The problems associated with large initial misalignment angles for the so called gyrocompass alignment of
strapdown inertial navigation system(SINS) is considered. In this work, the analysis of gyrocompass alignment is approached
from active disturbance rejection control (ADRC) theory point of view, which is called ADRC gyrocompass alignment. Based
on Euler platform error angles nonlinear error model, the two-order state space model which is applicable to ADRC for level
loop alignment is developed. The level loop command rate obtained from the level velocity error is fed into transformation
matrix for integration driving the level misalignment angles to zero. When the system is leveled, the level command rate
for leveling the transformation matrix is in the steady state which can be used to calculate the azimuth misalignment angle.
The numerical simulation results show that the ADRC gyrocompass alignment can quickly achieve alignment independent
on initial misalignment angles but with the same accuracy as the classical gyrocompass alignment.