The Aurach Bridge is located in Upper Austria on the A1 West Motorway, the main connection between Salzburg and Vienna. The bridge is approximately 500 m long, built as a composite steel–concrete slab structure, and divided into six spans. Construction began in 1939, but works had to be stopped in 1941 due to the war. They resumed only in 1958, and the bridge was completed in 1961. The maximum span between two supports is 72 m, and the bridge reaches a maximum height of 48 m above the terrain. Between 1989 and 1991, the composite reinforced-concrete deck slabs were replaced and the roadway was slightly widened.

The bridge is scheduled to be replaced by a new structure. As it is one of the busiest motorway sections in Austria, it cannot simply be demolished and rebuilt; construction must proceed while maintaining ongoing traffic. Ensuring that the roadway geometry remains within defined tolerances is a critical safety factor.

For this reason, we began measurements one year before construction started. This allowed us to collect data on the current condition of the existing bridge across all four seasons and under varying weather conditions.

Our task was to continuously monitor the bridge abutments and piers, before and during heavy earthworks, for settlements and deformations using 14 GNSS sensors.

The reference station was installed approximately 300 m away on a known stable foundation.