Research on improvement of position accuracy for satellite navigation

摘要

Some deficiencies of the system of exciting satellite navigation augmentation are analyzed in the application of civil aviation. Since there is no local monitoring in Wide Area Augmentation System (WAAS), the protect level is increased, and the availability is reduced, so it could not satisfy the requirement of the precise approach. Moreover, because the Local Area Augmentation System (LAAS) could not solve the problem brought by ionosphere storms, the LAAS certification becomes complex and expensive. The basic principle of the new satellite navigation augmentation system named Local Airport Monitor (LAM) proposed by Federal Aviation Administration (FAA) is introduced. And the error distribution characteristic of LAM is discussed by sorting three conditions. Moreover, the expressions of LAM protection level and availability are studied. Some conclusions are obtained by simulations. In normal condition, the position accuracy of LAM is better than the one of WAAS and similar to LAAS and the availability of LAM is better than the one of WAAS and worse than LAAS. When there are ionosphere storms, the position precision and availability of LAM and WAAS reduce a little, but the position precision and availability of LAAS reduce 20.5% and 19.3% respectively. Furthermore, the availability of LAM is analyzed and simulated. And some conclusions are obtained: airborne user should first choose satellites whose elevation is lower than 10 degree and bigger than 70 degree. Reference station and airborne should use GAD-A and AAD-B receiver respectively, thus, the availability of LAM could bigger than 99.99%