Evaluation of High-Rate GNSS-PPP for Monitoring Structural Health and Seismogeodesy Applications

This study evaluates the usability of the GNSS-PPP method for structural health monitoring and seismogeodesy applications. Two test scenarios were considered. The first test scenario included monitoring hormonic oscillations in amplitude of 5 mm to 20 mm with the frequency range of 0.2 Hz to 2.5 Hz that were generated using a shaking table, which has the ability to move in one direction in a horizontal plane. The second test scenario was carried out by simulating the El-Centro Earthquake as a seismogeodesy application. The used GNSS data comprised dual-frequency observations with a 10 Hz sampling rate. GNSS-derived positioning time series were obtained by processing the data using a post-mission kinematic PPP method and results were compared, in both the frequency domain and time domain, with LVDT (Linear Variable Differential Transformer) data, taking as a reference. Results show that the high-rate GNSS PPP method can capture the frequencies of harmonic movements comparable to the LVDT. The observed amplitudes of the harmonic oscillations are slightly different from the LVDT data at the order of mm level. These results demonstrate the ability of the high-rate GNSS PPP method to reliably monitor structural and earthquake-induced vibration frequencies and amplitudes for both the structural health and seismogeodesy applications

Hybrid Wavelet and Principal Component Analyses Approach for Extracting Dynamic Motion Characteristics from Displacement Series Derived from Multipath-Affected High-Rate GNSS Observations

Nowadays, the high rate GNSS (Global Navigation Satellite Systems) positioning methods are widely used as a complementary tool to other geotechnical sensors, such as accelerometers, seismometers, and inertial measurement units (IMU), to evaluate dynamic displacement responses of engineering structures. However, the most common problem in structural health monitoring (SHM) using GNSS is the presence of surrounding structures that cause multipath errors in GNSS observations. Skyscrapers and high-rise buildings in metropolitan cities are generally close to each other, and long-span bridges have towers, main cable, and suspender cables. Therefore, multipath error in GNSS observations, which is typically added to the measurement noise, is inevitable while monitoring such flexible engineering structures. Unlike other errors like atmospheric errors, which are mostly reduced or modeled out, multipath errors are the largest remaining unmanaged error sources. The high noise levels of high-rate GNSS solutions limit their structural monitoring application for detecting load-induced semi-static and dynamic displacements. This study investigates the estimation of accurate dynamic characteristics (frequency and amplitude) of structural or seismic motions derived from multipath-affected high-rate GNSS observations. To this end, a novel hybrid model using both wavelet-based multiscale principal component analysis (MSPCA) and wavelet transform (MSPCAW) is designed to extract the amplitude and frequency of both GNSS relative- and PPP- (Precise Point Positioning) derived displacement motions. To evaluate the method, a shaking table with a GNSS receiver attached to it, collecting 10 Hz data, was set up close to a building. The table was used to generate various amplitudes and frequencies of harmonic motions. In addition, 50-Hz linear variable differential transformer (LVDT) observations were collected to verify the MSMPCAW model by comparing their results. The results showed that the MSPCAW could be efficiently used to extract the dynamic characteristics of noisy dynamic movements under seismic loads. Furthermore, the dynamic behavior of seismic motions can be extracted accurately using GNSS-PPP, and its dominant frequency equals that extracted by LVDT and relative GNSS positioning method. Its accuracy in determining the amplitude approaches 91.5% relative to the LVDT observations

High-rate real-time PPP for dynamic motion detection in vertical direction

[EN] Nowadays, with the developments in GNSS (Global Navigation Satellite System) technology, the data storage and data processing capacity of GPS (Global Positioning System) receivers has been gradually increased. This situation is widely used in the detection and monitoring of horizontal and vertical vibrations that occur in the structure when high temporal resolution geodetic GPS receivers are under the influence of dynamic loads such as earth crust motions, wind load, traffic load, which affect man-made engineering structures. In the study, RT DF-PPP (Real Time Dual Frequency-Precise Point Positioning) method was applied together with a GPS sensor with a sampling interval of 20 Hz, using a steel bar mounted on a steel tree model designed as a structure model, and a steel bar on which different sensors can be integrated and can provide simulation of vertical motions in detecting vertical motions occurring in structures. To evaluate the performance of the method used and to test the performance of capturing vertical displacements, the DF-RP (Dual Frequency-Relative Positioning) method was taken as reference and the results were compared with the PP-PPP (Post Process-PPP) method using the IGS-Final (International GNSS Service-Final) product. When the results are compared with the RP and PP-PPP solutions in the frequency domain of vertical motions as a result of harmonic oscillations of the high-rate RT-PPP method, it has been seen that the amplitudes and frequencies are compatible with each other. Therefore, dynamic motions that occur as a result of natural events such as earthquakes, tsunamis, landslides and volcanic eruptions can be instantly and reliably monitored and detected by the high-rate RT-PPP method. When the results were evaluated in the time domain, an improvement was observed in the RMSE (Root Mean Square Error) and maximum values of RT-PPP and PP-PPP methods according to RP after filtering. When the statistical results are examined, vertical harmonic motions of the solutions made by using both RT-PPP and PP-PPP methods can be detected with accuracy below centimeters. These results clearly show that it can detect vertical dynamic motions in engineering structures such as bridges, skyscrapers and viaducts with RT-PPP method to evaluate. Thus, by detecting the effects of dynamic motions occurring in the structure on the health of the structure, a safe environment will be provided by making a rapid hazard assessment for life safety.Karadeniz, B.; Bezcioglu, M.; Yigit, CO.; Dindar, AA.; Akpinar, B. (2023). High-rate real-time PPP for dynamic motion detection in vertical direction. Editorial Universitat Politècnica de València. 455-460. https://doi.org/10.4995/JISDM2022.2022.1390645546

