Fall 2007

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GNSS and intertial navigation systems work fine for georeferencing images taken from aircraft usually free from satellite signal blockages, but can you make the same technologies work for you on the ground surrounded by terrain, foliage, and manmade structures? A North American remote sensing company has brought LIDAR technology down to earth with a GPS/INS-aided scanning system.

Europe's Galileo program continues to struggle through a difficult passage as it looks ahead to crucial meetings of the European Union (EU) transport, economic, and heads of state meeting November and December. The lingering death last spring of the public-private partnership (PPP) threw the program back into the political crucible that has always proved more arduous than the technical challenges.  The political discussion revolves around three different issues: financing, deployment, and governance of the system. Somewhat surprisingly, the third may prove the most substantive.

In a down-to-earth design somewhat reminiscent of the automatic dependent surveillance-broadcast (ADS-B) system being implemented in the U.S. airspace, system developers in Switzerland have outfitted a fleet of buses on a private, but narrow and mountainous road system, with combined GPS, GPRS communications, and portable navigation device displays.

The emergence of increasingly sophisticated GNSS signal processing techniques over the past 20 years is dramatically increasing the computational load on GNSS receivers. These techniques include new methods for acquiring and tracking a wide variety of second-generation signal structures, advanced multipath mitigation techniques, and the development of high-sensitivity receivers for reliable operation indoors and in urban canyons. Full story to be posted on November 15. 

The effects of RF interference on GNSS signal acquisition, tracking, and positioning accuracy have been studied extensively. In the United States, a national program is underway to identify and mitigate interference and jamming of GPS. However, the practical significance of interference for precise timing and synchronization is less well understood. In this article, laboratory test results reveal how two kinds of interference affect GPS signal reception and timing.

One feature that distinguishes Galileo from other GNSS systems is the Public Regulated Service or PRS, an encrypted signal that will be used by European governmental agencies, including police, emergency services, and, potentially, military services. This article discusses the need for and applications of the service, drawing on information from the PACIFIC project (PRS application concept involving future interested customers.)

We have an abiding trust, it seems, in the constancy of time. Amid this welter of transience, it's nice to think about those steady little increments of time, like the gentle susurrus of creation itself. . . Too bad it ain't so.