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G. Liu, K. Zhang, F. Wu, L. Densley, G. Retscher:
"Characterisation of Current and Future GNSS Performance in Urban Canyons Using a High Quality 3-D Urban Model of Melbourne, Australia";
Journal of Applied Geodesy, 3 (2009), 1; 15 - 24.

Global Navigation Satellite System (GNSS) is a critical space-borne geospatial infrastructure providing essential positioning supports to a range of location-sensitive applications. GNSS is currently dominated by the US Global Positioning System (GPS) constellation, and is expected to offer over one hundred satellites in the next decade, support better positioning provision in terms of availability, accuracy, reliability and integrity, and consequently enable us to view more satellites with better geometric configuration at a given location and time, obtain increased positioning accuracy, and enjoy much improved availability and continuity of navigation support. However, GNSS performance in 3-D urban environments is problematic because GNSS signals are either completely blocked or severely degraded by high-rising geographic features like buildings.

The aim of this study is to gain an in-depth understanding of the changing spatial patterns of GNSS performance, measured by the number of visible satellites (NVS) and position dilution-of-precision (PDOP), in the urban canyons of Melbourne, Australia. The methodology used includes the following steps: (1) determination of the dynamic orbital positions of current and future GNSS satellites; (2) development of a 3-D urban model of high geometric quality for Melbourne Central Business District (CBD); (3) evaluation of GNSS performance for every specified location in the urban canyons; and (4) visualisation and characterisation of the dynamic spatial patterns of GNSS performances in the urban canyons. As expected, the study shows that the integration of the GPS and Galileo constellations results in higher availability and stronger geometry, leading to significant improvement of GNSS performance in urban canyons of Melbourne CBD. Some conclusions are drawn and further research currently undertaken is also outlined.

Project Head Georg Gartner:
Ubiquitäre Kartographie für Fußgängernavigation