Ensuring High Integrity of GNSS Precise Orbit and Clock Products Based on Performance-Assured Sliding-Window Innovation Test

Abstract

Precise Point Positioning – Real-Time Kinematic (PPP-RTK) can offer fast and accurate positioning services by employing raw measurements from Global Navigation Satellite Systems (GNSS) along with precise satellite orbit, clock, bias, and atmospheric products. Incorrect orbit and clock products may threaten the generation of satellite bias and atmospheric products, leading to hazardously misleading information at the user end. Therefore, their integrity monitoring is of great importance for achieving safety-assured PPP-RTK. There had been a few studies focusing on fault detection of precise orbit and clock products. However, they paid little attention to theoretically quantify the integrity performance of the detectors, thereby being unable to provide reliable integrity support message and be applied in Protection Level (PL) calculation. In response, a dedicated sliding-window innovation-based integrity monitoring detector is designed for precise orbit and clock products, whose integrity performance can be guaranteed. To achieve this, innovation-based test statistics utilized in this paper is constructed step by step from raw measurement equations. After analyzing the drawback of performance degradation using snapshot-based detection method, the sliding-window innovation-based detector is designed to detect the faults in orbit and clock products, with a special focus on small ramp errors. Then, the theoretical performance of the designed detector considering the requirement of integrity is analytically derived. The theoretical optimal window length is also analyzed. Simulations are carried out for performance verification. Comparing to snapshot-based method, sliding window method has better performance on ramp fault detection, even with very short window length.