Evaluation And Research On WAAS Performance

As a high-end customers of satellite navigation,civil aviation has extremely high requirements on the performance of the navigation system.In order to meet the urgent needs of civil aviation for the performance of satellite navigation systems,the Satellite Based Augmentation Systems(SBAS)was established by the corresponding countries and regions to comprehensively enhance the Required Navigation Performance(RNP)of the Global Positioning System(GPS)and the Global Navigation Satellite System(GLONASS).SBAS performance evaluation research will be an important part of system certification,testing and performance analysis.Wide Area Augmentation System(WAAS)as one of the most mature SBAS at present,plays a leading role in technology.Based on research of the operating principles of WAAS,combines the relevant standards of the International Civil Aviation Organization(ICAO)and the performance reports of other mature international SBAS to conduct a comprehensive and in-depth research on the accuracy,integrity,continuity and availability of WAAS.Establish a WAAS performance evaluation system,the evaluation methods and evaluation procedures for these four performance parameters are given.The main work of this paper is as follows:1)Based on the research of WAAS message structure and message content,the WAAS message decoding system is designed to extract message parameters.Combined with the extracted message parameters,the correction algorithms for ephemeris error,satellite clock error,tropospheric error and ionospheric error are given.2)Analyze the similarities and differences between the Geostationary Earth Orbit(GEO)satellite and GPS satellite position correction and clock correction.The GEO satellite is included in the navigation and positioning calculation,and the calculation method and calculation process of the positioning error and the protection level are given.Based on the measured data of WAAS monitoring station,the influence of the number of GEO satellites on WAAS message delay,message interruption,positioning error and protection level is researched.3)Based on the Signal In Space(SIS)performance requirements and WAAS performance analysis report,a WAAS performance evaluation system is established.Combining the solution process of the positioning error and the protection level,the service level that can be satisfied by the accuracy and integrity of the monitoring station location are given;on the basis of achieving the enhancement of accuracy and integrity,the service level that can be satisfied by the continuity and availability of WAAS is evaluated,the evaluation method and evaluation process of each performance index are given.4)Combine WAAS and Localizer Performance with Vertical guidance(LPV)approach and evaluate WAAS approach performance.First,according to the 7L runway chart of Anchorage International Airport,the aircraft flight trajectory during the approach is generated,and then the calculation process of the accuracy and integrity parameters of WAAS in the approach process is given.Finally,the 7L runway of Anchorage International Airport is taken as an example,the accuracy and integrity parameters of WAAS during the approach were evaluated.5)In order to further explore the connotation of integrity,on the basis of analyzing the implementation of the Galileo satellite navigation system(Galileo)and WAAS integrity monitoring,the relationship between WAAS integrity risk,K factor and protection level is derived.The distribution method of WAAS integrity risk is researched.Based on the assumption of integrity risk distribution,the distribution characteristics of east,north,and up errors are verified,and the K factor is obtained from the error distribution characteristics and integrity risk.