Toward global instantaneous decimeter-level positioning using tightly coupled multi-constellation and multi-frequency GNSS

Abstract

Autonomous driving represents one of the emerging applications that require both high-precision positions and highly critical timeliness to reach stringent safety standards. We develop a method to potentially achieve global instantaneous decimeter-level positioning by virtue of tightly coupled multi-GNSS triple-frequency observations contributing to precise point positioning (PPP). Inter-system phase biases (ISPBs) for two wide-lane observables are first computed for each station to form inter-GNSS resolvable ambiguities, and then correspondingly two wide-lane fractional-cycle biases (FCBs) are computed for each satellite to recover the integer property of single-station ambiguities. With both ISPB and FCB products, we can accomplish tightly coupled multi-GNSS PPP wide-lane ambiguity resolution (PPP-WAR) using only a single epoch of triple-frequency observations on a global scale. To verify this method, we used 1 month of GPS/BeiDou/Galileo/QZSS data from 107 globally distributed stations and 1 h of such multi-GNSS data collected on a vehicle moving in an urban area. We found that both ISPB and FCB products could be estimated every 24 h with high precisions of around or below 0.1 cycles; 83-98% of their day-today variations fell within 0.1 cycles, facilitating their precise predictions for real-time applications. Using these corrections, we achieved both instantly and reliably ambiguity-fixed solutions at 91.2% of all epochs at the 107 stations on average; the resultant single-epoch positions reached a mean accuracy of 0.22 m, 0.18 m and 0.63 m for the east, north and up components, respectively, in case of abundant triple-frequency observations from over 15 satellites. Similarly, for the vehicle-borne test, we obtained instantaneous PPP-WAR solutions at 99.31% of all epochs and achieved a positioning accuracy of 0.29, 0.35 and 0.77 m for the east, north and up components, respectively, which improved significantly the identification of road lanes as opposed to other single-epoch solutions. Finally, we expect that the prospect of instantaneous PPP-WAR in aiding driverless vehicles can be more promising if, whenever possible, integrated with inertial sensors and/or smoothed through multi-epoch data.

A Review of Global Navigation Satellite System (GNSS)-Based Dynamic Monitoring Technologies for Structural Health Monitoring

“…A similar study was performed in Pan et al [110]. In Geng et al [111,112], a method was proposed to estimate station-specific phase biases (ISPBs). Then resolvable ambiguities between GNSSs (inter-system) instead of within GNSSs (intra-system) are formed for a more efficient partial AR.…”

Speeding up PPP ambiguity resolution using triple-frequency GPS/BeiDou/Galileo/QZSS data

“…In conclusion, (extra-)wide-lane FCBs can be predicted for real-time PPP over a long time span (e.g., hours to even days) with high precisions to ensure a high success rate of (extra-)wide-lane ambiguity resolution, while narrow-lane FCBs should be predicted with more cautions to reduce the risk of degraded PPP-AR efficiency. The fundamental idea behind rapid triple-frequency PPP-AR of this study is that, once both extra-wide-lane and wide-lane ambiguities are resolved (i.e., PPP-WAR achieved), an unambiguous ionosphere-free wide-lane carrier-phase can be obtained, no matter whether implicitly or not, which is expected to outweigh the raw pseudorange to speed up the convergences of narrow-lane ambiguities (Geng et al, 2018a). However, we should be cautious of such results, since it depends on whether such unambiguous wide-lane carrier-phase is indeed sufficiently less noisy than the raw pseudorange.…”

Assessment of Quad-Frequency Long-Baseline Positioning with BeiDou-3 and Galileo Observations

“…Even with multiple GNSSs, PPP still takes about 10 min to obtain reliable integer ambiguity resolutions. In addition, if an open sky-view is not constantly available, frequent re-convergences can destroy the practicability of real-time PPP completely [12,13].…”