Satellite navigation has transformed Europe’s transport services. The prospect of enhanced navigation applications has encouraged researchers to approach the technical limits: autonomous vehicle developers, for example, would value more precise and reliable data to deliver lane-level guidance. A solution could be to augment satellite signals with ground-based signals. Demonstrating the concept required sub-nanosecond timing accuracy, but no practical calibration method was available to keep the entire system in sync.

https://www.euramet.org/casestudies/casestudiesdetails/news/fibre-optic-based-wireless-positioning0/