January/February 2006

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Spatial orientation plays a critical role in aviation, especially under conditions of instrument flight rules. The ability to detect the direction of an aircraft’s heading, the ground, an airfield, and approaching aircraft is particularly challenging at night or in stormy weather. This article describes ongoing work to develop a GPS/IMU-based head tracking system to provide 3D audio cues that can help pilots orient themselves in adverse circumstances.

U.S. military leaders asked a group of scientific and political experts to take a long, hard look at the Global Positioning System, its management, and its prospects in a changing GNSS world. They got an earful. Now it's up to Secretary of Defense Donald Rumsfeld to sort things out.

What a strange trip it's been for the world's leading global navigation satellite systems. Now a pioneer struggles to stay ahead, a former contender stages a comeback, and the new kid on the block puts some unexpected twists into an old plot.

After six years of deliberations and regional workshops, the United Nations has fostered the creation of an International Committee on GNSS to promote the benefits of space-based positioning, navigation, and timing — particularly in developing nations.

Although Galileo operates wholly under civil control, it does include encrypted signals, including those of the Public Regulated Service or PRS, which are broadcast near the new GPS military M-code signals at the L1 frequency. In light of a continuing interest in combined use of M-code and PRS, this article examines some of the technical issues surrounding the subject.

Part of the rationale for building additional GNSS systems, in addition to the motive of political sovereignty, is the argument that a single system is not able to meet all the requirements for use in challenging application environments such as large cities and mountainous terrain. In the end, our answer to the question of GNSS compatibility and interoperability also answers the question of whether GNSSes are complementary or competitive and mutually exclusive systems.

Slowly, steadily, but with an ever-growing momentum, GNSS-driven applications of accurate time and location are entering the popular imagination. Today, hundreds of millions of people are walking around with GPS receivers in their pockets — whether they know it or not. And literally billions are benefiting from the myriad uses to which the technology is being put.