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Mathematical Models and A Case Study of The Locata Deformation Monitoring System (LDMS)

SUMMARY Locata Corporation’s positioning technology “Locata” is a terrestrial-based RF-ranging technology that provides high accuracy position solutions using a network (LocataNet) of time synchronised pseudolite-like transceivers (LocataLites). LocataLites can be installed in locations to ensure optimal network geometry for a certain coverage area. With batch least squares processing, millimetre precision is achievable and thus provides an opportunity to address shortcomings of current deformation monitoring systems. A prototype of a Locata Deformation Monitoring System (LDMS) has been developed, consisting of four fundamental parts, namely data acquisition, quality control and validation, coordinate solution, and deformation monitoring. This paper focuses on the mathematical models. To validate the feasibility of this system, simulation tests and a deformation monitoring field trial have been conducted. Dam simulation studies have been conducted at The University of New South Wales using four LocataLites and six monitoring points for deformation analysis with the LDMS. An artificial deformation of 10 millimetres has been injected into three components of a monitoring point’s coordinates, and the LDMS identified the deformed point successfully as well as the amount of deformation. A deformation monitoring trial has also been conducted at the Tumut Pond Dam in Cabramurra, NSW, Australia, where long term deformation history is available for comparison. After analysing the deformation network geometry suitable for millimetre-level precision of position components, and LocataLites’ line-of-sight visibility, four LocataLites, one receiver and a weather station have been installed. Measurement data, including pseudorange, carrier phase and atmospheric data, have been collected and post-processed for deformation analysis using the batch least squares method by the LDMS. After generating 3D coordinate solutions, statistically significant movement (deformation) was identified by standard deformation analysis. These results have been compared with previous total station based deformation surveys which show that Locata can continuously deliver high accuracy positioning.