[PROJ] Help with transformation of GPS coordinates to TK25

[support at mnspoint.com]

Hello,

don't assume anything else but that everything given has errors.

If you get some offset where it should not be, you have either

1) Wrong datum.
2) Missing datum.
3) Datum where datum should not be.
4) GPS coordinates are actually in WGS84 (but not told so). [fix your 
GPS]
5) GPS coordinates are actually in some datum (but not told so). [fix 
your GPS]
6) Try to google the right datum for that area and use it instead.
7) Some wrong parameter (many possibilities)
8) etc.

Mostly it is a datum error ... you are using wrong datum in some point 
of the conversion or assuming something that is not true.

Usually modern GPS's give coordinates in WGS84 datum by default (so 
assume that). And then convert those to TK25 datum. If the device is 
preset to Germany then it most likely uses some modern datum like 
Gauss-Krueger (zone 2, 3, 4 or 5) or UTM (zone 32 or 33). Then you have 
to convert for example UTM 32 -> TK 25. Looks like a datum error.

Janne.

-------------------------
> So, _where_ is the offset coming from?  I really don't know how to
> fix this?