Introduction

I. What is GPS?
A. History
B. Development
II. How Does GPS Work?
A. Satellites and Receivers
B. The Three Parts of GPS
III. Applications of GPS
A. Military
B. Civilian
Conclusion
The Global Positioning System
With the proliferation of satellite-based
defense systems and their continuing presence in
the media it makes us more aware of our national
defense. The United States is large, economically
strong and a sometimes tumultuous presence in the
global community. Although we may feel secure
because of our superior technology and defense
capabilities, our size and position in world
affairs can make us a target for some countries. We
can no longer be concerned with just our borders
and now what comes from the skies and the sea is
more of a threat than ever before. The United
States government had to develop a way to counter
these possible attacks and the Global Positioning
System (GPS) was conceived.


The Global Positioning System was initiated in
1973 by the Department of Defense (DOD). It was
developed by the the DOD because at a cost of over
twelve billion dollars the government had the
monetary resources to achieve these idealistic
goals. Since that time it has grown from one
satellite used strictly by the military to
twenty-six satellites that can be used by civilians
also. This satellite system is used to determine
the speed and position of an object anywhere in the
world within one hundred meters to mere millimeters
depending on the size and quality of user
equipment.(GPS JOINT PROGRAM OFFICE.

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ICD-GPS-200:GPS INTERFACE CONTROL DOCUMENT.)
The original purpose of GPS was to maintain a
strategic military advantage over our enemies.


Toward the end of the arms race the targeting of
ballistic missiles became so exact they could land
directly on an enemy missile silo and destroy any
missiles inside of it. The ability to take out your
enemies missiles from great distances had a major
effect on the balance of power. To maintain the
balance of power the United States government had
to develop a way to locate surfacing submarines in
a matter of minutes anywhere in the world. With the
use of satellites in orbit the Global Positioning
System was created.


GPS uses twenty-six satellites and ground
tracking stations around the world to compute
distances using time. This is done by finding the
difference between the time a signal is sent and
the time it is received. The satellites have atomic
clocks so the time is extremely accurate. The
receivers position is determined by using three
satellites, this is called
triangulation.(kAPLAN,eLLIOTT. UNDERSTANDING
GPS:PRINCPLES AND APPLICATIONS)
GPS is made up of three segments: space, control
and user. The space segment includes the satellites
and the rockets that launch them from Cape
Canaveral. The satellites are powered by solar
cells and continuously point their solar panels
toward the sun and their antennae toward earth. The
control segment includes the master control station
in Colorado and monitor stations around the world.


This segment makes sure orbits and clocks operate
within acceptable limits. The user segment includes
the equipment used by the military and civilians
who receive GPS signals. ( Kaplan, Elliott.


UNDERSTANDING GPS:PRINCIPLES AND APPLICATIONS)
The military applications of GPS are used in
fighters, bombers, helicopters, submarines and
soldiers gear. Wartime defense is now more
accurate and dependable than ever. While still the
most important aspect of this technology, GPS is
not used strictly for navigation anymore. Other
uses include but are not limited to: target
designation, air support, soldier rendezvous and
smart weapons. Smart bombs use GPS to receive
location information so they can guide themselves
to a preset target. This technology is a great
asset in battle as it basically casts a net over a
battlefield and can locate tanks, vehicles or even
soldiers who may be in immediate danger.


In the everyday world, GPS has also made life
easier and safer. Hikers and hunters can carry hand
held receivers in case they should get lost in the
wilderness. On-board navigation systems in
automobiles let drivers avoid congested freeways
and find better routes to destinations through
voice-activated user equipment. Drivers can also
make cellular calls using these GPS computers
should something happen to them in transit. Other
aspects of this technology are used in farming.


Maps can be created of the fields during harvest
and used the next season to plant and fertilize
areas that need more attention. This increases crop
production while reducing the use and expense of
fertilizers, pesticides and fuel which also helps
our environment. This process is called Precision
Farming. Another very important use of GPS is the
avoidance of in-flight collisions. Airlines are in
the process of equipping their airplanes with GPS
receivers. This will enable each aircraft to detect
other planes in the vicinity and make sure they
dont cross paths in the air. This is much more
accurate and reliable system than is currently
available and is sure to make the people flying in
these planes more comfortable and secure.


The Global Positioning System has grown
into a resource that goes far beyond the initial
design goals. These days scientists, farmers,
soldiers, pilots and delivery drivers are using GPS
in ways that make their jobs safer and more
productive. The benefits of GPS are not limited to
job related aspects alone. The future of this
technology is limitless and will change and develop
rapidly as new and varied applications are
introduced.


Bibliography
Kaplan, Elliott. Understanding GPS: Principles and
Applications. Boston: Artech house Publishers,
1996
Thompson, Steven D. An Introduction to GPS,
(Everymans Guide To Satellite Navigation.


ARINC Research Corporation, 1994
The Untold Story of CALCM: The Secret Weapon Used
in the Gulf War. GPS World January 1995 page
16
GPS Joint Program Office. ICD-GPS-200:GPS Interface
Control Document. ARINC Research Corporation.


Available On-line from United States Coast
Guard Navigation Center.


Dana, Peter H. GPS Users Overview. Available
on-line at
www.utexas.edu/depts/grg/gcraft/notes/gps/gps.h
tml
Checklist
Angela Grubbs