Abstract
Immersed tunnel elements need to be exactly controlled during their immersion process. Position and attitude of the element should be determined quickly and accurately to navigate the element from the holding area to the final location in the tunnel trench. In this paper, a newly-developed positioning and attitude determination system, integrating a 3-antenna Global Navigation Satellite System (GNSS) system, an inclinometer and a range-measurement system, is presented. The system is designed to provide the absolute position of both ends of the element with sufficient accuracy in real time. Special attention in the accuracy analysis is paid to the influence of GNSS multipath error and sound speed profile. Simulations are conducted to illustrate the performance of the system in different scenarios. If both elements are very close, the accuracies of the system are higher than 0.02 m in the directions perpendicular to and along the tunnel axis.
Highlights
The Global Navigation Satellite System (GNSS) multipath errors cannot be removed by differential methods since multipath is a localized phenomenon, which strongly depends on the environment of the measurement site, the performance of the antenna, and of the receiver
The GNSS multipath errors cannot be removed since multipath is a localized phenomenon, which strongly depends on 10 ofthe environment of the measurement site, the performance of the antenna, and of the receiver
In order to further estimate the effect of multi-path errors on the resulting coordinates baselines, we analyze the measured data ofdata threeofGNSS
Summary
An immersed tunnel consists of one or more elements that are prefabricated, floated to the site, installed one by one, and connected to the previous one in the tunnel trench under water [1]. The traditional positioning method for immersed tunnels is the measurement tower system. The traditional traditionaltower positioning method forofimmersed immersed tunnels is the the measurement measurement tower system. Three total stations onshore are used to measure the positions of prisms fixed to the top element. RTK, short for real timeelement kinematic) in real time positions of prisms are measured using total stations In order to avoid the influence of deformation of the measurement currently the deepest immersed tunnel in the world. A taut-wire relative position of the elements be obtained the distance d and system angles, includes τ and ω, distance sensors, cable units and other accessories.
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