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Determination of Moving Chord Length for Determining the Curvature of In-Service Railway Track

Koc Władysław

Problemy Kolejnictwa

2022

Z. 197

147--160

The paper deals with the still unexplained issue of the choice of chord length, which will be the most benefi cial when determining the horizontal curvature of railway track with the use of the moving chord method. In the railway track – with an incorrect choice of the chord length – the horizontal track deformations and coordinate measurement error may cause irregular curvature diagrams, which will be difficult to interpret. The study analysed three test geometric layouts adapted to the speeds of 80 km/h, 120 km/h and 160 km/h (the radii of circular curves determined as a result of the curvature estimation performed were approximately 410 m, 880 m and 1480 m, respectively). The lengths of the moving chord in the range of 10÷50 m were considered. On the basis of the conducted analysis, it was unequivocally demonstrated that the chord length used to determine the curvature in the railway track should depend on the value of the radius of the circular curve. Approximate lengths lc were proposed depending on the range of the RCA radius. The adaptation of the moving chord method to the adopted measurement procedure presented in this paper and the way of using the obtained curvature diagram, provide the appropriate application basics.

Determining horizontal curvature of railway track axis in mobile satellite measurements

Koc Władysław, Wilk Andrzej, Specht Cezary, Karwowski Krzysztof, Skibicki Jacek, Czaplewski Krzysztof, Judek Sławomir, Chrostowski Piotr, Szmagliński Jacek, Dąbrowski Paweł, Specht Mariusz, Grulkowski Sławomir, Licow Roksana

Bulletin of the Polish Academy of Sciences. Technical Sciences

2021

Vol. 69, nr 6

art. no. e139204

The article discusses the applicability of a novel method to determine horizontal curvature of the railway track axis based on results of mobile satellite measurements. The method is based on inclination angle changes of a moving chord in the Cartesian coordinate system. In the presented case, the variant referred to as the method of two virtual chords is applied. It consists in maneuvering with only one GNSS (Global Navigation Satellite System) receiver. The assumptions of the novel method are formulated, and an assessment of its application in the performed campaign of mobile satellite measurements is presented. The shape of the measured railway axis is shown in the national spatial reference system PL-2000, and the speed of the measuring trolley during measurement is calculated based on the recorded coordinates. It has been observed that over the test section, the curvature ordinates differ from the expected waveform, which can be caused by disturbances of the measuring trolley trajectory. However, this problem can easily be overcome by filtering the measured track axis ordinates to obtain the correct shape – this refers to all track segments: straight sections, circular arcs and transition curves. The virtual chord method can also constitute the basis for assessing the quality of the recorded satellite signal. The performed analysis has shown high accuracy of the measuring process.