Aiming at the problem that the measurement precision of roll angle decreases when pitch angle changes during the application of two-axis magnetic sensor in measurement of the roll angle of projectile body

an improved method for measurement of roll angle of the projectile body with the two-axis magnetic sensor is proposed.Based on the assumption that the geomagnetic field modulus is constant during the short-range flight of the projectile body

this method uses information of geomagnetic field sensor and geomagnetic field modulus in radial direction of projectile body to calculate axial geomagnetic field component reflecting the projectile body’s pitching information

and achieves the accurate acquisition of roll angle under the condition of the variation of pitching angle.Due to the existence of interference magnetic field of the projectile in the actual flight

error exists in the obtained geomagnetic field information of the third axis

which further leads to errors in pitch angle and roll angle.The error propagation model between measuring error of pitch angle and measuring error of roll angle is established. Simulation and semi-physical experiments show that the RMS measurement error of roll angle is less than 1° in the range of pitch angle variation（-45°

45°）

and the precision is 8.8 times higher than that of the traditional method.