Determining the distance between 2 locations, or bases, is important for things like managing your Trade Routes. Maybe you want a minimum distance of 3000, and want to know the Galaxy range that you will be looking for.

To determine distance in Astro Empires, you have to know how the Galaxies are set up. Galaxies are set up in groups of 10. Let's us use the Alpha server as an example:
A00-A09
A10-A19
A20-A21
and so on.

The distance inside a group is 200 "units" per Galaxy, so the distance from A00 to A01, is 200 units. Or A01 to A02, it would also be 200 units. The distance from A00 to A02, however, would then be 400 units.

The distance from A00 to A09, 9 Galaxies so it would have a distance of 1800 (200x9 Galaxies).

Travel between 2 groups however, is 2000 units. so to travel from A09 to A10, it would be 2000. Travel from A09 to A11, would be 2200, 2000 for the group change, and 200 for the distance between A10 and A11.

So returning to my first paragraph, about wanting to know the Galaxy Range for a Trade Route with at least 3000 distance, if I was in, A30, I would want a Trade Route to someone in A24 or lower, or A40 or higher, although in the case of the distance from A30 to A40, the distance would be 3800 (1800 for the distance from A30 to A39, and the 2000 for the distance from A39 to A40).