Accurate absolute measurement of existing lines is a task of fundamental importance to provide scientific basis for reconstruction. Traditional railway track survey methods in combination with classical geodetic surveying apparatus such as total stations cannot meet the requirements of surveying efficiency. Accurate, reliable and fast existing railway surveying applications call for an innovative method that can obtain high-precision, continuous and uniform railway track axis position in short time without interrupting the railway traffic. This paper provides an innovative solution to track axis surveying based on the integrated technique of global navigation satellite system (GNSS), inertial navigation system (INS) and odometer. GNSS/INS/odometer system does not depend on a high-precision track control network, which can operate in mobile surveying mode and significantly improve the measuring speed from 0.15 km/h to 5 km/h compared to conventional methods. Compared with satellite surveying methods, this solution for the measurement of existing line axis can obtain continuous and high-precision results in the absence of satellite signals. The results of field tests on the Zhengzhou-Xuzhou high-speed railway track show that the measurement errors are less than 0.6 cm and 1.1 cm in horizontal and vertical directions, respectively, and this measuring system is able to maintain high precision of 5 cm with a GNSS outage of 700 s, which can meet the accuracy requirements of China Specifications for Survey Engineering of High-speed Railway and serve visualization, assessment and design process of existing railways.

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