Distances between systems aren't known because inter-system travel is exclusively by wormhole. Yes, that's right, gate camping, bottlenecks, zones of control, ... shit like that. What can you do?
Well, some people have suggested adding faster than light (FTL) travel to the game. In the game now, the fastest speed is 0.2c. Once area compression is taken into account the effectual speed works out to be 1.6c.
At 1.6c it would take 2.73 years to reach Alpha Centauri, our solar system's nearest neighbour. About 1000 days. So, in game play terms, in order to get there in a whopping TWO days we would have to fly 800 FTL. It's a game, so why not? Well, Star Citizen has 100 - 400 systems planned with several planets, asteroid belts, stations, and whacks of other stuff all littered about. The reality of Alpha Centauri would limit things greatly.
The nearest system to Earth in Star Citizen is Croshaw. It is an unknown distance away. It could be twelve bazillion light years. We don't know! But we get there by a wormhole ... 20 minutes, tops. The effectual distance from Earth to Croshaw is actually just the distance from you to the Croshaw wormhole entrance. It's kinda irksome knowing that there may be all kinds of alien civilizations between Earth and Croshaw.
Distances are very difficult to discern in Star Citizen. Most maps simply show size relationships between systems. Size being whether large, medium, or large ships can enter the wormhole. I'm unaware of any map that shows distances. So I started making one.
I'm using rudimentary network graphing software to do this. I no longer have software languages such as Python or graphics packages such as igraph. But it seems to be working, sorta.
This is a SIZE relationship map. There are lots out there (see last post). It shows,via line thickness, whether a small, medium, or large ship can jump through a wormhole. Distance, counter-intuitively, is not relayed at all so don't be fooled.
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Thickness of connecting line portrays size of ship that may pass.
For comparison, the following is a DISTANCE relationship map. The thickness of the connecting lines implies distance: narrow for short distance, medium for medium distance, and thick for far distances. Remember to keep in mind that the length of the connecting lines is not relevant.
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Thickness of connecting line portrays distance between points.
It is just a partial network. I edited in the distances as my software wouldn't display the strength of the line, it just adjusts thickness of it. Need to pay extra for labeling, I guess. Anyway, I plan on expanding this for the whole Star Citizen galaxy.
Oh, I should mention the software used: Google Fusion Tables. It's free.