The first idea seems the better of the two - like you say that's a lot of data to enter otherwise.
Wasn't sure if the journal held coordinates of the systems that you had visited though, in which case it could be calculated on the fly.
G
I hadn't considered that, but the Journal system actually tells me the coordinate position of the main star for the system you jump into! I could include that in the system data and using that to calculate distances between systems is relatively easy!
(It also tells you the fuel used for the jump, and remaining fuel in the ship which is interesting, I might use that too)