High-Rate Real-Time Single-Frequency PPP for Structural Motion Detection in Horizontal Directions

[EN] Thanks to advances in receiver and software technology, the high-rate GPS (Global Positioning System) technique has become very important in monitoring the dynamic behavior of man-made structures in both real-time and post-missions. Real-time monitoring of the changes in the behavior of structures due to effects such as natural disasters, wind effect, traffic loading is critical in order to take precautions in time. In this study, the performance of the Real-Time Single Frequency Precision Point Positioning (RT SF-PPP) method based on IGS (International GNSS Service) RTS (real-time stream) products to capture the behavior of dynamic motions was evaluated. The performance of the SF RT-PPP method to detect dynamic behaviors was evaluated based on 20 Hz single frequency GPS observations obtained from shake table experiments, including 10 mm amplitude and different oscillation frequencies including 0.1, 0.6, 1.0, 2.0 and 3.0 Hz. RT SF-PPP results were compared with reference LVDT (Linear Variable Differential Transformer) and relative (or double difference) GPS positioning both frequency and time domain. Results show that the high-rate RT SF-PPP method can capture the frequencies and amplitudes of harmonic motions and it is comparable to LVDT and Relative GPS positioning solutions. These results show that the high-rate RT SF-PPP method can monitor earthquake-induced real-time vibration frequencies and amplitudes, which is especially important for early warning systems.Bezcioglu, M.; Karadeniz, B.; Yigit, CO.; Dindar, AA.; Akpinar, B. (2023). High-Rate Real-Time Single-Frequency PPP for Structural Motion Detection in Horizontal Directions. Editorial Universitat Politècnica de València. 461-465. https://doi.org/10.4995/JISDM2022.2022.1390746146

Hybrid Wavelet and Principal Component Analyses Approach for Extracting Dynamic Motion Characteristics from Displacement Series Derived from Multipath-Affected High-Rate GNSS Observations

Nowadays, the high rate GNSS (Global Navigation Satellite Systems) positioning methods are widely used as a complementary tool to other geotechnical sensors, such as accelerometers, seismometers, and inertial measurement units (IMU), to evaluate dynamic displacement responses of engineering structures. However, the most common problem in structural health monitoring (SHM) using GNSS is the presence of surrounding structures that cause multipath errors in GNSS observations. Skyscrapers and high-rise buildings in metropolitan cities are generally close to each other, and long-span bridges have towers, main cable, and suspender cables. Therefore, multipath error in GNSS observations, which is typically added to the measurement noise, is inevitable while monitoring such flexible engineering structures. Unlike other errors like atmospheric errors, which are mostly reduced or modeled out, multipath errors are the largest remaining unmanaged error sources. The high noise levels of high-rate GNSS solutions limit their structural monitoring application for detecting load-induced semi-static and dynamic displacements. This study investigates the estimation of accurate dynamic characteristics (frequency and amplitude) of structural or seismic motions derived from multipath-affected high-rate GNSS observations. To this end, a novel hybrid model using both wavelet-based multiscale principal component analysis (MSPCA) and wavelet transform (MSPCAW) is designed to extract the amplitude and frequency of both GNSS relative- and PPP- (Precise Point Positioning) derived displacement motions. To evaluate the method, a shaking table with a GNSS receiver attached to it, collecting 10 Hz data, was set up close to a building. The table was used to generate various amplitudes and frequencies of harmonic motions. In addition, 50-Hz linear variable differential transformer (LVDT) observations were collected to verify the MSMPCAW model by comparing their results. The results showed that the MSPCAW could be efficiently used to extract the dynamic characteristics of noisy dynamic movements under seismic loads. Furthermore, the dynamic behavior of seismic motions can be extracted accurately using GNSS-PPP, and its dominant frequency equals that extracted by LVDT and relative GNSS positioning method. Its accuracy in determining the amplitude approaches 91.5% relative to the LVDT observations