Abstract
The European Global Navigation Satellite System Galileo is gradually deploying its constellation. In order to provide reliable navigation and position services, the effectiveness and reliability of ambiguity resolution between reference stations is necessary in network real-time kinematic (NRTK). The multifrequency signal of Galileo could much enhance the ambiguity resolution (AR) reliability and robustness. In this study, to exploit full advantage of this, the geometry-free (GF) TCAR and ionospheric-free (IF) triple-carrier ambiguity resolution (TCAR) methods were utilized in solving the ambiguity in the Hong Kong area, which is an ionosphere disturbance active area, and compared with each other. The IF TCAR method was then used to combine multi-systems to improve Galileo E1 AR performance, which is named as the combined IF (CIF) TCAR method. Three experiments were carried out in the Hong Kong area and the results showed that the Galileo-only system could fix ambiguities on all satellite pairs correctly and reliably by the IF TCAR method, while the GF TCAR method showed a weaker performance. The wide-lane (WL) convergence time of the IF TCAR method is improved by about 37.6%. The IF TCAR method with respect to the GF TCAR method could improve the WL accuracy by 21.6% and the E1 accuracy by 72.7%, respectively. Compared with GPS-only TCAR or Galileo-only TCAR, the ambiguity accuracy and the convergence time of the CIF TCAR method, which combines GPS and Galileo, could be improved by about 25.7% and 47.1%, respectively.
Highlights
Galileo has been under development by the European Union (EU) since 1999 with the objective of providing a free, open and independent high-precision positioning system for civil users
The full constellation of the Galileo system is expected to consist of 30 active in-orbit satellites by 2020, with the signals transmitted on three frequency bands, i.e., E1 (1575.42 MHz), E5 (1191.795 MHz) and E6 (1278.75 MHz), and the E5 band consists of E5a (1176.45 MHz) and E5b (1207.14 MHz), which signals could be used either separately
5, we find that both the methods could fix ambiguity of the improved by compared with the Full Operational Capability (FOC) satellite pairs correctly with a smooth processing, but the IF triple-carrier ambiguity resolution (TCAR) method is more
Summary
Galileo has been under development by the European Union (EU) since 1999 with the objective of providing a free, open and independent high-precision positioning system for civil users. Two Galileo in-orbit validation element (GIOVE) satellites were launched in. 2005 [1] and 2008, respectively, followed by the launch of four In-Orbit Validation (IOV). Satellites in 2011 and 2012 to validate the signals and system [2]. The launch of the Full Operational Capability (FOC) satellites started from 2014 [3], and to this day, there are 20 Galileo FOC satellites providing positioning service to the global users and two FOC satellites suffered from orbit injection failure [4,5]. The E6 signal is encrypted for commercial use and cannot be tracked by the receivers in open data source [6]
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