Abstract
The single-frequency precise point positioning (PPP) technique has attracted increasing attention due to its high accuracy and low cost. However, a very long convergence time, normally a few hours, is required in order to achieve a positioning accuracy level of a few centimeters. In this study, an approach is proposed to accelerate the single-frequency PPP convergence by combining quad-constellation global navigation satellite system (GNSS) and global ionospheric map (GIM) data. In this proposed approach, the GPS, GLONASS, BeiDou, and Galileo observations are directly used in an uncombined observation model and as a result the ionospheric and hardware delay (IHD) can be estimated together as a single unknown parameter. The IHD values acquired from the GIM product and the multi-GNSS differential code bias (DCB) product are then utilized as pseudo-observables of the IHD parameter in the observation model. A time varying weight scheme has also been proposed for the pseudo-observables to gradually decrease its contribution to the position solutions during the convergence period. To evaluate the proposed approach, datasets from twelve Multi-GNSS Experiment (MGEX) stations on seven consecutive days are processed and analyzed. The numerical results indicate that the single-frequency PPP with quad-constellation GNSS and GIM data are able to reduce the convergence time by 56%, 47%, 41% in the east, north, and up directions compared to the GPS-only single-frequency PPP.
Highlights
Precise point positioning (PPP) is a single-receiver absolute positioning technique that uses un-differenced pseudorange and carrier phase observations along with precise satellite orbit and clock products [1]
Quad-constellation observation datasets collected from 12 globally-distributed Multi-GNSS Experiment (MGEX) stations, as well as the CODE global ionospheric map (GIM) products and the Deutsches Zentrum für Luft- und Raumfahrt (DLR) multi-global navigation satellite system (GNSS) differential code bias (DCB) products on 4–10 September 2016 are used to assess the performance of the proposed single-frequency PPP approach
Since the precise coordinates of most stations are not available, their coordinate values are computed at the precise millimeter level through an Online Positioning User Service (OPUS) that is developed by as well as the CODE GIM products and the DLR multi-GNSS DCB products on 4–10 September 2016 are used to assess the performance of the proposed single-frequency PPP approach
Summary
Precise point positioning (PPP) is a single-receiver absolute positioning technique that uses un-differenced pseudorange and carrier phase observations along with precise satellite orbit and clock products [1]. The second method is to form an ionosphere-free combined observable between the code and carrier phase observations on a single frequency, which is known as GRoup And PHase Ionospheric Correction (GRAPHIC) [11,12,13,14] Based on this GRAPHIC method, an accuracy of several centimeters is achievable, but a long convergence time of over two hours is required [7]. The GRAPHIC combination from single-frequency code and phase observations produces a rank-deficient mathematical problem [15] Both methods suffer major limitations where the first method converges more quickly, but can only achieve decimeter-level positioning accuracy while the second method can achieve centimeter-level positioning accuracy, but requires a very long convergence time. The converging performance of the proposed single-frequency PPP approach is assessed
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call