Mar 25 2010
Is GPS accurate?
What is GPS?
GPS or the Global Positioning system is formed with about 24 satellites which are located in the orbit by the United States’s Department of Defense. GPS functions in any weather condition, 24 hours a day, any where in the world without subscription fee and set up charge. GPS satellites revolve around earth in a very accurate orbit two times a day, transmitting information via signals to the earth.
The way GPS works
The GPS receivers on the earth fetches the signals to triangulate user’s exact position. Basically, the GPS receiver analysis the time a signal was sent to the satellite with the time it received the signal. The difference in time indicate the distance of the satellite. The receiver along with the distance measurement from other satellites determines exactly the user’s location and displays it on the electronic map of the unit.
To track movement and calculate latitude and longitude position, ie the 2D position, the GPS receiver must lock at least three satellite signals. Similarly, to determine 3D position, ie latitude, longitude and altitude, the receiver must lock four or more than four satellite views. Once the position of the user is determined, the GPS receiver can track other information such as trip distance, speed, bearing,sunrise and sunset time, distance to destination and more.
Modern GPS receivers equipping parallel multi channel design makes it extremely accurate. As on date 12 parallel channel receivers when first tuned on lock satellites strongly even in dense or urban cities. Certain factors like atmosphere and other source can cause error, affecting accuracy of the GPS receivers. Recent GPS receivers having WAAS- Wide Area Augmentation System can improve accuracy in less than 3 meters on average.
How accurate is GPS?
Better accuracy is achieved also through Differential GPS, DGPS that can correct GPS signal in about five meters. The system of DGPS comprises network of towers receiving GPS signals and retransmit the corrected signls using Beacon transmitter. On the other side the user must also posses a Beacon receiver and antenna to their GPS for receiving the correct signal.
The GPS space segment consist of 24 satellites that are orbiting above us apart 12000 miles. The satellites travel at a speed of about 7000 miles an hour. Powered by solar energy, the GPS satellites possess on board batteries for back up to keep them running during solar eclipse.
