Determining Rail Track Axis Geometry Using Satellite and Terrestrial Geodetic Data

In this paper, a multi-sensor data acquisition system and a method for extracting the track axis geometry of railways are introduced. The rail track surveying system employs GPS and a tracking total station for absolute referencing, aided by a biaxial inclinometer for reducing the data into a common datum in canted sections and a digital odometer for linear referencing. Track axis extraction depends on rail track positional data, whereas its geometric modelling is performed on the basis of design elements using the bearing diagram and the Generalised Least Squares (GLS) method on the horizontal and vertical track layout. In addition, a supplementary algorithm for computing the rail curvature is presented. Extended test runs were conducted to validate the feasibility of the system and the method. The test results show that a directional uncertainty of better than 0.01° in tangent sections and deviations between the actual and computed track radii of better than 1% in curved sections are achievable.