J. Geng

Performance of Precise Point Positioning with Ambiguity Resolution for 1- to 4-Hour Observation Periods

Abstract Recent progress in integer ambiguity resolution at a single station has made it possible to achieve high positioning accuracy in static precise point positioning (PPP) using a short period of observations. In this paper, 12 stations across Europe are used to conduct short-period (i.e. one, two, three and four hours) static PPP with ambiguity resolution from Day 245 to 251 in 2007. It is demonstrated that, when over three hours of observations are used, PPP can achieve a success rate of 100% for ambiguity resolution, a 3D positioning accuracy of about 1.0 cm and an occurrence of less than 1.0% for degraded solutions. Moreover, for the fixed solutions, increasing the observation period hardly improves the horizontal positioning accuracy while still improving the vertical one. Therefore, it is proposed that at least three hours of observations should be used in the ambiguity-fixed static PPP if a reliable millimetre positioning accuracy is required in the engineering applications.

Application of Real-Time Precise Point Positioning and GIS for Rail Track Deformation Monitoring of the Qinghai-Tibet Railway

The Qinghai-Tibet railway is the highest railway in the world. The operational conditions of this railway are very harsh, such as occurrence of earthquake, potential melting of frozen soil, and severely cold and thin air. Real time monitoring the deformation of the railway system for maintaining safe operation has posed a big challenge. Extensive document review conducted by the authors reveals that the current monitoring systems do not include monitoring of the deformation of critical railway element - rail track. The authors propose in the paper a novel approach which could be implemented to conduct an automated, real time and cost-effective monitoring of whole rail track system. This new monitoring system consists of two sub-systems: a real-time rail track monitoring system with precise point positioning (PPP), and the geographical information system (GIS) to support the development, analysis and visualization of real-time spatial and attribute data sets. Details about the system integration are also presented in the paper. The approach will have general significance to the monitoring of any large civil engineering infrastructures.