Pulsars can be used to arrive at celestial positioning accurate to ±5 km. There is a test rig on the ISS that has validated this. No need to build human made beacons when the universe has so graciously provided us with them.
They plan to get within 1km, which is quite impressive for one system alone. Thanks for the pointer (after reading it, I remember having read about NICER, but didn't remember the precision they got)
