Abstract:In view of the extremes of the non-integrity events of the ground based augmentation system(GBAS), we study the integrity algorithm of GBAS. We give the calculation method of airborne protection level under H0 and H1 assumptions, and analyze the influences of the main error sources of two kinds of non-integrity events, false alarm and missed alarm. We carry out verification experiments, and the experimental results show that the accuracy of the position solution of the airborne terminal after differential correction is better than 1 meter, and its availability is greater than 99.999 9%, which meets the requirements of class Ⅰ precision approach and landing navigation. At the same time, we carry out simulations of non-integrity events, and the results show that the geometric distribution of satellite and ionospheric storm are the main error sources of false and missed alarms. In the future, class Ⅲ GBAS needs to expand the single constellation to multiple constellations including Beidou, and upgrade the single frequency to dual frequency. Among them, multiple constellations can optimize the geometric layout of satellites and dual frequency can eliminate the ionospheric storm impact.