For the Directionally Challenged, A Satellite to Keep the Car on Course

Giving directions should be simple. Count the traffic lights, estimate the mileage, toss in a couple of landmarks, and drivers are on their way.

The problem, as we all know, is that it's far more complicated than that. Enthusiastic sidewalk strollers, suddenly called on for directional expertise, recall a key landmark as green, not yellow. Or they count two traffic lights between you and your destination instead of the actual five. Worse, they forget that those last two streets you're supposed to turn down are one-way - going in the wrong direction.

Now a new wave of automotive satellite navigation systems, based on those long used in boats, promises to make navigating a little easier.

Guidestar, a Global Positioning Satellite (GPS) systems - currently available only from Oldsmobile and only in certain metropolitan areas - are a $2,500 factory option. They are also being developed for the aftermarket for pre-owned cars. And in a sign of things to come, this summer the Olympic organizing committee in Atlanta will test out systems capable of receiving real-time traffic information.

The Guidestar mounts on the dashboard and gives the driver directions to the next turn, to the freeway entrance, and all the way to a final destination.

The device keeps an eye on you by taking signals from four satellites to triangulate a position on the globe. It compares this with directional signals from a car-mounted gyroscope and the car's odometer, then plots all this against a map encoded on a computer disk in the trunk.

Despite all the sophisticated behind-the-scenes technology, the system is easy to use. After reading a safety warning about driving while looking at the dashboard screen, you simply decide whether you want to select from a preprogrammed list of attractions (including amusement parks, shopping centers, cash machines, and, of course, a list of local Oldsmobile dealers), a particular street address, an intersection, or a list of the system's 10 most-recent destinations.

If you choose "intersection," for example, it asks for a town, then gives a list of all the streets in that town. A four-way cursor pad allows you to move through the menu. After you've selected your first street, the menu lists all the streets that intersect it. Next choose whether you want the shortest time route, the route with the most freeway travel, or the route that avoids freeways. Press "enter" and the system produces a highlighted line on a map to start the trip.

Drivers can choose between displaying a map or turn-by-turn directions. The map can zoom in and out. And either way the system voices the directions.

The mapping is immensely detailed: In small residential neighborhoods, it knows whether to tell the driver to bear right or turn right on streets that could leave a human navigator befuddled.

But the downside of such detail is that accuracy sometimes suffers. In one local town, Fairway Circle was listed as Fairview Circle, though the street was properly located on the Guidestar's electronic map.

And while it knew of a barrier across a street that prevents left turns, its solution was to navigate to the end of the block and make a U-turn. Technically, a U-turn was legal in this spot, and the directions exhort you, "Please make a LEGAL U-turn." But it didn't account for the difficulty of such a maneuver at that intersection.

Another problem is the Guidestar's timing. When it's working right, it sounds an alert - "right turn approaching" - a few seconds before a turn, followed by two beeps when it's time to turn. But often the timing is off. Sometimes it comes so early that you end up ignoring it. Sometimes it's so late that if you haven't made the turn yet, you're going to whiz right by it.

These are all small quibbles with a huge system. Collectively, however, they can make a driver doubt whether the Guidestar's directions are always right. And you may end up questioning whether a navigator that can still get you lost - albeit only occasionally - is worth the hefty price. For most Americans who drive the same roads back and forth every day, the answer may well be no.

But as more of the country appears on GPS maps, the system will become useful for more vacation travelers as well as those who are new to an area, or whose work regularly takes them into unfamiliar territory.

What would make it better on a day-to-day basis is the ability to spot traffic jams and navigate around them - as drivers in Atlanta will be able to do during the summer Olympics.

The Atlanta Intelligent Traffic Systems showcase will use video cameras and traffic radar to monitor major roads and transmit the information via FM radio to GPS systems. Roads with 50-m.p.h. traffic would appear green and 30-m.p.h. yellow, for instance.

So far, only eight major regions of the US have been mapped in detail: a corridor from Atlanta to Miami; Boston; Washington-Baltimore; New York; the Midwest including Chicago, Indianapolis, and Detroit; Las Vegas, Los Angeles, and the San Francisco Bay Area. A cross-country map of major highways is also available.

The Boston map had plenty of detail in the city and all of the suburbs within commuting distance, but got less precise - fewer residential streets and secondary roads that could cut time off a trip - the farther out one drove.

Navigation Technologies, of Sunnyvale, Calif., produces the maps and is working on other cities including Denver, Phoenix, and Seattle. Updates will be available every six months.

A computer card with a map of each city slides into a slot in the trunk. Each card costs about $400, according to Bob Borsherts, a vice president of Zexel USA Corp., which makes the Guidestar.