sentences:  The use of stars as a reference system was expanded in the 70s and early 80s for continental networks, but then the laser and electronic measurements became better than 2 m and could be carried out automatically.Nowadays some similar techniques are carried out by interferometry with very distant radio quasars instead of optical satellite & star observations.The geodetic connection of radio telescopes is now possible up to mm–cm precision as published periodically by the IVS community.