@CONFERENCE\{IMM2005-04218,
    author       = "A. B. O. Jensen and M. Zabic and H. M. Over{\o} and B. Ravn and O. A. Nielsen",
    title        = "Availability of {GNSS} for Road Pricing in Copenhagen",
    year         = "2005",
    keywords     = "{GNSS} {GPS} Galileo raytracing",
    pages        = "2951-2961",
    booktitle    = "Proceedings of the 18th International Technical Meeting of the Satellite Division of the Institute of Navigation{-ION} {GNSS} 2005",
    volume       = "",
    series       = "",
    editor       = "",
    publisher    = "The Institute of Navigation",
    organization = "",
    address      = "3975 University Drive, suite 390, Fairfax, {VA} 22030",
    note         = "Best Presentation Award",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/4218-full.html",
    abstract     = "Like most older cities, downtown Copenhagen is a net of narrow streets surrounded by tall old buildings and with no, or very limited, possibilities for changing the traffic corridors. During business hours the traffic congestion is intense, and the workforce in Copenhagen spend hours on the roads every day, stuck in slow moving traffic flows or traffic jam. Several means for regulating vehicle traffic flow exists, and various analyses and experiments have been carried out in a number of European Cities during the last five years as part of the PRoGRESS programme, sponsored by the {EU}.

In Denmark, Copenhagen participated in PRoGRESS with the {AKTA} project. The major part of the {AKTA} project was to equip 500 cars with {GPS} receivers. {GPS} positions were logged along with information on speed, number of satellites, {HDOP} etc. With this paper we present an analysis of the {GPS} data collected, with the purpose of evaluating whether stand alone {GPS} is feasible for operational road pricing in Copenhagen. 

The analyses show that the {GPS} satellite availability in the downtown streets is not sufficient to form the basis for an operational road pricing setup in Copenhagen. The narrow street canyons prevent a sufficient amount of satellite signals from reaching street level, and there are too many gabs in the position logs to implement a fair and reliable taxation scheme. The need for augmentation is evident, and with the advent of Galileo within a few years, it is relevant to investigate how integrated {GPS}/Galileo receivers will change the situation. 

With a {3D} city model of Copenhagen, a Galileo simulator, and a raytracing algorithm, an analysis of the {GNSS} availability in the streets of Copenhagen was carried out.  The analysis is focusing on the number of visible satellites and the {HDOP}. The results show that the satellite availability, given both by the number of visible satellites and by the {HDOP,} is slightly better with Galileo than with {GPS,} and the situation is considerably improved if {GPS} and Galileo are used in combination. The results also show, however,  that there will still be streets in downtown Copenhagen were the receiver–satellite geometry represented by the {HDOP} is not sufficient for reliable positioning during the full 24 hours of a day, even when combined {GPS-}Galileo receivers are introduced.
Finally the results of the simulations are compared with the analysis based on {GPS} data collected in situ during the {AKTA} project, and the comparison show that the results are basically identical, thus verifying that the simulation scenario is reasonable."
}