The Global Positioning System (GPS) is the only fully functional Global
Navigation Satellite System that enables a GPS receiver to determine its
location, speed, direction, and time with the help of precise microwave signals.
It was developed by the United States Department of Defense, and was christened
officially as NAVSTAR GPS. Generally GPS is widely used around the globe as a
useful tool for map-making, land surveying, commerce, and scientific uses. It is
also an ingredient product in the scientific study of earthquakes, and
synchronization of telecommunications networks. It is through three or more than
three GPS satellites, the GPS calculates position.
Generally, GPS is divided into three major segments; mainly space segment
(SS), control segment (CS), and a user segment (US). To calculate the position
by a GPS receiver, it requires the current time, the position of the satellite
and the measured delay of the received signal. The position accuracy is
basically dependent on the satellite position and signal delay. With the help of
higher-chiprate P(Y) signal, position accuracy can be improved. Assuming the
same 1% bit time accuracy, the high frequency P(Y) signal results in accuracy of
about 30 centimeters.
Definitely, the atmospheric conditions play an important role in the speed of
GPS signals. Any inconsistency in the atmospheric condition can affect the speed
of the signals as they pass through the Earth's atmosphere and ionosphere can
affect the speed of them as they pass through the Earth's atmosphere and
ionosphere.
It was in the days of cold war that the US decided to develop GPS. The
launching of Sputnik by the Soviet Union motivated NASA for the development of
this project to trace the movements of the satellite Sputnik which later started
using for civilian purposes. In the present days the purposes of GPS ranges from
path finding for drivers to gathering of information on climatic
conditions.
