Abstract: The invention relates to an apparatus for compensating the output of a pendulous induction compass transmitter to eliminate heading errors during turns due to the vertical component of the Earth's magnetic field as well as those due to the horizontal component of the Earth's magnetic field perpendicular to the axis of tilt. By compensating for the effects of the Earth's vertical field component, instabilities and anomalies such as "Northerly Turning Error" are eliminated or minimized. Compensation for vertical field error is provided by generating a signal proportional to the product of the Earth's magnetic field M, the sine of the magnetic dip angle D at the given latitude and the sine of the aircraft tilt or bank angle .phi.. A compensating signal proportional to cos .phi. is generated and used to compensate for two cycle error.

Abstract: The invention relates to an apparatus for compensating a "strapdown" induction compass transmitter to eliminate heading errors during turns, and during climbing and diving maneuvers which are due to the vertical component of the Earth's magnetic field as well as those due to the horizontal component of the Earth's magnetic field perpendicular to the axis of tilt. Instabilities and anomalies such as "Northerly Turning Error" which are due to the vertical field are thus eliminated or minimized as is two cycle error which is due to the Earth's horizontal field during these same maneuvers. The vertical field compensating signal during turns is proportional to the product of the Earth's magnetic field, M the sine of the dip angle D and the sine of the bank or roll angle .phi.. The vertical field pitch compensating signal while climbing or diving is proportional to the product of the sine of the pitch angle .theta., the Earth's magnetic field M and the sine of the magnetic dip angle D.