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is comprised of 24 satellites (launched
and maintained by the military) that are
in continuous orbit 12,000 miles above the
earth. Using geometry, the intersecting
signals from three of these satellites can
pinpoint exact locations, and, by incorporating
the additional dynamic of time (each satellite
has an atomic clock on board) even moving
targets benefit from this location-tracking
system. The initial military application
was to use GPS as a surgical strike weapon
to minimize collateral damage to non-target
and civilian areas. Since GPS provides instant
location information enabling users to ascertain
where they are at any time anywhere in the
world, an additional benefit ensured that
everyone in a battlefield area was operating
from the same map from different locations.
In recent news,
U.S. Air Force pilot Scott O'Grady provided
the most dramatic use of GPS. American forces
rescued him after he was shot down behind
enemy lines in Bosnia in 1995. By using
a handheld GPS unit, he was able to determine
his exact position and radio it to rescuers
before hostile forces could capture him.
Though military uses are seen as essential,
it is in the civilian market where the broad
possibilities of GPS are being realized.
It has the potential to help people with
a range of location-specific activities,
such as finding their way around, tracking
their loved ones or getting emergency assistance.
GPS systems are currently being embedded
in many consumer applications such as cellular
phones, PDAs and car navigation systems.
Prototypes are being tested in portable
entertainment systems, personal/child locators
and watches. To date, over 3,000,000 devices
have been sold and 250,000 more are sold
every month with retail prices ranging from
$100 to $375 each.
GPS technology has
also been utilized in ships and marine vessels
for many years, allowing captains and navigators
to ascertain specific depth, landmark and
location information. Today, fire trucks,
police cars and ambulances are starting
to use GPS in a number of U.S. cities. The
San Jose based non-profit "Outreach" program
depends on GPS linked to computers to keep
track of its fleet of 160 vans carrying
disabled people to 2,000 appointments a
day. Some airlines are using GPS routinely
for navigation on over-water flights and
GPS will be the key in redesigning the nation's
air traffic control system to permit greater
flexibility and efficiency. Besides airborne
experiments, researchers at Stanford University
are developing a combination GPS/robotics
system on tractors for use by farmers bent
on increasing accuracy of their plowing
and in decreasing labor costs. By October
2001, all emergency response services will
be required to carry GPS locator services.
Other applications include car navigation
systems, asset trackers and fleet management.
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