May/June 2006

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There are lots of radio signals out there carrying modernized GNSS navigation messages of crucial importance to users and product designers. The authors of this article use RF monitoring technologies to capture and characterize tehse new signals in space from GPS, GLONASS, Galileo, and Beidou.

Ground tracking networks typically calculate GNSS orbits based on differences between the ground stations’ precisely known locations and the ranging signals received from the satellites. However, researchers also can use another method of precise orbit determination: satellite laser ranging. This article from authors at the UK Space Geodesy Facility describes the technique and the first results from tracking the Galileo spacecraft now in orbit.

Someday, coordinates will be part of every product and process in our lives, says GPS innovator Karen Van Dyke of the Volpe Transportation Systems Center. As one of the engineers working towards that goal, she uses GNSS to make the air transportation infrastructure more reliable, less vulnerable, and easier to monitor.

General aviation pilots often find themselves caught between a desire to keep equipment costs low and yet ensure redundancy in case of failure of a critical flight instrument. This article describes the implementation and test of a low-cost, GPS-based backup attitude indicator that relies on a $150 GPS receiver board, a popular PDA and an algorithm originally developed at MIT.

An ever-increasing number of mobile handsets come equipped with GPS and some with inertial sensors. However, these single-frequency units do not exploit the higher accuracy possible with real-time kinematic (RTK) techniques. Now a group of Nokia researchers are developing a software-only RTK solution using the hardware and wireless connections already existing in mobile phones.

In an industrious and cooperative surge of activity, we have seen three sets of draft specifications reach fruition in the last few weeks: publication of a joint recommendation for design of new civil signals on GPS and Galileo, the Galileo Interface Control Document, and the GPS L1C interface specification.

This article introduces the multiplexed binary offset carrier (MBOC) spreading modulation recently recommended by the GPS-Galileo Working Group on Interoperability and Compatibility for adoption by Europe’s Galileo program for its Open Service (OS) signal at L1 frequency, and also by the United States for its modernized GPS L1 Civil (L1C) signal. The article provides information on the history, motivation, and construction of MBOC signals. It then shows various performance characteristics and summarizes their status in Galileo and GPS signal design.