The heading error observability of the integrated system of low-cost strapdown inertial navigation system（SINS） and global positioning system（GPS） is very poor under the moving condition of stillness or uniform rectilinear.To improve the heading precision

magnetometer was added into the low-cost SINS/GPS integrated system.The complete model of integrated navigation system was derived and

simulations were implemented.The results demonstrate that the heading error of SINS/GPS integrated system diverges under the moving conditions of stillness and uniform rectilinear motion since the precision of inertial instruments are poor

while the heading error of SINS/GPS/Magnetometer integrated system converges efficiently.To validate the utility of the method in a true application

a static experiment was done.The result demonstrate that the heading error converges efficiently even the sensor precision is poor

the standard deviation of attitude error is less than 0.2° after convergence.The efficiency of the method is proved by the static experiment.