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Currently the U.S. and Russia have constellations of
satellites that transmit continuous signals that receivers
(typically called navigator devices) can use to determine
their locations. (A European system named Galileo is
under construction.) A receiver can triangulate its
position if there are at least 4 satellites in range.
The GPS satellites can provide 15 meter horizontal
location accuracy to civilian GPS receivers. The deliberate
degradation of the civilian signal to 100m accuracy
was recently stopped.
Handheld consumer GPS devices are now available for
under $100. Boats and aircraft have long used GPS postioning
and now there are systems also available for cars.
The signals are provided free (the satellites originally
were aimed for military use), although the European
Galileo system will charge for signals that provide
the highest precision.
The growth of the commercial GPS industry has begun
to accelerate as new applications and capabilities appear.
The total GPS industry now had revenues of about $12
billion per year as of 2002. (Economist Magazine - March
14, 2002).
- GPS
section offers lots more information on GPS applications
and commercial developments.
- Tracking
Systems - GPS and comsat based systems for tracking
trucks, railway cars, containers, etc.
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