1. Measuring frame with fixed vertical distance to the rail surfaces
2. Inertial measuring unit (IMU)
3. Sensors of the track gauge measurement
4. Laser beams to scan the track gauge
5. GPS antenna
6. Navigation computer
7. Blue curves: space curves of both rails derived from the measurements along the track, synchronised with GPS data
8. Green line: track design line
9. Red arrows (horizontal): alignment defects, calculated from the space curve
10. Orange arrows (vertical): longitudinal level defects, calculated from the space curve
from Plasser & Theurer