AbstractThe Hong Kong–Zhuhai–Macao Bridge (HZMB) is the longest sea-crossing bridge in the world. The primary Global Navigation Satellite System (GNSS) control network of the HZMB has the outstanding characteristics and difficulties of long distance across the sea (nearly 32 km) in an approximate east–west direction, poor satellite positioning environment, high precision requirement of construction positioning, long construction period, and complicated transformations of the coordinate systems of China, Hong Kong, Zhuhai, Macao, and the HZMB project. Taking the primary GNSS control network of the HZMB as an example, this paper studied the key technical issues in establishment and repetition survey of the primary GNSS control network of a large-scale and high-precision sea-crossing bridge. Firstly, the three-dimensional engineering coordinate system based on International Terrestrial Reference Frame (ITRF) and the two-dimensional plane coordinate system with projection length deformation less than 5  mm/km were designed and established according to the engineering characteristics and requirements. Secondly, the control point selection, networking, and observation schemes were designed. Thirdly, the data processing technologies of high-precision GNSS control network of sea-crossing bridge and tunnel engineering project, including International GNSS Service (IGS) reference station technology, satellite orbit fixing technology, various error correction techniques, and engineering datum network technology, were studied and put forward. Fourthly, the accuracy analysis of baseline solution and network adjustment was carried out by using the fifth repetition survey data of the primary GNSS control network of the HZMB. Finally, the repetition survey results of the network were compared and analyzed.

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