The Sat Nav GPS, or Satellite Navigation Global Positioning System, consists of 24 satellites (plus a few spares) orbiting in space 12,500 miles above our earth. Each of these solar-powered, 2000lb satellites rotates the earth twice a day in an exact predetermined orbit, sending out radio signal data which can be picked up and analyzed by any GPS receiver.

In a process called triangulation, the GPS receiver can take the signals from 3 satellites and calculate its own position on earth to a great degree of accuracy. With the signal data from 4 or more satellites, the GPS receiver can also determine its 3D position on earth, ie  the altitude, as well as the latitude and longitude.

There are actually 3 satellite navigation systems in use around the world. The USA's GPS system named NAVSTAR with its network of 24 satellites is by far the most used and best known. Other systems are the European Galileo and the Russian GLONASS. China has its own system on the way too.

Originally, the US military developed the NAVSTAR system for its own use, but not long after made it available for civilian applications. The first of the GPS satellites was launched into orbit in 1978 and by 1994 the full system of 24 satellites was in place.

Today, the most common civilian use of sat nav is for car navigation. The computer in the car's GPS receiver can take the satellite data and compute many useful things for the traveler. It can interact with road map data to show your exact street position, and give directions to any other roads in its database.

Depending on your GPS receiver's capabilities, you may get information on petrol stations, speed camera locations, car parks (including if they have vacancies!), places of special interest, traffic jams and alternative routes, weather conditions, etc. Some models are equipped with a 'text-to-speech' function which allows you to keep your eyes on the road while it verbally guides you with instructions. This is a great safety feature which saves you from constantly having to check your progress on the screen.

It is important to always exercise caution when using GPS navigation. They are not infallible devices so they occasionally make mistakes.. or your road map data may be out of date. Always use common sense and never blindly trust your sat nav receiver.

Other Uses For GPS

Besides road navigation for automobiles, the Satellite Navigation Global Positioning System is indispensable now for marine and airline applications. Whereas once the stars were the navigators' 'landmarks' - today it is radio waves from satellites.

As GPS receivers have become smaller, more portable and more sophisticated, a whole new generation of applications has sprung up.

* Geocaching has become a popular new recreation. With a hand-held GPS receiver, and clues from various internet sites, people are participating in 'treasure hunts' all over the world.

* GPS pet collars are becoming common. If you are worried about a straying pet, a GPS collar can pinpoint its whereabouts at all times to a few meters.

* The tiny new GPS chips can help you keep an eye on your toddler too. As a bracelet, watch or charm,  or attached to the child's clothing - this can bring great peace of mind to a parent of wandering children.

* Golfing GPS system are now available. These small hand held devices give exact distances to the flag from any place on the course. They are legal too!

* GPS exercise monitors are proving very popular. They record the speed, distance traveled, distance to go to a set destination, and more. Great for walkers, runners, bikers etc.

The list goes on and on, and new applications are constantly being developed. Next time we'll go into greater detail of all the exciting new GPS products coming onto the market.

The portable GPS navigation receiver market is red hot! New models with impressive new features are constantly coming on the market.

Five brands in particular have become very popular thanks to their consistent top quality and/or pricing.

Garmin is at the head of that list as the best seller. Magellan GPS has been a great innovator over the years with many firsts on the market - including the 1st commercial handheld unit. The TomTom GPS units are well known and popular for their user-friendliness. The Mio GPS company is not as big a player as some of the others, but it has a very popular range of units covering the full spectrum of budgets.
Nextar is new to the market but has achieved rapid popularity for its very affordable pricing.