The technology behind GPS
is relatively simple. A constellation of 24
satellites orbiting 11,000 miles above the earth
emits signals to receivers on earth. By measuring
the travel time of a signal transmitted from
each satellite, a receiver can calculate its
distance from that satellite. Satellite positions
are used by a receiver as precise reference
points to determine the location of the receiver.
When receiving the signals from at least four
satellites, a GPS receiver can determine latitude,
longitude, altitude, and time.
In 1989 the Department of
Defense (DoD) launched the first production
series of GPS satellites. This effort was the
initial step in revolutionizing the way we find
our location on earth. The 24 satellite system
was declared operational by the DoD on December
8, 1993. A similar declaration was made by the
Federal Aviation Administration (FAA) in February
1994 regarding the civil operational status
of GPS.
 The
overall objective of the FAA is to support the
operational use of satellite navigation for
all civil aviation needs including departure
operations, terminal, oceanic, en route, non-precision
and precision approaches, auto-landing, and
surface navigation. Some of the incremental
steps to achieve this goal have already occurred,
many are currently underway, and more are planned
for the near future.
The international community
can expect many benefits from satellite navigation
(GPS and its augmentations) including:
- Increased landing capacity
down to Category III precision approach service
to all runways and airports for all aircraft
types
- Improved safety with
reduced separation minimums resulting in increased
system capacity and capabilities
- Increased flexibility
to implement accurate area navigation by using
efficient, optimized, user-preferred flight
paths
- Improved ground and cockpit
situational awareness to reduce runway incursions
- Significant reductions
in aircraft operating costs
- Accurate position reporting
to enable uniform high-quality worldwide air
traffic management
- Consolidation of navigation
functions into a single satellite-based system
thereby enabling the potential phase-out of
older navigation aids at substantial savings.
Additionally, the FAA is
striving to enhance existing relations with
other civil aviation authorities and appropriate
organizations to create a seamless, worldwide
satellite-based navigation system. Such a system
will permit the use of a single piece of equipment
to support aviation navigation on a global basis.
Furthermore, it will provide the foundation
for future communications, navigation, and surveillance
systems and increase safety for carriers and
passengers internationally.
In furtherance of international
acceptance of GPS, on March 29, 1996, the President
of the United States officially reiterated the
U.S. commitment to continue the broadcast of
GPS signals on a worldwide basis free of charges
for the foreseeable future. The President also
made a promise to discontinue the use of selective
availability (SA) by the year 2006.
In January 1999, as a direct
result of the benefits brought about by GPS,
Vice President Gore announced that the U.S.
would begin a GPS modernization to further extend
the systems capability. This modernization would
include two additional GPS signals to enhance
the civilian and commercial service.
On May 1, 2000 the President
announced that effective immediately, the use
of SA would be discontinued. This will result
in accuracies up to ten times more accurate
than previously possible. All users worldwide
will benefit from these commitments.
Although GPS and its augmentations
can provide major benefits for navigation, especially
for the civil aviation community, there are
many steps that must be taken to implement this
technology. Standards and procedures development,
facility preparation, training, international
cooperation, and many other activities play
a critical role in bringing these systems into
operational use. Based on the capability of
GPS, the FAA has charted a course for the future
and is working to build a new navigation capability--one
that will guide our Nation's Airspace System
into the 21st century.
For futher information regarding
GPS, please contact:
GPS Product Team, AND-730
800 Independence Avenue, SW
Washington, DC 20591
Fax: 202-493-5031 |
