.html
[3] http://www.grass-gis.de/lit_html/grasshandbuch_v12/node172.html (german)

Any hint appreciated.

TIA,
Roland R.