bout as big as the proverbial stocking stuffer and priced at less than $100, Magellan Systems Corp.'s GPS Pioneer looks like a child's toy. It's actually a sophisticated navigation instrument that uses the Defense Department's Global Positioning System to pinpoint your location with satellite accuracy. Powered by a pair of AA batteries, the Pioneer opens up the world of GPS navigation to more people than ever before.
Besides telling you where you are, the system gives your current elevation, how fast you are moving, and the precise time. If you program in a few landmarks, it will tell you how far you are from each. And it can record your path, so you know how to get home.
I last looked at GPS systems in May, when Magellan's bottom-of-the-line GPS 2000 weighed 10 ounces, cost $150, and ran for roughly four hours on batteries. The Pioneer weighs 6 ounces and runs for nearly 24 hours on batteries. And it has a more sensitive receiver: I had no trouble picking up the GPS signal through the window from an Amtrak train or while walking around the city.
I like the Pioneer's waterproof case and easy-to-use interface, but the power button is too easy to press. I often found the unit was on when I took it out of my backpack. If you are going to take it hiking, be sure to pack a spare set of batteries.
Like all GPS receivers, the Pioneer works by listening for signals from the 26 GPS satellites that orbit the earth. The service is free. Theoretically, GPS receivers should have an accuracy of roughly 5 meters, or about 16 feet. But in order to prevent enemy nations from using US satellites to guide their missiles, the Pentagon introduces random errors into the signals. This is called ''selective availability,'' and it has the effect of reducing the accuracy to between 100 and 300 feet.
To help improve the quality of GPS in the United States, the Coast Guard operates a series of Differential GPS (DGPS) beacons, special radios that listen to the GPS signal, compute the error that the Department of Defense is introducing, and transmit a correction.
Using DGPS improves the accuracy dramatically. Don Meyer, a spokesman for California-based Magellan, a unit of Orbital Sciences Corp., says his company's receivers can approach accuracy of 15 feet using the system. To use DGPS you need a more expensive GPS receiver - one equipped with a data port - as well as a Differential Beacon Receiver ($495) and a $15 antenna from Radio Shack.
A pricier stocking stuffer is Magellan's NAV 6000 ($599.99). Besides the data port, this unit has a high-resolution LCD screen and a slot in the battery case that can accept a microchip that carries an electronic map. The $199 map cartridges are manufactured by C-MAP, a Cape Cod company. I have one that covers Southern New England: highways, recreational areas, waterways, and some political boundaries. I took my NAV 6000 out to a friend's barn on Martha's Vineyard and discovered that the hill he lives on is called Ridge Hill.
On the way back from my friend's house, I left the NAV 6000 on my dashboard. When I got home, the unit had drawn a little map showing my course. I hit a bump at one point and the NAV 6000 fell onto my Jeep's floor. The case got a little scuffed, but otherwise the unit was fine. That's because, unlike other makers of handheld electronic devices, Magellan mounts a tough plastic shield a few millimeters above its LCD screens, with a little air gap between the two.
The NAV 6000 also comes with a socket for an external antenna and a stand that lets you mount the unit on your dashboard. You can use the NAV 6000 without reading the owner's manual - one button labeled ''Map'' displays the map, while buttons labeled ''zoom in'' and ''zoom out'' let you change the scale. But if you do take the time to crack the instructions, you'll learn how to customize the unit's screens.
Unfortunately, while the NAV 6000 will tell you where you are, it usually can't tell you where you are going. That's because the C-MAP maps shows only highways, not residential streets. To get that database, you need to hook the NAV 6000 up to a laptop computer and run Magellan's Map 'N Track program ($99). The software will also work with Magellan's GPS 4000 XL ($249.95), which lacks its own cartographic database.
I've tried using a handheld GPS and a laptop in a car, but it's a bit difficult. What's more, I've had a few near-accidents because I was trying to click buttons on the GPS rather than watching the road. And GPS systems have a hard time tracking you in cities; the tall buildings get in the way of the satellite signals.
Specially built navigation systems, such as those manufactured by Rockwell and installed in some rental cars, are a better approach. I tried out the Hertz ''NeverLost'' system a few months ago and was stunned by the system's accuracy and the detail of its maps. The good news for consumers is that the Rockwell division that manufactures the Hertz system was sold to Magellan earlier this year, and the company plans to sell these systems to the public.
Magellan's Web site can be found at www.magellangps. com.
Technology writer Simson L. Garfinkel can be reached at plugged-in@simson.net.
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