Research On Fusion Methods Of The Signals Of Opportunity And GNSS For Indoor And Outdoor Positioning

GNSS (Global Navigation Satellite System) has become a key technical approach to get temporal and spatial related information. However, wireless signals of GNSS satellites always suffer from reverberation and obstruction in harsh environment and the number of satellites in view may not be enough to provide timing and positioning services we need. Nowadays people spend about 80% and 90% of their time indoors, thus the spatial related services should also expand from outdoor environment into indoor environment to meet their spatial correlated requirements, and how to provide high precision and seamless positioning services has become a question needed to be solved.SOP (Signal of Opportunity) refers to signal not special for providing navigation and positioning services, such as signals of mobile phone and wireless local area networks. With the development of technology of wireless communication and the construction of wireless city and digital city, there are more and more SOPs in our surrounding environment and the signal quality and strength of which are much better than that of GNSS, so the SOPs are becoming an effective way to solve the problems of positioning in harsh environment. Taking the consideration of disadvantages of GNSS positioning and advantages of SOPs in harsh environment, this thesis aims to research on some problems in indoor and outdoor positioning based on fusion of GNSS and SOPs, and the concrete contents are as follows:(1) Temporal datum and spatial datum with their unified usage in indoor and outdoor positioning are studied. UTC (Coordinated Universal Time) could be used as the temporal datum for positioning service. When it comes to the spatial datum, the choice relates to the specific positioning environments. Outdoors, earth-center earth-fixed coordinate system is always used as the spatial datum, while independent coordinate system is preferred indoors. With Gauss rectangular plan coordinate system, Gauss mapping and coordinate transformation could be used for datum transformation between indoor positioning and outdoor positioning.(2) Definition of symbol datum is made in this thesis, and means of expression for position information in this datum is also given. To meet the need of diversification for position information in location-based services, on the basis of conventional coordinate system, POI (Point of Interest) containing coordinate information and social contributes information may be used to define the symbol datum and more life-like positioning-about information can be obtained by spatial analysis in this datum.(3) In order to solve the positioning problem when there are not enough GNSS satellites in the light of sight, a WLAN/Wi-Fi assisted GNSS positioning method with fixed geodetic height is proposed. Firstly, the coarse two dimensional coordinates are obtained using Wi-Fi positioning. Secondly, final positions are derived by GNSS positioning with fixed geodetic height. A simulated experiment was carried out and the results showed that the stability and accuracy of final positions were much better than the coarse coordinates derived from Wi-Fi positioning, and the positioning accuracy correlated to the geometric distribution of GNSS satellites and the magnitude of bias of fixed geodetic height.(4) When the number of GNSS satellites used for poisoning is not sufficient, and for weakening the influence of the geometric distribution of satellites on GNSS positioning with fixed geodetic height, a WLAN/Wi-Fi assisted GNSS positioning method based on minimum range error algorithm is proposed. In this method, the coarse three dimensional coordinates are obtained using Wi-Fi positioning and fixed geodetic height, and then an optimization matching method based on coarse-coordinates-centered search grid is used to get the final position. The simulated experiment showed that, compared with the Wi-Fi positioning results, accuracy and stability of the final position derived from the proposed algorithm was improved, and this method can avoid the ill-conditioned design matrix of observation equation which is confronted in the WLAN/Wi-Fi assisted GNSS positioning method with fixed geodetic height.(5) Work on design of assisted information service system for the signals of opportunity based positioning is finished in this thesis. The system aims to provide some assisted information for users using signals of opportunity to get their positions. In order to make the assisted information more compatible and general, the two widely used international standards called RTCM SC- 104 and NMEA 0183 were expanded. All related information are coded according to the format of the expanded international standards and broadcasted via NTRIP (Networked Transport of RTCM via Internet Protocol). In this way, the traditional high precision GNSS poisoning and the signals of opportunity based positioning are combined together.(6) The spatial granularity and spatial scale of indoor and outdoor positioning are discussed, and the ubiquitous positioning service mode based on cooperation of different poisoning system is also researched and analyzed. The spatial granularity is reflected through the users' positioning requirements and it determines the accuracy of positioning results derived from positioning systems. The spatial scale determines the level of abstraction of position information of geographical entity, and the choice of positioning system should take account of the users' moving spatial scale. The spatial granularity and spatial scale can be used to analyze the users' positioning requirements in the specific environments, and function cooperation of different positioning systems can be an effective way to provide ubiquitous poisoning services.