Measuring Railway Track Irregularities at High Accuracy and Efficiency Based on GNSS/INS/TS Integration

Measuring the railway track irregularities (abbr. Irr) with sub-millimeter accuracy is vital for the travel safety of high-speed trains. In comparison to the traditional total station (TS)-based track inspection trolley (TIT) for track irregularity examination, the integration of global navigation satellite system (GNSS) and inertial navigation system (INS) is more time-efficient but less accurate in longwave irregularity detection. To achieve high accuracy and high survey efficiency, a GNSS/INS/TS integrated irregularity measuring (GIT-Irr) system is proposed based on the attitude-inferred irregularity measuring method utilizing TS constraint. In addition, to reduce the conversion error of TS coordinates from local engineering frame to local geo-frame, TS-aided calibration in the deviation domain is recommended in the GIT-Irr system. A field test was carried out near the Baotou East railway station in China in order to validate the performance of the proposed system. Four sets of independent measurements are collected together with an external reference from a TS-based TIT. The results demonstrate that the proposed system increases the surveying ability of shortwave and longwave alignment irregularities by about 5% and 75%, respectively. Under a 3-sigma confidence level, shortwave alignment irregularities are 0.50 mm and 0.57 mm in horizontal and vertical directions, respectively, while those of the longwaves are 1.78 mm and 2.06 mm. Therefore, the proposed GIT-Irr system provides great potential for highly efficient sub-millimeter track irregularity measurement.