Firstly, why is there a galaxy plane at all ? I dont know the exact physics answer but I know its to do with it having a low energy state. I assume that when stuff has movement (kinetic energy) in random directions and in space with gravity then everything starts to orbit. I am guessing that collisions occur removing energy of the system from some directions until you have an overall moderately stable system. I know that if all the orbits were in a spherical bound then they can lose energy and keep orbiting by flattening out. I cant remember why exactly tho - something about angular momentum and stuff like that. So galaxies tend to go flat - especially at the edges.

So this map being on the outer rim of the galaxy is sorta flat and I have chosen to use cylindrical coords to map sectors. So the first number is the rotary value, the second is the radial value and the third is the Z height from the plane. Since this one is 000 then its the one on the plane so this sector has the plane going right through it. I have arbitrarily chosen it to be in the middle. I am guessing that like the earth is not perfectly spherical the galaxy does not have an exact plane either though I would think that with the number of stars present then a really precise figure of where that abstract plane lies could be determined.