The risk of Global Navigation Satellite ­Systems (GNSS) outages is known to cause disruption to shipping. Much less well known is its ability to provide dangerously misleading data, potentially harming mari­time operations and global trade.

These ships did not discover their coordinates had been falsified until after they returned to port, illustrating how the risk to GNSS signal integrity is less visible and so even more dangerous than the risk of ­signal outages.