- The Washington Times - Wednesday, June 15, 2005

Today, due to sheer gadget-fetishism on my part, we’re going to look at shirt-pocket GPS receivers (that’s Global Positioning Satellite). These have been around for a while but they have gotten so good lately that I’ve fallen in love with them.

They look like calculators, with screen and keyboard. They tell backpackers, boaters and motorists exactly (almost exactly, anyway) where they are on the face of the Earth. In fact, they do more. Lots more.

How they work: The Department of Defense maintains a constellation of 24 GPS satellites, putting up new ones when the old ones age. These transmit positioning signals that are picked up by GPS receivers. By measuring the travel time of the signal from the satellite to the receiver, the receiver calculates the distance to the satellite. Then, by triangulating signals from several satellites, the receiver can calculate its position.

How accurate are they? There are portable GPS systems with features such as Wide Area Augmentation System (WAAS) and Differential GPS that make them more accurate, sometimes, depending on where you are. But Garmin International Inc., a major maker of shirt-pocket units, says that its receivers are accurate to within 15 meters in normal GPS mode, improving to 3 meters with WAAS enabled.

Why are these gadgets really neat? Because the combination of accurate positioning, plus built-in computer memory and an accurate watch, makes it almost impossible to get lost.

A friend just got back from an expedition doing archaeological work in the featureless high desert of Peru. He said that after he parked his truck and walked more than half a mile, he could no longer see the vehicle and frequently couldn’t find it at the end of the day. With his shirt-pocket GPS receiver (it was a Magellan unit, available at www.magellangps.com/en/) he just “bookmarked” the location of the truck when he got out. Later he could look up the bookmark on the unit, which pointed an arrow in the direction of the truck.

“Used to be, to map a site you had to use surveying instruments. Now you just walk the perimeter with GPS in record mode and download the data into a computer. It’s so easy it feels like cheating,” he said.

Outdoorsmen have got to love these things. Can’t see land from your sailboat and aren’t sure just where to port it? No problem. Found a really good fishing hole in a trackless swamp? Sunken treasure in the Caribbean? Just bookmark it and you’ll have no trouble finding it another day.

A model highly recommended by backpacking friends who have used it is the eTrex Vista C from Garmin. This GPS receiver will remember the path you have taken during the day. Should you want to backtrack, it will point the way.

Because these units know what time it is as well as where you are, they can calculate not only the distance you have covered but the speed at which you have covered it.

I like the Garmin because I’ve seen it, I like the color screen, and I find the keyboard easy to use and the design intuitive. If you have thoughts of buying a GPS receiver, check the Magellan Web site as well as Trimble.com, as these are both major manufacturers and may offer something better suited to your needs. The Garmin goes for between $400 and $500. Less fancy models from various companies sell for not much over $100. I may get one, even if I only use it to navigate around the backyard.


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