Compared with the traditional platform gyro compass

the fiber strapdown gyrocompass have advantages of well maintain and high reliability and so on.A strapdown gyrocompass algorithm that can be used in fiber strapdown gyrocompass system

which is different from the traditional platform compass algorithm is designed.The algorithm introduces a new inertial coordinate system

which the rotation of the geography coordinate systerm can be calculated by putting the gravity projection on

and the rotation of the carrier coordinate system can be calculated by using gyro outputs

the attitude of the carrier can be calculated.To get method of gravity projection of the inertial coordinate system using FIR digital filter.At last

simulation demonstrates that the algorithm and the theory are correct.