How fusing tactical inertial sensors with Low Earth Orbit satellite Doppler eliminates transoceanic navigation drift.
Autonomous commercial container vessels navigating transoceanic corridors operate far beyond the reach of terrestrial cellular networks. If GPS signals are spoofed or lost due to solar flares, standard dead-reckoning drift causes vessels to stray kilometers off course within hours.
NTNNavigation implements tightly-coupled integration: rather than computing separate position fixes and averaging them, raw pseudorange and Doppler measurements from overhead LEO communication satellites are directly injected into the inertial Extended Kalman Filter (EKF). Even when only two satellites are intermittently visible, the system updates velocity vectors and arrests inertial drift. ``` +-----------------------+ Raw Doppler & Range +-----------------------+ | LEO Communication Sat | --------------------------------> | Tightly-Coupled EKF | | Ephemeris & Doppler | | Joint State Vector | +-----------------------+ +-----------------------+ ^ | | v +-----------------------+ +-----------------------+ | Tactical MEMS IMU | --------------------------------> | Autonomous Autopilot | | Gyros & Accelerometers| 500 Hz Kinematics | Sub-Meter Track Hold | +-----------------------+ +-----------------------+ ```
During Arctic transit trials where traditional GPS satellite elevation angles were near the horizon, NTNNavigation maintained 0.4-meter navigational accuracy, completely eliminating gyro bias drift.