Thanks , that explains things a bit better , but rangepoint must be way better than 150mm as that wouldn't be any use for drillingRange point won't put the tramlines in the same place year on year. RTK will do that so if you're doing controlled traffic its ideal as you can swap AB between machines and it will always be in the same place. Also RTK is 2cm accuracy pass to pass, and rangepoint is 15cm though I think people say it is a lot better than 15cm in practice. If you are doing bed forming for spuds etc the RTK is the best option, though people make lesser accuracy setups work well. It will always be dead straight its just how accurate the next bout will be. So if using markers you can line up on the marker line, nudge your AB line to that, and then set off. There are so many different options around its mind boggling! As @Chae1 says rangepoint is good enough and I think its only £265 a year with first year for free.
Maybe some rangepoint users will advise the actual,accuracy