Performance of precise marine positioning using futureudmodernised global satellite positioning systems and audnovel partial ambiguity resolution technique

摘要

The International Maritime Organisation (IMO) established a set of positioning requirements forudfuture Global Navigation Satellite System (GNSS) constellations in IMO resolution A.915. It isudimportant to be able to determine if these requirements can be met, and what shore infrastructureudwould be required. This thesis describes the collection of data in a marine environment and theudanalysis of these data with regards to the requirements.udThe data collection exercise was held at the beginning of May 2008 and saw THV Alertudnavigate into Harwich Harbour whilst Global Positioning System (GPS) observation data wereudrecorded from onboard the vessel and from shore-based reference stations. Additional data wereudobtained from nearby Ordnance Survey reference stations, and two total stations were used toudtrack the vessel’s passage to provide a truth model. Several modernised GPS satellites wereudtracked. The data were processed under different scenarios, using software developed at UCL,udand the positioning performance was analysed in the context of the IMO requirements. Potentialudperformance improvements from modernised GPS and Galileo were then discussed.udProviding integrity through single-epoch real-time kinematic positioning, required to meetudthe strictest IMO requirements, is particularly difficult. The identification of phase observationudoutliers is not possible before the integer ambiguities are resolved, but an undetected outlierudcould prevent successful ambiguity resolution. It will not always be necessary to fix all theudambiguities to achieve the required positioning precision, particularly with a multi-GNSS constellation.udThis thesis introduces a new algorithm for partial ambiguity resolution in the presenceudof measurement bias. Although computationally intensive, this algorithm significantly improvesudthe ambiguity resolution success rate, increasing the maximum baseline length over which theudhighest requirements are met with dual-frequency GPS from 1 km to 66 km.