Objective With the autonomous and intelligent development of urban rail transit, high-precision positioning information has become a prerequisite for train autonomous driving. Therefore, it is particularly important for urban rail transit trains to obtain high-precision positioning information and eliminate interference factors in the ranging process.

Method The UWB（Ultra-Wideband）ranging principle and clock error analysis method is expounded. Focusing on urban rail transit transportation scenarios, and based on UWB positioning technology for urban rail transit trains, two major factors affecting UWB signals are selected (directional antenna layout asymmetry and metal obstacle occlusion). A theoretical analysis of the ranging errors caused by these two interference factors is conducted, and field tests are carried out on Zhangjiang Urban Rail Transit Comprehensive Test Line in Shanghai. By collecting the UWB module ranging information output, changes in ranging information and train positioning performance under the influence of these two interference factors are analyzed, and the impact of these two interference factors on train positioning error is compared.

Result & Conclusion The directional antenna layout asymmetry leads to inconsistent ranging performance between base stations on both sides of the track, which is primarily observed in short-distance ranging scenarios, while in long-distance ranging, the train positioning performance remains relatively stable. On the other hand, metal obstruction can cause a ranging error with a mean value of +0.36 m.