January/February 2006

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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.

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.