Loss of satellite signal is a well-known operational risk, but few mariners are aware of the threat of GNSS providing a false time, position or direction even when still available.
When these position errors exceed a safe margin of error, they can cause ships to derive and transmit dangerously misleading Information. GNSS is not designed with inherent real-time integrity, which refers to the users’ ability to trust the data and receive timely warnings if it is unreliable.
So-called space-based (SBAS) or ground-based (GBAS) augmentation systems provide information about the accuracy, integrity, continuity and availability of GNSS services. The European Union’s EGNOS program is a prominent example of an SBAS solution. The UK’s recent exit from the EGNOS program means that, although users will still be able to receive EGNOS signals across the UK, they will have no access to the assurances provided by the future EGNOS Safety of Life services – effectively withdrawing assured system level integrity for EGNOS, GPS and Galileo. Read on.