Yeah, I can buy that a lot of space is uncharted. It’s just weird that somehow the republic in 35 years, never came across the map in any imperial computers. I’m assuming they would have raided various ships and bases in that time. Unless the only copy of the file was on the Death Star. I’d also like to know how Luke found a complete version of the map.

Edit: Nevermind, according to a post in the TROS discussion thread, Battlefront II explains that Luke found a Jedi compass and used that to find Ach To.