ABSTRACT: GNSS has become one of the most widespread measurement technologies, widely used in GIS, mobile mapping applications and civil engineering. Utilisation of differential techniques offers cm-level positioning accuracy. Identified drawbacks are the requirement for line of sight to the satellites and accuracy dependent on the geometric distribution of the satellites. Especially the latter is paramount for any surveying or mobile mapping application in the urban environment. The utilisation of additional constellations (GLONASS, GALILEO or COMPASS) only partly mitigates the problem. Locata is an Australian terrestrial positioning technology, based on the pseudolite concept. It’s unique in its utilisation of the 2.4GHz ISM band and proprietary TimeLoc procedure, allowing for network synchronisation at the nanosecond level. This paper focuses on the tight integration of GNSS with Locata, in order to address the described drawbacks and to provide cm level positioning in areas currently “difficult ” for GNSS – such as urban canyons. This paper describes the intended deployment and utilisation of the integrated system in the typical urban environment where availability of GPS can be limited or even non-existent, depending on the time and location. The verification of the integration methods has been carried out using simulated GPS and Locata data. Also presented is an application simulation in a typical urban canyon environment (Canary Wharf, London, UK) using proprietary software developed at the University of Nottingham. Simulation of the proposed integration algorithms, using a real life scenario, has shown promising results with centimetre-level positioning accuracy on the moving platform. The algorithm provides code ambiguity estimation for both Locata and GPS on-the-fly, without prior knowledge of the position, providing predominantly 3D position on the cm level. 1
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