The use of a full-order Kalman filter for the alignment process of an
inertial navigation system (INS) imposes an unacceptable burden on com
puters. In this paper we intend to design and analyze a low-order Kalm
an filter for the initial alignment of a ring laser gyro strapdown ine
rtial system that results in a substantially lighter computer burden w
ith a little significant reduction in system accuracy.