Research team monitors critical infrastructure using navigation satellites

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Researchers at Graz University of Technology have developed a new measuring system that can monitor the static and dynamic condition of buildings using just a few antennas.

Measurements for the InfraHealth project took place at the DC Tower in Vienna, a
Measurements for the InfraHealth project took place at the DC Tower in Vienna, among other locations. Image source: IGMS - TU Graz

From the outside, the Kölnbrein Dam in Carinthia, which is operated by Verbund and is Austria’s highest dam, and the DC Tower in Vienna, Austria’s highest building, do not have much in common, but for a research group led by Caroline Schönberger and Werner Lienhart from the Institute of Engineering Geodesy and Measurement Systems at TU Graz, they are of equal scientific interest. By taking measurements on these two buildings, the team was able to develop a satellite-based method for the static and dynamic monitoring of critical infrastructure as part of the InfraHealth project.

This makes it possible not only to track slow deformations that occur due to changes in the reservoir level of a dam wall, for example, using static measurements. Dynamic measurements can also be used to record building vibrations and detect damage or other critical changes based on deviations. Previously, different methods had to be used for static and dynamic measurements. The new method also enables continuous monitoring even during rain, snowfall, fog or storms.

Unique accuracy

"The high level of accuracy that we were able to achieve with the measurements in the InfraHealth project funded by the Austrian government is almost unique," says project manager Caroline Schönberger from the Institute of Engineering Geodesy and Measurement Systems at TU Graz. "We can record vibrations in the millimeter range or even below with satellites that are around 20,000 kilometers away from us. This project paves the way for the large-scale use of global navigation satellite systems (GNSS) for static and dynamic monitoring of critical infrastructure and thus for continuous monitoring of its safety, independent of environmental influences. This benefits not only building operators, but also their users."

This new measuring method uses local antennas and the publicly accessible GNSS signals from Galileo and GLONASS satellites. The antennas are attached to relevant measuring points on the structure, while another, so-called reference antenna is located relatively close by on stable ground. The antennas use the satellites to determine their position, for dynamic measurement every 0.05 seconds, i.e. at a frequency of 20 Hertz. Satellite and Galileo signals have proven their worth here, as the antennas can record their position more reliably. The researchers use this recorded raw data to calculate the frequency response of the structure.

Planning with virtual reality

Static measurement is more relaxed, as the measurement evaluation has a fixed interval that is always longer than one second - it can also be one hour or one day. Here, the combination of all three GNSS systems produced the best results, with GLONASS being added to Galileo.

To ensure in advance that the antennas would have contact with the satellites at the measuring points intended for them, the research team developed a tool that allowed them to carry out the entire planning in virtual reality. At the Kölnbreinsperre, the team determined in advance that not only the two antennas in the middle and halfway to the edge of the wall would be able to receive sufficient satellite signals, but also at the very edge. The transition to solid terrain is particularly important when monitoring dams.

Earthquake measured 550 kilometers away

Instead of six antennas, the team only needed two at the DC Tower: one to measure the building frequency and one to check whether the building also twists due to external influences such as wind. During the tests there, it became clear how accurately the new method can detect changes. During the series of measurements, the researchers were able to record the foothills of an earthquake around 550 kilometers away in northern Italy based on the movements of the tower. The quake with a magnitude of 5.7 on the Richter scale occurred on November 9, 2022 at 7:07 a.m. Central European Time near the Adriatic coast northwest of Ancona. Earthquake waves propagate at around 3 kilometers per second, so they travel around 540 kilometers in three minutes and at 7:10 a.m. there was a corresponding deflection at the DC Tower.

Werner Lienhart, Head of the Institute of Engineering Geodesy and Measurement Systems at Graz University of Technology, adds: "The combination of static and dynamic monitoring of infrastructure in one measuring system makes it possible to gain an in-depth understanding of the current state of health of a structure. This is particularly important for large engineering structures such as bridges or dams that are approaching the end of their planned service life."

Partners of TU Graz in the InfraHealth project were: Verbund Hydro Power GmbH, Leica Geosystems Austria GmbH, Disaster Competence Network Austria , pentamap GmbH

This research project is anchored in the Field of Expertise "Information, Communication & Computing", one of five strategic focus areas at TU Graz.