Find your location through GPS!!
The Global Positioning System (GPS) is a satellite navigation system that helps in locating a place on the earth.
What is GPS?
The GPS is actually a constellation of 27 Earth-orbiting satellites. In this, 24 Satellite Vehicles are in operation and the three are extras ready to work in case any one fails. GPS is owned and operated by the United States Government under the Department of Defense (DoD). The US President Ronald Reagan issued a directive making GPS freely available for civilian use, once it was sufficiently developed, for a common good. The GPS is considered a dual-use technology, meaning it has significant military and civilian applications. The first satellite for GPS was launched in 1989 and the 24th one was in 1994. GPS became fully operational in 1995. Bradford Parkinson, Roger L Easton and Ivan A Getting are credited with inventing this technology.
How GPS works?
Each of the 24 solar-powered satellites circles the globe at about 12,000 miles (19,300 km). They make two complete rotations every day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites "visible" in the sky. The four satellites are not evenly spaced (90 degrees) apart within each orbit. In general terms, the angular difference between satellites in each orbit is 30, 105, 120, and 105
degrees apart which sum to 360 degrees. The Satellite Vehicles orbit at an altitude of approximately 20,200 km at an orbital radius of approximately 26,600 km. Each one makes two complete orbits each day, repeating the same ground track each day. This means that the four Vehicles are visible from one spot for a few hours each day.
The flight paths of the satellites are tracked by U.S. Air Force monitoring stations in various locations around the world including Hawaii, Kwajalein, Atoll, Diego Garcia, Colorado, and Cape Canaveral along with shared monitor stations operating in England, Argentina, Ecuador, Bahrain, Australia and Washington DC.
GPS on finger tips
Today, the GPS receivers come in a variety of formats - from devices integrated into cars, phones, and watches. A GPS receiver calculates its position by precisely timing the signals sent by GPS satellites high above the Earth. Each satellite continually transmits messages that indicate the time of the message transmitted and the satellite position at time of message transmission.
A GPS receiver's job is to locate four or more of these satellites, figure out the distance between each and use this information to deduce its own location. This operation is based on a simple mathematical principle called ‘ Trilateration’.