'The Global Positioning System (GPS) tells you where you are on Earth.

It's eleven o'clock ... do you know where your kids are? Would you like to? One way to track them would be to have a GPS receiver installed in the car! The GPS, or Global Positioning System, is one of the hottest technologies around, and no wonder. Consider these diverse uses:

Minnesota scientists use GPS to study movements and feeding habits of deer.
Surveyors used GPS to measure how the buildings shifted after the bombing in Oklahoma City.
GPS help settle property disputes between land owners.
Marine archaeologists use GPS to guide research vessels hunting for shipwrecks.
GPS data has revealed that Mt. Everest is getting taller! '

The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS.

GPS or Global Positioning System is a network of orbiting satellites that send precise details of their position in space back to earth. The signals are obtained by GPS receivers, such as navigation devices and are used to calculate the exact position, speed and time at the vehicles location. GPS is well-known for its military uses and was first developed by the US to aid in its global intelligence efforts at the height of the Cold War. Ever since the early 1980s, however, the GPS has been freely available to anyone with a GPS receiver. Airlines, shipping companies, trucking firms, and drivers everywhere use the GPS system to track vehicles, follow the best route to get them from A to B in the shortest possible time.

When I first wrote this article back in 2002, consumer grade GPS was very new, very expensive and very rare! Consequently most of those who chose to invest in GPS hardware had a vested interest in discovering how this marvel of technology worked. Back in 2001 when map based GPS navigation first arrived, new users could not believe that the system was fee free with no service plan and no contract, what was the catch they all asked? And so the seed of an idea that became this explanation was born.

6 years on GPS is mainstream, a commodity item that is no longer amazing or to be marveled at. We just open the box, switch on and use it with little thought to the technology that drives it. But it is still worth explaining how a small black box sat on your dashboard or held in your hand can know where you are anywhere on the surface of the planet to an accuracy of about 10m for consumer grade and 10mm for survey grade devices! That device on your dash is receiving a signal from a satellite orbiting above you at an altitude of over 11,000 miles! Not bad for a device that is not connected to a 2m dish!

With the help of A-GPS, the GPS (Global Positioning System) technology has been brought to your cell phones too. Let us understand what it is and how it works.

A-GPS is an acronym for Assisted Global Positioning System. It addresses signal and network problems by using assistance from other services. Such technology in your cell phone can help you in various ways like tracking your current location, receiving turn-by-turn direction instructions, location based tracking, etc. The working of a GPS and an AGPS is similar apart from this minor detail. Let us first understand how GPS signals are received and monitored.