The measuring sensor is mounted on top of the roof of the track recording car, the measured data are transmitted to the processing unit inside the track recording car. Via an oscillating mirror, a high frequency modulated, temperature-stabilized laser beam scans a range of ±35° above the track recording car lateral to the travelling direction 100 times per second. When the laser beam hits a wire, the light is reflected and the receiving unit assesses the reflection. Analyzing the phase shift between outgoing and reflected light determines the distance from the mirror to the catenary wire. The measured polar coordinates are converted into x-y coordinates by taking the angle of the mirror into account.

The measured stagger and height values are referenced to the track plane (a plane through the top of both rails) by compensating for car body movements and bogie rotation. Utilizing optical gauge measurement data, the stagger values can also be referenced to the track center line.

The conditioned measured data are transmitted via Ethernet to the main server of the recording car and stored together with the other measured data. During the measuring run, the catenary parameters can be shown together with other parameters such as superelevation or curvature.

To keep the system’s transmitting and receiving components clean, the measuring sensor is equipped with a sophisticated hot steam/vacuum cleaning system. This is operated from the cabin and allows effective cleaning of the optical components even while measuring.

The laser beam is eye safe for distances greater than 2.5 m. As an additional laser safety measure, the scanner cover is closed automatically at speeds below 3 km/h. The laser scanner is fitted with continuous, automatic calibration at intervals of 20 milliseconds. The system is not influenced by ambient light.

In combination with the automatic pole detection system, the system allows the analysis of the catenary wire position and pole-triggered track location synchronization.