While the use of GNSS – more commonly known as GPS – is now widespread, the signal itself comes from satellites that are 20,000 kilometers away, making it fairly weak and subject to loss of signal or interference. For military operations, this presents several challenges. In a recent naval exercise, a scenario of GPS denial triggered up to 48 shipboard systems to generate alerts when GPS was lost. This shows how GPS is so pervasive and deeply integrated into many military systems for air, land and sea.