A Filtering Algorithm on Ionospheric Delay Calculation in Multi-Constellation Satellite Navigation Systems

摘要

With the development of Global Navigation SatelliternSystem (GNSS), more and more Satellite-BasedrnAugmentation Systems (SBAS) are under trial andrndevelopment. The objective of SBAS is to augmentrnGlobal Position System (GPS) by way of improving itsrnaccuracy, integrity, continuity and availability in order tornsatisfy civil aviation requirements for navigation andrnlanding. For single frequency users, ionospheric delayrnuncertainty creates the largest restriction to the accuracyrnand availability of satellite navigation. With the signalsrnfrom SBAS, it is able to directly estimate the ionosphericrndelay of single frequency users at any point in the servicernvolume, but its accuracy and integrity need to bernimproved.rnThe next generation GNSS would include GPS,rnGLONASS, Galileo and Compass satellites, the minimumrnnumber of visible satellites would be over two dozen. Itrnhas agreed that the use of two or more space-basedrnnavigation systems should provide better service than canrnbe achieved by relying solely on any one system, thusrninvestigation on interoperability of signals from thesernsystems to get better performance is of significance.rnTherefore in this paper, we will discuss on how torncalculate ionospheric delay of single frequency users inrnSBAS when multi-constellation navigation satelliternsystems are available. Specially, in Compass system, thernIPPs are motionless, and the Kalman filter is more andrnmore widely used in navigation, the filtering algorithm isrnproposed to be used in ionospheric delay calculation atrnIonospheric Grid Point (IGP). Furthermore, the analyzedrnresults will be shown afterward. Due to this method inrnSBAS, it could save the hardware consumption, as well asrnget a certain performance enhancement.rnFive sections are included in the paper. In section 1, werngive the background information about SBAS and itsrnionospheric delay correction theory. The planar fit methodrnwhich is widely used in SBAS is presented in details inrnsection 2. In section 3, we propose the Kalman Filteringrnmethod in ionospheric delay calculation at IGPs. Detailedrndescription of simulation condition, test and analysis arernshown in section 4. Section 5 is the conclusion and thernpotential problems we will go on study.