Tech focus: Doppler navigation system for backup and verification of GPS

摘要

The proposed autonomous navigation concept incorporates a radar altimeter, multiple forward-looking (and possibly aft-looking) pulse Doppler radar beams, and a site-specific airborne radar clutter model to aid in aircraft navigation under conditions when GPS service is interrupted. Additionally, this system may be used as a means of periodically verifying the navigation outputs of a GPS system. Over water or relatively smooth terrain, the surface-clutter returns from the pulse Doppler radar beams are used to compute the true ground speed of the aircraft; the Doppler shift in the clutter will be a function of the platform speed and heading and the known pointing angle of the beams. The ground speed estimates and altitude estimates from the radar altimeter and a known initial starting location can be used to compute the platform navigation outputs.