The effect of the gyro nonorthogonality on the two-step gyrocompassing process is analyzed. It is shown that the azimuth misalignment resulting from gyro nonorthogonality depends on the platform direction with respect to geographic frame. Gyrocompassing error is explicitly expressed in terms of gyro nonorthogonality and gyro parameters. A compensation scheme to eliminate the gyrocompassing error, which results from gyro nonorthogonality, is presented. This method can be used in cases where the gyro nonorthogonality error is beyond the standard requirements for high quality platforms. The main advantage is that it allows an increase in the tolerance of gyro nonorthogonality, and reduces the cost of inertial measurement unit manufacture.
