All You Need to Know About GPS

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All You Need to Know About GPS

Jayesh Limaye, Jun 15, 2010 1300 hrs IST

Find out how GPS has evolved over the years

Man has always been an explorer, always traveling and migrating in search of new and better places to dwell. In early history, they used the sun, moon, heavenly bodies and constellations to determine the location and the way to their destination, but that is not a foolproof method because it is useless with an overcast sky. They used the magnetic compass, but that can only help you determine the magnetic directions which get distorted as you move towards the magnetic poles of the earth. They also used landmarks, but these were not possible to be used in the sea or desert. The GPS system available today bypasses all these problems and makes sure that you will never be lost anywhere on this planet.

Image courtesy: CompassRoseGeocoin.com

GPS or Global Positioning System is something that we take for granted today. Rather than being limited to GPS receivers, you find them in many other electronic gadgets such as mobile phones. It is a technology that allows you to pinpoint your location anywhere on Earth. And the cool thing is that you only have to pay for the GPS device while the service is free. But there is a lot more to this technology than just that and we will give you some idea about how it really works. But first we shall give you some background information.

Brief history

It all started in the early 1960s with land-based MOSAIC navigation system meant for military purposes and then the first satellite-based navigational system, TIMATION satellite, launched in 1967. With several more GPS satellites being launched, it was found that they were incompatible with each other. Consequently, the Department of Defense of the US government directed the services to unify their systems in 1973, which later evolved into the NAVSTAR satellite system. The first wave of GPS satellites, as we know today, began with the first launch taking place in 1978 and continued till 1985. The GPS system we use today is based on the second wave known as Block II satellites, consisting of 24 satellites that were launched between 1989 and 1994. There are three more satellites in this system, which remain in standby mode to start working if any of the working satellites fail. This system is run by the US government's Department of Defense (DoD) and the service has been made available for free to everyone.

These satellites revolve around the Earth at an altitude of 19,300 km and are timed such that at least four of them are accessible above the horizon at any given point of time. These circle the Earth twice a day in a very precise orbit. Initially these were meant mainly for military purposes, so signals for civilian GPS equipment was deliberately deteriorated thus leading to a lower accuracy. This has been removed in two phases, first in 1983 when the GPS service was made available for free for everyone, and finally in 2000 when it was ratified that civilian GPS receivers could use the same signals used by the military. Currently the GPS can pinpoint your location to within 15 meters. A new fleet of 30 satellites is soon going to replace these old satellites as a massive upgrade. A further new satellite system will be launched this year, which will increase the resolution to within a meter, but that will only be for military purposes.