Tilt Monitoring of Building Structural Safety Based on BDS-3 Single-Epoch Positioning Algorithm

The BeiDou-3 Navigation Satellite System (BDS-3) broadcasts multi-frequency signals, including B1C, B2a, B1I, and B3I, offering a new technical approach for tilt monitoring of building structural safety. However, in building structural safety tilt monitoring based on the BDS-3 single-epoch algorithm, the engineering performance differences between the B1C/B2a new signal combination and the B1I/B3I traditional signal combination—in terms of monitoring accuracy, ambiguity fixing rate, computational efficiency, and tilt rate—have yet to be fully validated through comparative analysis. To address this issue, this paper proposes a building structural safety tilt monitoring method based on the BDS-3 single-epoch algorithm and conducts a field test on a multi-story building in Beijing. First, a BDS-3-based kinematic monitoring model is established, and an integer ambiguity error search band method based on the main and auxiliary frequencies is proposed. On this basis, three schemes are designed using medium Earth orbit (MEO), inclined geosynchronous orbit (IGSO), and geostationary Earth orbit (GEO) satellites, B1C/B2a (MEO/IGSO), B1I/B3I (MEO/IGSO), and B1I/B3I (MEO/IGSO/GEO), to comparatively analyze the accuracy, ambiguity fixing rate, computational efficiency, and measured tilt results of each scheme in building structural safety tilt monitoring. Experimental results show that all three schemes based on the BDS-3 single-epoch algorithm achieve millimeter-level monitoring accuracy and an ambiguity fixing rate exceeding 99%, with average computational times of 0.351 s, 0.338 s, and 4.572 s and corresponding building tilt rates of 0.22‰, 0.20‰, and 0.18‰, respectively, yielding an average tilt rate of 0.20‰. These results satisfy the 4‰ limit specified in the Code for Deformation Measurement of Building and Structure (JGJ 8-2016), thereby confirming the feasibility and effectiveness of the proposed method and offering a novel BDS-3 single-epoch algorithm for building tilt monitoring.