Innovative Atmosphere Effect Mitigation Using New GNSS Signals
【摘要】：正New signals from the modernised satellite navigation systems(GPS and GLONASS) and the developing systems(COMPASS and GALILEO) will present opportunities for more accurate and reliable positioning solutions.Successful exploitation of these new signals will also enable the development of markets and applications for difficult environments,which may not suit the current Global Navigation Satellite System (GNSS) systems.The research presented in this paper is aiming to exploit the improvement in monitoring, modelling and mitigating the atmospheric effects,with the appearance of the new signals and satellites.The results will provide a potential supplement to high accuracy positioning techniques,such as RTK and PPP Both the troposphere and ionosphere effects are studied in this work.In terms of the troposphere effect,it is mitigated/solved in RTK and PPP via different approaches.Neither of these methods takes the horizontal distribution of troposphere delay into consideration,this is mainly due to the high temporal and spatial variability of water vapour in the troposphere,which is difficult to interpolate or model accurately.With increased number of satellites observable,a better investigation of the troposphere wet delay horizontal distribution could be attempted. If the measurements from a network of CORS stations are dense enough,a near real time horizontal troposphere delay correction for the network area could be produced.It could then be used as a supplement to either the interpolation procedure in Network RTK or the mapping function procedure in PPP,improving both the accuracy and the convergence time.The preliminary generation algorithm of this horizontal troposphere delay correction is introduced in this paper. As for the ionospheric effects,the GNSS modernization provides an opportunity to study the higher(second and third) order ionospheric range errors and scintillation effects(abrupt power fades and phase variations in received signals).The way the new signal properties(higher chipping rates,longer codes,multi-frequencies,data-free signal components) can be used to improve/contribute to both ionosphere delay and scintillation models currently available is investigated.The Spirent GSS800 GNSS simulator is used to perform multi-frequency simulations with different ionospheric electron content profiles.For the scintillation effects,receiver signal tracking performance is evaluated by the phase and code tracking loop errors.The existing scintillation sensitive tracking models,such as the ones developed by Conker et al,are used for this evaluation.Effort is being made in order to improve these models which are limited to weak-to-moderate scintillation levels and/or to devise methods to characterise receiver performance during weak-to-strong levels of scintillation.Scintillation-oriented simulations are performed using the Cornell Scintillation Model and by considering various receiver and scintillation parameters.As a preliminary approach to investigate the effect of scintillation on the(code-based) range measurements,UERE on a receiver-satellite link is also investigated. The above research is part of the project Innovative Navigation using new GNSS SIGnals with Hybridized Technologies(iNsight),which is funded by the UK Engineering and Physical Sciences Research Council(EPSRC) and carried out by the four leading UK GNSS universities in collaboration with nine commercial companies and government agencies:Air Semiconductors,Civil Aviation Authority,EADS Astrium,Leica Geosystems, Nottingham Scientific Limited,Ordnance Survey,QinetiQ,ST Microsystems,and Thales Research and Technology.