Abstract: The improved direction finder of the instant invention has three orthogonal antenna elements or an array of antenna elements consisting of antennas in three dimensions. Amplitude and phase difference measurements are made on various combinations of antennas, and they are compared to a data base of antenna relationships that correspond to three dimensional angles. The spacial angle of arrival of electromagnetic signals are determined by the fit between the measured parameters and the stored relationships. This apparent direction of arrival is compensated for any motion of the antenna by an error signal representative of antenna motion with respect to inertial space. The apparent direction of arrival is thereby compensated to provide true direction of arrival determinations. The motion compensated direction finding system of the invention has especial utility for buoys released from undersea vessels released to sea surface.