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E. Mok, G. Retscher, L. Xia:
"Investigation of Seamless Indoor and Outdoor Positioning Integrateing WiFi and GNSS";
accepted as talk for: XXIII International FIG 2006 Congress, Munich, Germany; 2006-10-08 - 2006-10-13; in: "XXIII International FIG 2006 Congress", (2006), 15 pages.

Location-Based Services (LBS) cover a wide spectrum of applications including fleet management, travel aids, location identification, emergency services and vehicle navigation. Applications of this service can be further extended if reliable and reasonably accurate 3-dimensional positional information of a mobile device can be determined seamlessly in both indoor and outdoor environments. Current geolocation methods for LBS may be classified as GNSS-based, cellular network-based, or their combinations. GNSS-based methods rely very much on the satellite visibility and the receiver-satellite geometry. This can be very problematic in dense high rise urban environments and when transferring to indoor environment. Especially in Hong Kong the urban canyon will affect very much the reception of the GNSS signals. Moreover positioning in the indoor/outdoor transition area would experience signal quality and signal reception problems, if GNSS alone systems are employed. The authors have proposed the integration of GNSS with wireless positioning techniques (Mok and Xia, 2006; Xia et al., 2006), and a fingerprinting positioning method based on WiFi signal strength observations has been tested with results analyzed (Retscher et al., 2006). Further developments have been made on signal strength to distance conversion of WiFi data for integration with GNSS and other range data sources. Recent test results in the outdoor area are presented in this paper.