Portable Garmin GPS - Where did GPS Start

What a bonus it is when you get your new vehicle and it has a GPS system already installed, and with luck it's a portable Garmin GPS. Gone are the days when you have to fumble through the street directory as you're driving, or have to rely on someone else giving you spurious directions. Having a GPS is now second nature to many people who would be rendered lost, literally, and frantic without one.

Are you aware though of how they came into being? Not surprisingly, they were originally developed for military purposes, to keep track of ships, submarines, planes etc. but it obviously wasn't long before the commercial viability of the GPS for everyday use became apparent.

The GPS receiver as we know it relies on 24 operational satellites orbiting the earth at all times at a set distance of more than 12000 miles above the earth, although your portable garmin gps receiver only uses information from 4 of these satellites at any one time.

Every one of the 24 satellites orbits on a very precise line which ensures that your receiver is always in contact with at least 3 of the satellites. As your receivers clock needs to be synchronized withe the clocks in the three satellites it is receiving data from, this is the function of the signal from the 4th satellite in your quartet. Atomic clocks housed in the US Navy Observatory provide the amazingly accurate time line that is crucial for the GPS system to work effectively. All 24 of the orbiting GPS satellites is fitted with it's own atomic clock.

The portable Garmin GPS receiver has a chip installed which is pre-programmed with a log book or almanac giving the positions of each satellite at any given time in the future, so that the receiver knows where to search for the nearest satellites.The satellites also send out almanac information with their signal, so that the almanac of your navigation device is regularly updated.

The accuracy of a position determined with a GPS depends on the type of receiver. Most hand-held portable garmin GPS units have about 10-20 meter accuracy. Of course it has not always been this accurate in the past and there was an in-built reason for this. The first commercial receivers were specifically built with a timing error, on military 'advice', that limited their accuracy to around 100 meters. in 2000 though, this error was no longer deemed necessary and removed from new devices.

The portable Garmin GPS is as accurate, if not more so, than any comparable device. You can happily and safely use it to get you from A to B and even C via D without ever needing to ask directions again. I know as a guy that the only hurdle I now have to get over is that the lady giving me directions, really is right this time!

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Hank Absolom is a grocery delivery driver in LA. He swears by his Garmin GPS Nuvi 350 to get him from his depot to every drop-off on his route and says it has saved him over 90 mins. driving per day! Compare other GPS Systems here

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