Global positioning system
Our ancestors used to work extremely hard to protect
themselves from getting lost in this mysterious world.
They used to erect monumental landmarks, study
conventional land maps and of course they used to mark
the stars in the night sky.
But today it is very easy to know one's position. You
just only have to get a pocket-sized gadget that will
make you know your exact position on this earth at any
given moment. The system of knowing one's exact position
on this earth is known as 'Global Positioning System'.
If anyone has a Global Positioning System (GPS)
receiver, and if the sky remains clear, then no way can
he gets lost on this earth.
Of note is that this pocket-sized gadget, the Global
Positioning System receiver, is quite expensive and it
also involves a fair amount of technical ingenuity.
GPS is specially a Satellite Navigation System that
helps in tracking our exact location with the help of
satellites. The Global Positioning System is mainly
funded and controlled by the U.S Department of Defense
(DOD). The system was primarily designed for the
operation of U. S. military. But there are also many
civil users of GPS across the globe. The Global
Positioning System provides some special satellite
signals which are then processed in the GPS receiver.
These GPS receiver's not only track the exact location,
but can also compute velocity and time.
The positions can even be computed in three
dimensional views with the help of four GPS satellite
signals. The Space Segment of the Global Positioning
System consists of the GPS satellites. These satellites
send radio signals from space which are received by the
GPS receiver.
There are more than 24 operational and 3 extras (in
case one fails) GPS satellites that moves round the
Earth every 12 hours.
The control of the Global Positioning System consists
of different tracking stations that are located across
the world. These monitoring stations help in tracking
signals from those Space Vehicles which are continuously
orbiting the earth. The Space Vehicles transmit
microwave carrier signals. The users of the Global
Positioning System have GPS receivers that convert the
satellite signals which estimate position, velocity and
time. Four satellites are required to track the three
dimensional location and time. The primary function of
Global Positioning System is the navigation in three
dimensions. The Navigation receivers are used for
aircraft, ships, and ground vehicles and sometimes for
personal use as well.
With GPS receivers, precise positioning of any
location can be done. The Global Positioning system is
based on a simple mathematical calculation that operates
through a process called Trilateration. In order to make
the simple mathematical calculation the GPS receiver
should know two things.
++ One is the location of the place to be traced by
at least three satellites.
++ Secondly, is the distance between the where the
receiver is located and each of those Space Vehicles.
All units have multiple receivers, and can pick up
signals from several GPS satellites at a same time.
These radio waves are electromagnetic energy that
travels at the speed of light.
The civil users across the world are allowed to use
the Standard Positioning Service without any kind of
charge or restrictions.