HOW GPS NAVIGATION SYSTEMS WORK

The Global Positioning System has been around for some time already. The prototype Block-1 GPS was launched February of 1978 for military use only. In 1983 President Ronald Reagan declared that the GPS system will be available for civilian use after it was completed. Satellites were first made by the Rockwell International and now by Lockheed Martin. And then by 1993 the GPS was then fully operational, and the next year all 24 satellites were then in orbit. By November 2004 tests for assisted-GPS systems for mobile phones have been successful. This was done by QUALCOMM, a research and development company focusing on wireless telecommunications. By 2005, another modernized GPS satellite was launched into orbit, transmitting a second civilian signal to augment user operation.

GPS Navigation System Use

The GPS system has three main operations. The space segment refers to the satellites currently in orbit. The control segment consists of the ground operations that maintain and update the satellites above. This is done by the US Air Force in different stations. Then lastly there's the user segment of the GPS system which is composed of the user and their GPS devices on the ground.

The satellites transmit a navigational message continuously at 50bps, giving time, an ephemeris that is updated every 2 hours and valid for 4 hours, giving the satellite its own orbit and broadcasted every 30 seconds; and an almanac that is composed of a rough orbit and status for every space vehicle in the constellation.

The World Geodetic System WGS84 system is responsible for calculating the coordinates using the precise time and position of the satellites in range. The ability to measure the difference in time by transmission is the key to calculating the location by GPS. Satellites are armed with atomic clocks while the receivers are equipped with sturdy crystal-oscillator clocks that get updated by transmissions from the satellites. By measuring the distance of the receiver with four satellites and knowing the intersection of these, the receiver can then calculate its own location.

GPS System and its Accuracy

There are occasional glitches in the GPS navigation system. For improving accuracy you would need a higher chip-rate signal. The high frequency signal can get up to 30 centimeters accuracy. Glitches can result from electronic errors, ephemeris and clock errors, and atmospheric effects from passing through Earth's electrically charged ionosphere. Despite these minimal errors that may occur, the GPS system has undoubtedly been considered a very relevant and reliable technology available for us today.