Accuracy of kinematic track measurement

The use of a total station, inertial measurement unit, and laser tracker on a track measurement trolley is comprehensively examined regarding achievable accuracy and fully meets high expectations.

The geometry of the tracks on a slab track must be checked for compliance with tolerances before handover, according to the guidelines of Deutsche Bahn, through a so-called final documentation. This documentation requires measurement results – horizontal and vertical deviation from the plan data, super elevation, track gauge, short- and long-wave relative geometry – at each rail fastening. With a kinematic measurement using a total station, inertial measurement unit, and laser detector mounted on a track measurement trolley, this measurement process can be carried out significantly more effectively than with the previous conventional method, which requires stops at each sleeper. The accuracies with which the results of the new method can be obtained were determined by experienced RSRG staff through an extensive measurement program consisting of multiple reference and test measurements. 
 

A dual conventional measurement, whose accuracy has been confirmed over many years, was used as a reference. The kinematic test measurements were carried out four times. The extensive analysis of the results confirmed compliance with high accuracy requirements. The accuracy of the horizontal and vertical track position determined by the study is within +/- 1 mm, and that of the super elevation and track gauge is within +/- 0.5 mm. The position of the rail fastenings, required for the output of the results, can be determined with an accuracy of +/- 3 cm. The measurement method achieves daily outputs that are six times higher compared to the conventional method. This allowed RSRG to demonstrate both increased efficiency and high precision.