Assessment of high-rate GPS using a single-axis shake table

Abstract

The developments in GNSS receiver and antenna technologies, especially the increased sampling rate up to 100 sps, open up the possibility to measure high-rate earthquake ground motions with GNSS. In this paper we focus on the GPS errors in the frequency band above 1 Hz. The dominant error sources are mainly the carrier phase jitter caused by thermal noise and the stress error caused by the dynamics, e.g. antenna motions. To generate a large set of different motions, we used a single-axis shake table, where a GNSS antenna and a strong motion seismometer were mounted with a wellknown ground truth. The generated motions were recorded with three different GNSS receivers with sampling rates up to 100 sps and different receiver baseband parameters. The baseband parameters directly dictate the carrier phase jitter and the correlations between subsequent epochs. A narrow loop filter bandwidth keeps the carrier phase jitter on a low level, but has an extreme impact on the receiver response for motions above 1 Hz. The amplitudes above 3 Hz are overestimated up to 50 % or reduced by well over half. The corresponding phase errors are between 30 and 90 degrees. B S. HäberlingCompared to the GNSS receiver response, the strong motion seismometer measurements do not show any amplitude or phase variations for the frequency range from 1 to 20 Hz. Due to the large errors for dynamic GNSS measurements, it is essential to account for the baseband parameters of the GNSS receivers if high-rate GNSS is to become a valuable tool for seismic displacement measurements above 1 Hz. Fortunately, the receiver response can be corrected by an inverse filter if the baseband parameters are known.

A literature review of next-generation smart sensing technology in structural health monitoring

“…Sensors based on Global Positioning System (GPS) provided an easy‐to‐install remote nonintrusive approach to the SHM. The GPS is reasonably accurate and gives dynamic measurements of 20 Hz or more in case of high‐rate GPS . However, the GPS can be very sensitive to electromagnetic noise, environmental interference, and weather conditions.…”

Using the signal-to-noise ratio of GPS records to detect motion of structures

“…In the last decade, the potential for using the Global Positioning System (GPS) in structural health monitoring (SHM) has been revealed through experimental studies, which proved its ability in monitoring oscillations of subcentimeter level displacement and high‐rate frequencies,[] and applications to real monitoring of bridges[] and buildings or towers,[] where the GPS monitoring was successfully used to estimate the main characteristics of the structures response. Furthermore, the recent rapid developments in the GPS system, such as 100‐Hz high‐rate receivers,[] the precise point positioning (PPP) solution[] among others, and the contribution of other satellite navigation systems,[] resulting in the Global Navigation Satellite System (GNSS), have lead to further enhancement of the GPS/GNSS solution and increased reliability of the displacement time series. Thus, the potential of real‐time GPS/GNSS monitoring with even a few millimeter accuracy, in an independent coordinate system for short‐ or long‐period monitoring, makes GPS a useful tool for SHM.…”

Integration of Single-Frequency GNSS and Strong-Motion Observations for Real-Time Earthquake Monitoring

“…The PSD results reflect that BDS has much larger noise than GPS, and that the GLONASS has a small offset; the combination of multi-GNSS systems represents the average of each single system. As shown in previous studies, the performance of multi-GNSS systems is better than that of the single GNSS system [28][29][30][31][32]. Figure 12 shows a comparison of displacements and PSD for different GNSS systems for the first experiment.…”