With GPS having at best three metres accuracy? Regular unaugmented GPS actually has something like 10m-3m of error. GNSS augmentation, like WAAS, gets you down

With GPS having at best three metres accuracy? Regular unaugmented GPS actually has something like 10m-3m of error. GNSS augmentation, like WAAS, gets you down to 1m. RTK GNSS gets you down to 1cm, but you need a stationary base station, and accuracy gets worse the farther away from the station you are. A REACH RTK pair costs $570: https://emlid.com/shop/reach-rtk-kit/ https://emlid.com/shop/reach-rtk-kit/ You can get down to 1mm of error with good antennas and long-term averaging-- no good for moving objects. This is how we measure continental drift.