Innovative mobile method to determine railway track axis position in global coordinate system using position measurements performed with GNSS and fixed base of the measuring vehicle

Abstract The shape of the railway track axis and its position in the global coordinate system are essential when defining design parameters of the railway. Correct reconstruction of these quantities is vital for both verifying the compliance of real track parameters with the design and for diagnosing, as all track deformations can also be defined as deviations of real parameters from their design values. The measurements of quantities related to the railway track geometry can be divided into global and local ones. Global measurements determine the position of elements in the global system of geographic coordinates, while local measurements give relative positions of elements with respect to other elements (e.g. lateral inclination at a given kilometre of the railway track) or temporary deviation of parameters from their assumed value (e.g. various track deformations). Depending on the applied measuring method, either global or local parameters are determined, or both of them simultaneously. The article proposes an innovative method to determine the railway track axis position, which makes use of Global Navigation Satellite Systems (GNSS) receivers distributed in such a way as to form a geometric constraint called the fixed base. The analysis of theoretical properties and metrological attributes of the fixed base is presented. All theoretical analyses have been verified experimentally.