Dead reckoning is a navigation method that estimates a vessel’s current position from a known starting point, then updates it using course, speed, and elapsed time. It does not depend on external signals such as GNSS or GPS, which makes it useful when satellite positioning is jammed, spoofed, blocked, or otherwise unreliable.
In cyber security, dead reckoning is a resilience control. When attackers inject false location data or disrupt navigation feeds, crews can cross-check the digital position against radar, visual bearings, and inertial or speed-based estimates. This helps detect spoofing, reduce overreliance on compromised data, and keep bridge systems from accepting a misleading track. Dead reckoning is not perfectly accurate, but it provides a crucial fallback that can preserve situational awareness until trusted signals return.