How does GPS work?

GPS measures the satellite signals in proximity to your location.  The GPS receiver absolutely needs to know where it is! This happens by receiving signals from a minimum of three satellites. If it wants elevation, then a fourth satellite needs to come into play.

Next, is the high end math; GPS locks onto a position and uses trigonometry to calculate its position.  This is measured in latitude and longitude. From that point, as long as it stays locked onto your location, it can provide the  speed, distance and that most valued of all things; a map to your destination.

What is the signal accuracy of GPS?

GPS signal accuracy is approximately 50 feet. But some systems go beyond this range.

Ground stations help GPS systems achieve an accuracy greater than 50 feet. WAAS (Wide Area Augmentation System) correct satellite orbital errors. With 25 ground stations in the U.S., WAAS calculates and transmits the corrected data to fixed-position satellites.  WAAS-enabled GPS receivers reach accuracies of 10 feet or less.

DGPS (Differential GPS) also has a correction method with its network of towers. DGPS systems achieve an accuracy of between 10 and 20 feet, but the downside is that these systems require an antenna to receive the corrected signal.

What options are there for a GPS system?

You can either choose a dedicated GPS receiver with displays, or a receiver that works in conjunction with your PDA or notebook computer.  At the lower end, dedicated receivers with displays show the location and basic maps. Others at the higher end offer downloadable capability so you can receive more sophisticated map configurations from a PC.

Pocket PCs, Palm OS devices and notebook computers also offer GPS receivers combined with mapping programs. GPS devices come built into some PDA mounts offered by Akron and Seidio.

Bluetooth GPS Receiver

The Bluetooth GPS Receiver is a stand alone receiver that can communicate with a Pocket PC or Smartphone. To use the GPS receiver with your Windows Mobile device it needs to have Bluetooth capability, or you can simply add the receiver to the unit with a CF or SDIO Bluetooth card.

You don't have to be exactly near your GPS receiver to use it. This is what is really cool about this receiver. It's very flexible too. You can place it within 30 meters of your other Bluetooth devices and still have full GPS functionality.  Even more surprising...it can actually produce a map and location details while inside a clothing item or in a container.

It's convenient too. Before you leave for a trip, you can input where you want to go and have it all mapped out when you depart for your new destination.

Consider these factors when selecting a GPS system:

1. Watch out for lost signals. The GPS signal with a satellite could conceivably get lost in rough or remote terrain, like in a canyon or forest. This can be minimized with a system that continuously monitors 12 satellites.

2. Is the GPS system programmable?  What is the data package like? Is it cost-effective?

3. What is the power supply like? Some in-car systems come with their own batteries, while others are dependent on the car itself.

4. Pay attention to interface. Some GPS interfaces run better than others. Find out about their performance from tech journals and colleagues.

5. Look at how the maps and directions are displayed. Do you like the presentation? Is it easy to navigate?

GPS - Gets you on track

Think of GPS as a modern take on that classic refrain heard by car passengers everywhere,"Just ask for directions." Only now, you can ask your very own GPS system without worrying about getting lost.

About the Author

Jarred Lowe is a reporter based in Atlantic City. He's on the look out for mobile devices to enhance his productivity. Jarred's reviewed countless sites on the net, but always turns to the one run by Bob Caldwell. His website, as he says, cuts to the chase and has valued information on: Bluetooth cell phone deals -

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