Research on Accelerating Single-Frequency Precise Point Positioning Convergence with Atmospheric Constraint

Abstract

An increasing number of researchers have conducted in-depth research on the advantages of low-cost single-frequency (SF) receivers, which can effectively use ionospheric information when compared to dual-frequency ionospheric-free combination. However, SF observations are bound to increase the unknown parameters and prolong the convergence time. It is desirable if the convergence time can be reduced by external information constraints, for example atmospheric constraints, which include ionosphere-or troposphere constraints. In this study, ionospheric delay constraints, tropospheric delay constraints, and their dual constraints were considered. Additionally, a total of 18,720 test experiments were performed. First, the nearest-neighbor extrapolation (NENE), bilinear-(BILI), bicubic-(BICU), and Junkins weighted-interpolation (JUNK) method of Global Ionospheric Map (GIM) grid products were analyzed. The statistically verified BILI in the percentage of convergence time, average convergence time, and computation time consumption of them shows a good advantage. Next, the influences of global troposphere-and ionosphere-constrained on the convergence time of SF Precise Point Positioning (PPP) were analyzed. It is verified that the ionosphere-constrained (TIC2) has significant influence on the convergence time in the horizontal and vertical components, while the troposphere-constrained (TIC1) has better effect on the convergence time in the vertical components within some thresholds. Of course, the dual constraint (TIC3) has the shortest average convergence time, which is at least 46.5% shorter in static mode and 5.4% in kinematic mode than standard SF PPP (TIC0).for instance, determines the precise orbit, surface ice flow speed, as well as positioning, navigation and timing (PNT) applications [2][3][4]. The traditional PPP models are based on Ionosphere-Free (IF) combinations with dual-frequency raw phase and code observations for the removal of the first-order effect of ionospheric refraction [5]. However, the second-and third-order ionospheric effects still exist and they may cause measurements errors of sub-centimeters in GPS [6,7]. Therefore, traditional PPP technology based on IF combinations cannot obtain ionospheric information, and the ionospheric error is not completely eliminated. In the last few years, PPP used raw observations has received an increasing amount of research attention because of its several advantages as compared to traditional IF PPP, particularly the development of new multi-frequency GNSS [8].The ionosphere refers to the atmospheric space starting at 60 km above the ground and extending to the magnetosphere. The Global Navigation Satellite System (GNSS) signal will generate ionospheric delay after passing through the ionosphere. A large number of models are currently being used to describe the delay that the ionosphere produces for electromagnetic signals propagating from satellites to receivers. If the delay is not corrected, it can have an important impact on the positioning accuracy of GNS...

Regiomontan: A Regional High Precision Ionosphere Delay Model and Its Application in Precise Point Positioning

“…The value of the mapping function is calculated according to Equation ( 6) and the latitude and longitude for the IPP are calculated. Afterwards, the VTEC is interpolated in space and time utilizing the "consecutive rotated maps" algorithm [34], which performs best in [26]. Then, the ionospheric delay is calculated with Equation (1).…”

“…Therefore, constraining the ionosphere with so-called ionospheric pseudo-observations has proven as the most promising approach [22,24]. In addition, tropospheric constraints have proven their usefulness in [25,26] alone or in addition to the ionospheric constraint ("atmospheric constraint"). The weighting of the ionospheric pseudo-observations has proven to have a direct influence on the coordinate convergence time [25].…”

The Impact of Different Mapping Function Models and Meteorological Parameter Calculation Methods on the Calculation Results of Single-Frequency Precise Point Positioning with Increased Tropospheric Gradient

“…e undifferenced and uncombined GNSS PPP model uses pseudorange and carrier phase observations, with the following expression [19,20]:…”