3CD or 3TX data

Hej!

I am completely new to the world of digital maps and geographical data. 
Currently I studying in Sweden and working on a study project, 
concerning movements of aircraft. As an input for the simulation program 
I have to use, I need topographical data. Therefore I am searching for a 
source of such data for Sweden, which is provided or can be converted 
into the 3CD or 3TX format.
Does anybody of you know where I can find such data? I already searched 
at www.lantmateriet.se but I don't know if those maps are what I am 
searching for and they are quite expensive... So it would be really 
great if you could help me!

Thanks in advance for your help.

/Michael