[Gdal-dev] [whatever] to WGS definitions?

[Tomas R]

Do there exist any general source for correct [whatever] to WGS 
definitions?

I have an application which by use of GDAL translates WGS coordinates to 
and from [whatever] projection. I have it working with a few fully 
defined WKTs but it is no fun searching the web after all WKTs I 
possibly would need.

So I tried instead to define the Spatialreferences with EPSG-codes 
instead of WKT. And as suspected the result wasn't what I had hoped for 
since the EPSG lacked the toWGS information. The result in the 
projection I tried (RT90 2.5 gon V, EPSG 3021) the transformation was 
offset by approximately 200 meters west and 50 meters north.

Am I correct in that the error occurs because the EPSG-code do not 
specify the toWGS? If I am correct - what approach do you suggest?

The goal of the application, which is written in C#, is to be able to 
take any map the user provides, with or without geodata in it, and serve 
it to another application which internally works with WGS84. That is my 
application is to be able to set up and translate from a projection the 
user selects to and from WGS84.

The Q is simple - any source for correct definitions of [whatever] toWGS 
that I can use?
Or can I make the EPSG-codes work? Or do they work but I have made an 
error?

Yours
Tomas

(repost - wrong EPSG-code in original post)