I gather the OP wants to do it the hard way, hence his insistence on
ignoring all the excellent commercial software available at the present
time.

I actually already have a chartplotter with the some Baltic charts
in vector format. But I can't access the charts from my PC.
The only nice thing I can say about this chartplotter is that
the screen is pretty good, the rest is rubbish.

Whilst admitting that some of this software costs money, I don't think this
is the OP's reason for wanting to "go it alone".

Me? I enjoy sailing too much to spend hours re-inventing the wheel! Oh, and
I do have charts of the Baltic, I just don't sail there!

Interesting idea, so:

- Microsoft makes Internet Explorer, so Firefox-people you are just re-inventing the wheel..
- Microsoft already makes Office, so why do the Open-office group bother ?
- etc

No seriously, I would like to do it because it amuses me.
Besides, can't sail here between November and April so maybe working on
this project during the winter gives me some feeling of how nice it is to
be out there sailing...

Josce