Abstract: A terrain bias compensator for a Doppler navigation system utilizes an auxiliary beam with each beam of the Doppler system to form Doppler beam pairs. The axis of the auxiliary beam is slightly offset from the axis of the main beam and is positioned so that the two axes are in the same vertical plane. After slant range compensation, the amplitudes of the Doppler spectrum of each beam is averaged over a predetermined time interval. The difference between the mean amplitudes of the two beams is divided by the offset angle to establish an amplitude per degree correction factor which is applied to the main beam signal returns to establish a main beam amplitude corrected Doppler spectrum.