Technique Research Of Integrity Monitoring On BDSBAS

GNSS is of great importance to the economic and military fields in the current world,so the world powers build their own GNSS one after another.ICAO puts forward a concept of Required Navigation Performance(RNP)which contains four aspects of accuracy,integrity,continuity and availability to meet the need of civil aviation.The world powers come to develop their SBAS to satisfy the performance,aiming to provide service of higher accuracy and integrity for the users of wide area.With the development of BDS,it is necessary to develop our own SBAS to provide service of high quality for the civil aviation users in China and the surrounding area.First of all,the paper gives an introduction of BDS and its coordinate system and time system.Then the BDS navigation message file and observation date file of RINEX are explained.The algorithm of calculating the satellite's coordinate by utilizing the ephemeris parameters is also given.Then the paper elaborates the principle of SBAS and describes the data processing.The error processing algorithms are emphasized,which contains ionospheric delay algorithm,tropospheric delay algorithm,satellite clock error and ephemeris error.The paper gives a comparison of grid ionospheric model and Klobuchar model,and proves the correction result of grid ionospheric model is much better.Finally the integrity monitoring technique of BDSBAS is introduced.The paper gives an explanation of how to calculate integrity parameters,such as UDRE,RURA and GIVE.Then the paper makes a simulation analysis by utilizing the observation data provided by Cmonoc.The results proves that the error of UDRE and RURA can be applied during airway,final and approach phase,but the analysis result of GIVE is not ideal,for the reason that the number of reference stations is small,so the grid ionospheric model is not accurate.