Making my own coordinate system

This is less of a real code question and more of a conceptual one.

Imagine an area that we will call our galaxy. The galaxy has a diameter of 100,000 lightyears, and is, say 2,000 light-years tall. I want to divide this area into reasonable "chunks" as a means of not only easy orientation, but as a means of circumventing the current floating-point limitations.

My idea for the heirarchy is this:

• Top or bottom half, then quadrants of 50k ly (we could also do an octant system, but I don't like that for some reason)

• Each quadrant has 4x4x4 "cubics" of 12500 ly

• each cubic has 5x5x5 sectors of 2500 ly

• each sector has 10x10x10 subsectors of 250 ly

• one more division of 10, now each is 25 lightyears

• I kinda want one more division

We can essentially see that I have divided this area into 25x25x25 lightyear cubes, and we can represent all possible coordinates as xyz = -+, 1-4, 1-64, 1-125, 1-1000, 1-250, 1-25, meters. The idea is to scale the largest possible coordinate from whatever 100,000 lightyears is to something more manageable (in our case 25 lightyears worth of meters) , but to be honest I really don't know how practical this idea is. The largest distance is still way too large, and the resultant coordinate system really doesnt work all the well either, but I feel like i'm on the right track.

Does anyone have any better ideas? Am I overthinking this? If anyone has any form of insight at all, I would appreciate it. Also, I do not need any code examples, just concepts.