Inertial Navigation System (INS)
An Inertial Navigation System (INS) is a self-contained navigation system that uses accelerometers and gyroscopes to track the aircraft’s movement from a known starting position, computing position, velocity, and attitude without reference to external signals. INS requires no radio signals and works in any environment — over oceans, in the Arctic, or during radio jamming.
How INS Works
Three accelerometers (one per axis) measure acceleration. The system integrates acceleration over time to derive velocity, and integrates velocity over time to derive position. Because position is calculated by double integration, any measurement error accumulates over time — INS accuracy degrades with time since the last alignment.
INS in Modern Aviation
Modern aircraft use Inertial Reference Systems (IRS) — a more accurate, solid-state evolution of INS. IRS is coupled with GPS in most flight management systems to provide continuous position correction. IRS maintains full navigation capability during GPS outages, while GPS corrects the slow IRS drift. This hybrid approach is the standard in commercial aviation.