Abstract
Precise Point Positioning (PPP) has become a very hot topic in GNSS research and applications. However, it usually takes about several tens of minutes in order to obtain positions with better than 10 cm accuracy. This prevents PPP from being widely used in real-time kinematic positioning services, therefore, a large effort has been made to tackle the convergence problem. One of the recent approaches is the ionospheric delay constrained precise point positioning (IC-PPP) that uses the spatial and temporal characteristics of ionospheric delays and also delays from an a priori model. In this paper, the impact of the quality of ionospheric models on the convergence of IC-PPP is evaluated using the IGS global ionospheric map (GIM) updated every two hours and a regional satellite-specific correction model. Furthermore, the effect of the receiver differential code bias (DCB) is investigated by comparing the convergence time for IC-PPP with and without estimation of the DCB parameter. From the result of processing a large amount of data, on the one hand, the quality of the a priori ionosphere delays plays a very important role in IC-PPP convergence. Generally, regional dense GNSS networks can provide more precise ionosphere delays than GIM and can consequently reduce the convergence time. On the other hand, ignoring the receiver DCB may considerably extend its convergence, and the larger the DCB, the longer the convergence time. Estimating receiver DCB in IC-PPP is a proper way to overcome this problem. Therefore, current IC-PPP should be enhanced by estimating receiver DCB and employing regional satellite-specific ionospheric correction models in order to speed up its convergence for more practical applications.
Highlights
Precise Point Positioning (PPP) was firstly proposed by Zumberge et al [1] and a position accuracy of about 2 cm was demonstrated by the Jet Propulsion Laboratory (JPL) with daily dual-frequency data at a single station using precisely estimated satellite orbits and clocks and Earth rotation parameters [1].(IGS) [2]
We investigate the impact of the accuracy of ionospheric delay correction models on PPP performance
In order to evaluate the impact of the quality of ionospheric delay corrections and the receiver differential code bias (DCB), three PPP modes are employed in the experimental test: PPP using ionosphere-free observations (LC-PPP), PPP using raw observations with ionospheric delay constraints, i.e., ionospheric delays constrained PPP (IC-PPP), and the ionospheric delay constrained precise point positioning (IC-PPP) with receiver DCB parameter (IC-PPP + DCB)
Summary
Precise Point Positioning (PPP) was firstly proposed by Zumberge et al [1] and a position accuracy of about 2 cm was demonstrated by the Jet Propulsion Laboratory (JPL) with daily dual-frequency data at a single station using precisely estimated satellite orbits and clocks and Earth rotation parameters [1]. To improve its accuracy and to shorten the convergence time, approaches for PPP ambiguity resolution were developed by estimating the Un-calibrated Phase Delay (UPD) (Ge et al [12]) or mitigating the UPD into satellite clocks (Laurichesse and Mercier [13]; Colinns et al [14]). Li et al proposed PPP using raw GNSS observations with ionospheric parameters with aforementioned constrained and confirmed its improvement on PPP performance in terms of both accuracy and convergence [15] In this contribution, we investigate the impact of the accuracy of ionospheric delay correction models on PPP performance.
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