Future trend
Satellites provide a better system of area
navigation than ground-based radio stations. In the 1980s the U.S. Department of
Defense developed a highly accurate satellite-based navigation system known as
the Global Positioning System, or GPS. GPS and other satellite navigation
systems provide highly accurate positioning information to anyone using an
appropriate receiver.
GPS-type systems
are so accurate that the FAA and its international counterpart, the
International Civil Aviation Organization (ICAO), have agreed that satellite
navigation will become the standard for international aviation navigation.
Satellite navigation provides adequate accuracy for in-flight navigation, but
will need to be improved if it is to guide aircraft during the more complex
landing procedure. Two systems have been developed and are planned for
installation by the FAA. One system, called the Wide Area Augmentation System (WAAS),
uses a satellite transmitter to send accuracy corrections to all aircraft
operating over the continental United States. The other, the Local Area
Augmentation System (LAAS), will be installed at airports to provide guidance
information that will allow automated aircraft landings in any type of weather.
One type of
instrument navigation that does not rely on radio or satellite transmissions is
inertial guidance. Inertial guidance uses mechanical or laser gyroscopes to
determine precisely an aircraft's direction of flight. When an inertial guidance
system has been programmed correctly, it can provide direction to any point in
the world. Although inertial guidance is fairly costly, its biggest advantage is
that it is a self-contained system, independent of either ground or space-based
transmitters.