Research Of GNSS Carrier Phase Difference Location Based On Regional Ionospheric Model

The satellite navigation and positioning technology has been well developed and applied with the development of global navigation satellite system(GNSS).Satellite navigation and positioning technology with low cost,high efficiency,high precision,without time and geographical constraints of these advantages,making it a very wide range of applications,involving the global military,civil and other fields.In many satellite navigation and positioning technology,precision relative positioning technology is becoming more widely used.The key of achieved precision relative positioning technology is the system errors contained in a strong correlation at both ends to ensure that effectively weaken or even offset these Error.Atmospheric delay error,ionospheric delay,orbit error,receiver clock error can be suppressed by double difference or accurate model correction to eliminate or even eliminate.In the carrier phase difference residual error,the ionospheric error is the most significant error source of the positioning accuracy.Ionospheric delay,as the main source of error in precise relative positioning,has been a hotspot.Therefore,this paper mainly focuses on the ionospheric delay characteristics of GNSS and the application of regional ionospheric model in carrier phase differential positioning.The main works are as follows:(1)Analysis of carrier phase precision relative positioning model and the main error sources that affect positioning accuracy.The ionospheric delay is the main source of error which affects the positioning accuracy.With the increase of the baseline length,the spatial correlation is weakened and can not be eliminated by the differential technique.(2)Based on the generation principle of ionospheric delay,the commonly used ionospheric delay correction method is analyzed.The results show that the ionospheric delay is influenced by the sunspot activity,geographical position,climate and so on,and has obvious regional and time domain Differences,showing different regional and cyclical changes.The traditional ionospheric delay correction method mainly includes dual frequency correction method,ionospheric model method and differential correction method,lack of geographical and time domain balance.In this paper,it is proposed that the ionospheric delay correction can be extracted from the double difference residuals in the carrier phase difference location to construct the regional ionosphere model,which can better match the regional and temporal changes of the ionospheric delay.(3)In order to obtain a more precise ionospheric delay,a method combining combined carrier phase wide-lane and pseudorange narrow-lane combination(MW-WL)and de-ionospheric combination(IF)is proposed to solve each frequency band Integer ambiguities,combined with multi-epoch accumulation to achieve further optimization.The results of the global ambiguity resolution with high fixed rate and high accuracy can obtain the accurate ionospheric delay.(4)The regional ionospheric aided carrier phase difference localization experiment was carried out with the data of 22 km baseline length.The experimental results show that,with the help of regional ionosphere,the ambiguity fixed rate of carrier phase differential positioning is different from the traditional carrier phase difference Positioning and single-frequency multi-epoch-cumulant,respectively,compared to 75% and 30%,respectively,increased positioning accuracy of 92% and 69%.The dual-difference ionospheric delay can be extracted by MW-WL / IF combined method,which can not only improve the fixed ambiguity fixed rate of carrier phase differential positioning,but also can effectively improve the positioning accuracy.The influence of ionospheric delay correlation is weakened after the baselines are extended.