Radar Satellite Observations of Bridge Deformations- A new Method for Monitoring without applied Sensors.

The evaluation of structures with the help of remote sensing radar satel-lites offers new possibilities for the permanent monitoring of deformations of entire structures and their surroundings. Instead of equipping structures in-dividually with expensive discrete sensors or surveying them terrestrially with expensive instruments such as laser scans or drones in a labor-intensive manner, deformations can be continuously recorded with the use of radar satellite data. In the future it might be possible to centrally monitor, evalu-ate and assess various bridge deformations network-wide.
A recently completed research project on Semmering-Autobahn S6 in Austria investigated new approaches to improve deformation detection based on radar-satellite measurements using open data form ESA’s Sentinel 1 Mis-sion. The aim was to evaluate how satellite data can best contribute to de-formation monitoring of engineering structures and how structural thermal deformation can be compensated. On the S6 Schottwien bridge (main span 250 m) corner reflectors (artificial back scatterer with known coordinates), temperature sensors and inclination sensors with low energy consumption were installed. A new proposed temperature compensation model, which is based on thermodynamic parameter studies, can predict the structure tem-perature of the bridge only with using central network weather data. The ac-curacy of radar satellite measurements can be dramatically improved without any sensors applied at all.
An annual cycle shows that the satellite measurement has an accuracy of 2- 3 mm related to an installed long-term levelling reference sensor system and are well suited for monitoring long span bridges