GPS-Synchronization of a Seismic Accelerometer and a Ground-Based Interferometric Radar for Structural Health Monitoring

Abstract

This paper presents a seismic accelerometer with GPS-synchronization based on the pulse per second (PPS) signal provided by the GNSS satellite network. This feature is essential for a Structural Health Monitoring (SHM) network that includes different sensors as for example accelerometers, cameras and a ground-based radar. The PPS signal is widely used in applications of timing synchronization because of its high accuracy and long-term stability. The common time-base between devices allows the internal time of the devices to be resynchronized every second, avoiding drift. In this work, we developed and tested acquisition board for seismic accelerometer with custom firmware designed to provide synchronized data recorded by different acquisition systems. The universal time (UTC) synchronized with PPS has been assigned to the data of each devices. The developed board has been tested with simultaneous acquisition a seismic accelerometer in MEMS (Micro Electro-Mechanical System) technology and a ground-based interferometric radar,both GPS synchronized. The two sensors are equipped with high precision GNSS receiver u-blox F9, that provide the UTC data and the PPS signal. To validate the synchronization system, the accelerometer and the ground-based radar were operated simultaneously to detect the oscillations of a moving target (a metallic swinging rod). The results of the experiment demonstrate that the sensors are well synchronized and the evaluations of the displacement are very similar, with good accuracy for performing dynamic structure monitoring. It is worth noting that this comparative analysis has highlighted the role of the automatic synchronization.