The Global Positioning System (GPS) is a worldwide radio wave navigation system formed from a constellation of 24 satellites and their ground stations to determine accurate location and time. It was developed by the U.S. Department of Defense with the primary purpose of enhancing the effectiveness of U.S. and allied military forces. GPS is rapidly becoming an integral component of the emerging Global Information Infrastructure, with applications ranging from mapping and surveying to international air traffic management and global change research.
These days people from different walks of life are using GPS in ways that make their work more productive, safer, and sometimes even easier.
The real-world applications of GPS fall into five broad categories:
Location
The
first application of GPS is the determination of a
"position" or location. GPS is the first positioning
system to offer highly precise location data for
any point on the planet, in any weather.
Navigation
Navigation
is the process of getting something from one location to another.
GPS helps to determine exactly where we are, but sometimes important
to know how to get somewhere else. It was originally designed to
provide navigation information for ships and planes.
Tracking
Tracking
is the process of monitoring the movement of people and things as it
moves along. GPS used in effective fleet management.
Mapping
Mapping means creating maps of the world. It is a big world out there, and using GPS to survey and map it precisely saves time and money.
Timing
GPS used to disseminate precise time, time intervals, and frequency. It makes the job of "synchronizing our watches" easy and reliable.
GPS receivers integrate a
radio and a navigation computer and can receive the faint, twenty-watt
signals coming from the satellites. The computer uses these signals to
calculate the distance between the satellites and the receiver. With
this information, the computer can further calculate the position and
velocity of the receiver.
The number of satellites visible to a receiver constantly varies between
four and eleven according to time and location. Each satellite
broadcasts a number of unique spread-spectrum codes, but only one, the
Coarse Acquisition (C/A) code, is easily accessible for civilian use.
Code is effectively a timing signal synchronized to an international
time standard-Universal Coordinated Time (UCT).
