Abstract
In recent years, a dynamic development of satellite positioning techniques using both static and mobile GNSS coordinates register mode can be observed. In addition, still developing Real-time GNSS Networks, post-processing algorithms and another measurement signal analysis algorithms, make the satellite measurements increasingly used in railway industry sector. In the article the possibilities which follows from the mobile satellite measurements in railway engineering are briefly presented. In the years 2009-2015, the authors conducted a series of field investigations on operated railway lines. The obtained results of these measurements led to the development of a number of algorithms that increase the range of applicability of GNSS measurements. The analysis of obtained results also showed how the accuracy of the measurements have increased since 2009. The achieved accuracy has been increased due to a development of GNSS positioning systems as well as improvement of the measurement methodology, i.e. configurations of satellite receivers and layouts of their placement on a mobile measuring platform. It was also found that the development of data analysis algorithms contributed to the increase in the obtained accuracy in assessment of a railway track axis shape. The authors indicate the possibilities of applying GNSS techniques at various stages of construction and operation of railways. According to the authors, the most important advantage of both the presented measurement technique and computational methodology is the ability to effectively and relatively low-cost data acquisition regarding the existing state of the railway line. These data can be successfully used to design changes to the geometry of railway lines, and therefore satellite positioning has enormous application potential in the process of modernization of operated railway lines.
Highlights
The railway tracks were subjected to the evaluation of their shape due to the direct relation between the quality of the geometric layout and the safe and comfortable exploitation of the track
There is an increasing need to be able to identify location of trains on the network in order to manage the capacity of the railway lines [7]
The comparative assessment concerned straight sections of railway and tram routes arranged on monotonous longitudinal inclinations. In such a geometric arrangement, the determination of the track axis basing on the measured coordinates is unambiguous mainly because there is no need to identify the distribution of curvature, and the measurement has no errors due to the existing of a cant in arcs
Summary
The railway tracks were subjected to the evaluation of their shape due to the direct relation between the quality of the geometric layout and the safe and comfortable exploitation of the track. The classical methods of geodesy are developed, especially the methods using tacheometry [12, 13] This measurement technique is accurate and precise, it requires a track-side geodetic reference network. Alternative techniques for determining the shape of the track are based on a laser scanning This measurement along with post-process algorithms allows to extract from the recorded cloud of points a virtual axis of the railway track with a high accuracy – few millimeters [14]. Another measurement technique that usually assists the major and prime technique for track axis measurement is the inertial technique INS [10] The advantages of this technique are mainly due to the fact that the measurement signal is not related to any external reference system as for example in tacheometric or satellite measurements. Using the possibilities which follow from the GNSS techniques, a series of algorithms for evaluation and design support were developed [5, 16, 17, 18]
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