GPS Route guidance

For the directionally challenged, there is help. No longer do you have to listen to your companion belittle your abilities as a navigator or swallow your pride by admitting that you're lost. Today's in-car navigation devices are just the thing to keep you on track during your travels, and they're ready for prime time. In this guide, we discuss the technology behind GPS and tell you what to look for when you're ready to make the purchase.

The biggest advantage that in-car GPS devices have over paper maps is the ability to create electronic routes, complete with turn-by-turn directions, and in most cases, voice-guided directions. Depending on your GPS unit's feature set, it may be necessary to plot a route on your PC before heading out on the highway, although most, if not all, current models contain enough memory and map storage for on-the-fly routing. Creating a route involves entering a destination and letting the system determine a route from your current location.

Almost all the of the high-end vehicle navigations systems utilize touch-screen technology to make entering destinations and addresses as easy as possible, and a few select models let you access the on-screen keyboard via a wireless remote control. Some of the newer (and more expensive) in-dash models now feature voice-activated input, such as the 2006 Honda Civic Hybrid, where you train the system to accept spoken commands. This is a trend that is also starting to show up in portable units, such as the TomTom GO 930.

Routes can be calculated any number of ways, depending on your preference. You can ask for the fastest or the shortest route and you can tell the system to avoid certain roads, such as toll roads and interstate highways. This is particularly helpful if you know that a stretch of road is under construction, or is closed for some reason.

Once the system has your starting point and your destination, it calculates the best route according to your specifications and displays it on a map, highlighting each segment of road along the way. The map view is typically a 2-D view, although most of the latest systems are capable of displaying 3-D and aerial map views. You can also view the directions in text with details such as distance between turns and estimated time of arrival based on your current traveling speed.

Ideally, the system is capable of giving voice-guided directions, which lets the driver concentrate on driving without having to glance at the screen. With voice directions, it's almost impossible to get lost or miss a turn because you are alerted of your next maneuver well before you actually have to make it. The voice prompt typically warns you of your next turn immediately after you've completed a maneuver, then again as you're heading towards the turn (to give you enough time to safely change lanes), then one more time as you approach the actual turn or exit ramp. Newer systems like the Magellan Maestro 4040 and the Garmin StreetPilot c580 feature text-to-speech functionality, which actually tells you the name of upcoming streets. If you still manage to miss the turn or deviate from the original route, the system will calculate a new route based on your present location.

Of course, an in-car navigator is only as good as its receiver, and since not all GPS systems are created equal, some are more accurate than others are. The same goes for mapping data and directions; a good system will have up-to-date maps that can differentiate between one-way streets, dead-ends, and so on. As a rule of thumb, GPS systems that use NAVTEQ or TeleAtlas digital maps are among the most accurate as for mapping detail.

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