Multi-antenna GPS Monitoring System Enhances Building Health

Multi-antenna GPS Monitoring System Enhances Building Health

Large buildings undergo deformation and vibration under internal and external forces. For monitoring building structural health, the ability to measure subtle positional changes and vibration patterns is crucial.

In the measurement process, the optimal use of Global Navigation Satellite Systems (GNSS) with Inertial Measurement Units (IMU) to accurately measure slight changes in shape, angular velocity and acceleration in three-dimensional space is important for determining building safety.

To address this, Professor Ding Xiaoli, Director of Research Institute for Land and Space at The Hong Kong Polytechnic University (PolyU) and Chair Professor of Geomatics in the Department of Land Surveying and Geo-Informatics, developed an innovative measurement system. By receiving signals from GNSS and developing new computation models, the system significantly enhances the measurement accuracy while reducing the cost of monitoring building safety.

Multi-antenna GPS Structure Monitoring System - Integration of Improved Hardware and Software

"The Global Navigation Satellite Systems are not a new technology. In fact, modern smartphones can perform basic positioning based on GNSS," noted Professor Ding. He observed that in general newer smartphone models and software versions achieve higher accuracy in positioning due to their ability to receive signals from more satellites.

Historically, GNSS operated with just over 20 satellites, but recent advancements have significantly increased the number of operating satellites, as a result of increased satellite systems, especially in densely populated urban areas where satellite signal blockage is common.

However, a measurement system for precise surveying typically requires an accuracy as high as millimeters. Therefore, accurate reception and interpretation of data from satellites to achieve high measurement accuracy are the key challenges.

In response, Professor Ding developed a series of GNSS signal processing models and algorithms, alongside a Multi-antenna GPS measurement device. Data from multiple GNSS and IMU are integrated, significantly improving the stability and accuracy of the measurements.

Results have demonstrated that the technology could achieve an accuracy level of close to 1.0 millimeter, far surpassing ordinary GNSS devices. Additionally, Professor Ding's team invented a multi-antenna GNSS technology, allowing a single GNSS device to sequentially receive satellite signals from multiple antennas, lowering the measurement cost.

In addition to hardware, software is also critically important to the measurement quality. Software includes algorithms and data processing systems.

"Satellite signals may be affected by atmospheric and other observational conditions, causing many errors. Our algorithms and software aim to process and analyze the collected data in real-time to predict more accurately change in the position and shape of a building. While both utilize GNSS, the complexities differ significantly, beyond the capability of a typical smartphone."

Ensuring Safety of PolyU Footbridge

This system has been installed on various large-scale structures, including the pedestrian Footbridge connecting PolyU's new and old campuses.

"As part of the pedestrian bridge structural health monitoring system, we have installed GNSS measurement devices at the upper and lower parts of the bridge to monitor its structural safety especially during extreme weather or situations," explained Professor Ding, as the system collects and analyzes satellite data in real-time to monitor the bridge displacement and issue timely warnings. This surveillance system operates without the need of manual supervision, reducing the overall cost of the system effectively. "The system can also be installed on slopes to predict potential risks of slope failures."

The system has been awarded the "President's Awards for Outstanding Achievement in Knowledge Transfer (KT)" by PolyU and has been applied in multiple large-scale building projects.