What's the distance and unit represented by the squares on the map?

No one knows, I think. You can find A LOT of discussions about Koronus and Calixis maps on Rogue Trader forums.

3 hours ago, Jargal said:

No one knows, I think. You can find A LOT of discussions about Koronus and Calixis maps on Rogue Trader forums.

Darth Smeg used to state with some certainty distances, but he hasn't been around since September of last year.

Technically speaking, isn't exact distance more or less meaningless, given how the Warp distorts time? The way the individual systems are connected via stable transition routes would be more important than physical distance, I think.

(and I have a feeling the maps are supposed to be taken as "accurate" in the same way that medieval sea charts were, complete with "here be daemons" warnings)

If you're traveling without a warp drive it's important.

Even then an idea of the distances will give me an idea of how much time ill pass for the characters which will give me an idea of how much time will pass in realspace. Regardless of the warp messing with time.

Got an official response.

Roughly 400ly in total

Each square is roughly 4ly

Basically irrelevant for conventional travel though.

And the map is flat but space has three dimensions...

2 hours ago, Jargal said:

And the map is flat but space has three dimensions...

Yes, that was mentioned as well. But we're not Tyranids, so hardly matters.

Well, something like http://www.solstation.com/100ly-bs.htm will be very impressive but not very useful...