GPS Overview Part 1 - Introduction
The original theory behind Location-Based Services - or
LBS - is to help you find out where you are or where something else is.
There are several ways of determining location, including GPS, cell
locations, triangulation and other methods.
This overview describes the history and workings of the Global
Positioning System (GPS), as well as its uses and the future for it.
The Global Positioning System (GPS) is a network of 24
Navstar satellites orbiting Earth at 11,000
miles. Originally established by the U.S. Department of Defence (DOD) at a
cost of about US$13 billion, access to GPS is free to all users, including
those in other countries. The system’s positioning and timing data are used
for a variety of applications, including air, land and sea navigation,
vehicle and vessel tracking, surveying and mapping, and asset and natural
resource management. With military accuracy restrictions partially lifted in
March 1996 and fully lifted in May 2000, GPS can now pinpoint the location of
objects as small as a penny anywhere on the earth’s surface.
The first GPS satellite was launched in 1978. The first
10 satellites were development satellites, called Block I. From 1989 to 1993,
23 production satellites, called Block II were launched. The launch of the 24th
satellite in 1994 completed the system. The DOD keeps 4 satellites in reserve
to replace any destroyed or defective satellites. The satellites are
positioned so that signals from six of them can be received nearly 100
percent of the time at any point on earth.
GPS provides specially coded satellite signals that can
be processed in a GPS receiver,
enabling the receiver to compute position, velocity and time. Basically GPS
works by using four GPS satellite signals to compute positions in three
dimensions (and the time offset) in the receiver clock. So by very accurately
measuring our distance from these satellites a user can triangulate their
position anywhere on earth.
GPS receivers have been miniaturised to just a few
integrated circuits and so are becoming very economical. And that makes the
technology accessible to virtually everyone. These days GPS is finding its
way into cars,
boats, planes, construction equipment, movie making gear, farm machinery,
even laptop computers. This report shows the various features of GPS and the
reasons why it may soon become almost as basic as the telephone.
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