In order to get the accuracy of short-time navigation of strap-down inertial navigation system (SINS)

navigation error mathematic model is established

and the effect of inertial devices error on navigation accuracy of system is analyzed. With strap-down inertial navigation mechanism

aiming at the characteristic of short-time navigation

navigation equation of carrier in navigation coordinate is predigested. Attitude error of carrier is deduced by installation error of inertial devices and equivalent zero-shift of gyroscopes. Combing with navigation equation

attitude error equation and error of inertial devices

mathematic model of velocity error and position error is derived. Based on the error mathematic model

state-space model and block diagram of error model are established. Module of error model

which is combined with strap-down inertial navigation algorithm to calculate navigation data in ground within 150s

is built in Matlab/Simulink. The experimental results show that relative system error of x-axes of navigation coordinate is less than 20%

and that of y-axes and z-axes is less than 5%

respectively. Simulation results also show that the change of accelerometer accuracy influences the SINS navigation error basically.