1. Introduction

The commissioning of a new (renewed) railway line requires strict observance of the notified national safety rules, rules and instructions for the construction and maintenance of the upper structure of the railway.
The estimation of the design parameters achieved for the elements of the upper structure of the railway line at this stage is achieved by reading graphical results from a track wagon.

Vector-Bul Ltd. developed and experimentally applied a new approach in the survey of parameters of the upper structure of the railway track of renewed sections of the railway network in Bulgaria. For this purpose, a railway carriage structure has been developed in which high precision measuring instruments are installed.

2. Main parts of the railway trolley and its measuring equipment:

  • Construction – the rail trolley is made of aluminum profiles. The wheels are made of technical plastic with high impact resistance and wear resistance. They have good electrical insulation properties. The design of the trolley provides stability and non-deformability.
  • GNSS receiver for location measurement – a GNSS receiver is used by a company offering a licensed GNSS network solution with real-time corrections received online. The antenna of the receiver is located on a specially designed stand. It provides alignment of the receiving antenna and the rail at a certain fixed height. After moving the trolley to a point for complex recording, geographic coordinates are recorded. The accuracy of the plan is in the range 0.7-1.5 cm, and in height 1.5-3 cm.
  • Slope to determine the cant – the height between the two track threads is measured with an inclinometer. The tool provides high precision of the inclination angle with respect to the horizontal plane. The accuracy of determination of the overhang is less than 1 mm based on a track gauge of 1.5 m. The transverse slope data is entered into the mini computer with records at a predefined time interval in milliseconds.
  • Electronic distance gauge for axis distance measurement (railway) – the device is mounted on the body of the measuring trolley. The 1435mm track gauge accuracy is 0.01mm.
  • Laser Flash Measurement System (Railway Smoothness Criterion) – the laser system is composed of laser and radiation trays. The devices are placed at three consecutive points every 10m. The report is made at the midpoint. The geometric measurement is performed using the chord method. The transverse distance from the track axis to the laser chord constructed between the first and third points is recorded.
  • Mini PC for device management – using the railway carriage and the built-in tools in the mini computer to collect data on:
    – The position of the railway in plan to the nearest 1.5 cm.
    – Railway mileage.
    – Rail elevation.
    – Super elevation of the two track threads relative to each other to within 1mm.
    – The distance between the two track threads to the nearest 0.01 mm with a standard track gauge of 1435 mm.
    – Overall distance of the facilities near the railway – front of a pole of a contact network (catenary), retaining walls, stands, supports of overpasses, platforms, height to a contact rope.
    – Longitudinal slope of the track.
  • Measurement of the distance from the rail head to the contact wire – the instrument used to measure the distance from the rail head to the contact wire has the ability to electronically record information by recording the date and time of measurement. Runs in parallel with other measurements.
  • Software for the collection of primary data – all received measurement data is stored in a file that stores date information, measurement time, distance meter, inclinometer, horizontal distances, X, Y, Z coordinates, point number. The graphical presentation of the results is performed in the drawing for a longitudinal profile of the measured path, with a longitudinal profile for the measured track gauge, measured elevation and distance to the design position of the centerline. The regulatory tolerance in mm is also displayed giving information about the points where we have exceeded the regulatory values.
  • Authorial software for processing and analysis of the obtained measurement results – the final data are processed with the specialized software of Vector-Bul Ltd. for processing of data from measurements with a railway carriage.
  •  Estimation of the studied parameters according to the six-point system – after processing the input data from the tools on the computer using specialized software of Vector-Bul, the parameters of the railway track and the contact network are evaluated. An appraisal table is attached:

3. Conclusion

The proposed railway survey approach can fulfill the following tasks:

  • Inspection of parameters of newly constructed railway line for commissioning.
  • Rehabilitation projects.
  • Track smoothness studies.
  • Executive documentation.
  • Technical support during railway repair or renewal.
  • Inspection of the current state of the railway.