stands for Global Positioning System. It is a globally available
space-based radio navigation technology which allows any user to
determine his/her position anywhere on this planet with a high degree
of accuracy. The system owes its existence to the U.S. Government,
which has completely funded its development, deployment and
maintenance. The technology was originally meant for military use, but
was later adopted for the general public.
The system consists of a constellation of 24 satellites, in medium
earth orbits (MEO), with their controlling ground stations and the
end-user terminals. The satellites use triangulation (more correctly
trilateration) technique to pinpoint the location of a user terminal
on earth. Ideally three satellites are required to locate a point on
the earth's surface, but to take care of timing errors a fourth
satellite is required. The controlling ground stations are required to
maintain the satellites in their proper orbits and to monitor and
correct any changes in their operation. GPS is relatively accurate
(around 10 meters). But to attain higher accuracy something called as
Differential GPS (DGPS) is used. DGPS uses a stationary point of
reference on earth, whose position is accurately known, to locate a
GPS terminal with greater accuracy than just GPS.
GPS based Wireless Embedded systems :
One can develop applications on
GPS kit which gives you the details about the your location.
Applications like Navigation, trekking etc can be built. Most cars to
hit the road now come with GPS kits integrated with road-maps to plot
routes to user destinations. GPS can also be integrated with GSM, CDMA
and other similar technologies in order to get more functionalities
like Location Based Services (LBS).