An Improved Long-Period Precise Time-Relative Positioning Method Based on RTS Data

Area of Science:

• Geodesy and Geomatics
• Satellite Navigation Systems
• Signal Processing

Background:

• Traditional high-precision positioning methods like Real-Time Kinematic (RTK) and Precise Point Positioning (PPP) have limitations, including reliance on reference stations or long initialization times.
• Existing time-relative positioning methods suffer from increased errors over time and sensitivity to initial positioning errors.
• Global Navigation Satellite System (GNSS) measurements are prone to time-varying errors affecting long-period positioning accuracy.

Purpose of the Study:

• To develop an improved time-relative positioning algorithm that overcomes the limitations of existing methods for long-period, high-precision positioning.
• To enhance the accuracy and robustness of single-receiver precise positioning using GNSS data.
• To provide a reliable method for achieving centimeter-level positioning accuracy over extended durations.

Main Methods:

• An improved time-relative positioning algorithm is proposed, utilizing a Precise Point Positioning (PPP) model to estimate current epoch parameters, including float ionosphere-free ambiguities.
• Estimated float ambiguities from the current epoch are used as constraints for the base epoch estimation via a robust Kalman filter.
• Positioning is achieved by differencing position vectors between the current and base epochs, using a single dual-frequency (L1/L2) satellite receiver.

Main Results:

• The proposed algorithm achieves centimeter-level positioning accuracy over a one-hour period in both static and dynamic tests.
• Combining multiple GNSS constellations (GPS, BeiDou, Galileo) significantly improves positioning accuracy due to increased satellite visibility and better geometric distribution.
• The positioning accuracy is demonstrated to be independent of initial positioning errors, unlike traditional time-relative methods.

Conclusions:

• The improved time-relative positioning method offers a robust solution for long-period, high-precision positioning using a single GNSS receiver.
• The algorithm effectively mitigates the impact of time-varying errors and initial positioning inaccuracies.
• This method enhances the practical application of precise positioning in scenarios where traditional techniques are less suitable.