ENR 4.2 Special Navigation Systems

1.. Doppler Radar

1. Doppler Radar is a semiautomatic self-contained dead reckoning navigation system (radar sensor plus ­computer) which is not continuously dependent on information derived from ground based or external aids. The ­system employs radar signals to detect and measure ground speed and drift angle, using the aircraft compass ­system as its directional reference. Doppler is less accurate than INS, however, and the use of an external ­reference is required for periodic updates if acceptable position accuracy is to be achieved on long range flights.