Assessment of ionospheric corrections for PPP-RTK using regional ionosphere modelling

D Psychas,H Visser,S Verhagen,X Liu,Y Memarzadeh

doi:10.1088/1361-6501/aaefe5

D Psychas, H Visser + Show 3 more

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https://doi.org/10.1088/1361-6501/aaefe5

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Abstract

This paper presents an analysis of the ionospheric corrections required to get a significant improvement in PPP-RTK performance. The main aim was to determine the improvement in the position precision and time-to-first-fix in the PPP-RTK user side using ionospheric corrections computed from a network. The study consists of two main steps. The first one includes an empirical investigation of the ionosphere model precision necessary to greatly improve the PPP-RTK performance in a simulated environment in terms of precision and convergence time. In the second one, an optimal ionosphere representation was developed to provide precise ionospheric corrections by parameterizing the ionospheric slant delays after the PPP-RTK network processing in terms of ionosphere model coefficients and differential code biases using real GNSS measurements. Experimental results demonstrate that the proposed methodology can be used for reliable regional ionosphere modeling and satellite code bias estimation, due to the consistency of the satellite code bias estimates with those provided from the International GNSS Service Analysis Centres, the high stability of the estimated receiver and satellite code biases and the low least-squares residuals of the network-based ionosphere modeling solution. Finally, it has been shown that the precision of ionospheric corrections at zenith needs to be better than 5 cm to enable faster PPP-RTK solutions.

Highlights

The integer ambiguity resolution (IAR) enabled precise point positioning (PPP) method, the so-called PPP-RTK (Wubbena et al 2005), is a state-of-the-art global navigation satellite systems (GNSS) technique that allows to determine high-accuracy positions with short convergence time
This paper presents an analysis of the ionospheric corrections required to get a significant improvement in PPP-RTK performance
A design computation is performed in this study, simulating a GPS-only dual-frequency PPP-RTK user environment in order to assess the effect of the ionospheric corrections precision on the time-to-first-fix (TTFF), instead of the convergence time since no real data are used in this case

Summary

Introduction

The integer ambiguity resolution (IAR) enabled precise point positioning (PPP) method, the so-called PPP-RTK (Wubbena et al 2005), is a state-of-the-art global navigation satellite systems (GNSS) technique that allows to determine high-accuracy positions with short convergence time. The main idea behind PPP-RTK is to extend the PPP technique (Zumberge et al 1997) by providing single-receiver users, apart from precise orbits and clocks, with additional corrections (satellite phase biases, ionospheric and tropospheric corrections) so as to enable IAR with fast or even instantaneous convergence to the centimeter level. A single-receiver PPP user who uses ionosphere-free (IF) carrier-phase and code observations, along with precise satellite orbit and clock products provided by the International GNSS Service (IGS) (Dow et al 2009), can achieve an acc uracy on the order of a few centimeters and of a few decimeters within one hour using GPS-only data in static and kinematic modes, respectively (Bisnath and Gao 2009, Banville et al 2014). In relative positioning techniques, such as with real-time-kinematic (RTK), these biases are eliminated with double-differenced measurements and, as such, the double-differenced ambiguities can be fixed to their integers

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