Ah, the lure of the open road in summer. You take time off work, hop in the car, roll the windows down, turn the radio up, push the pedal to the metal, and head for the highway. Then, while you're peeling the pickles off your fast-food cheeseburger, you miss your exit. So you take the next one, three miles later. But you can't get back to the highway from that exit, and you're forced to turn right when you want to go left. Before you know it, you're lost.

Can the global positioning system save you from such an ignominious fate? Perhaps: I've found that a GPS receiver keeps me on track and, in the event of a misstep, gets me back to where I need to be.

But as with most electronic gadgets, there are various types of GPS products aimed at different types of user and budget levels. This week I present a guide to help you determine which device is best for you.

At its most basic, a GPS receiver is an electronic instrument that pinpoints your current location on a map. GPS devices for consumers are generally available as add-on accessories for Palm OS and Pocket PC PDAs; as stand-alone devices used by hikers, urban explorers, and others; and as navigational systems built into high-end automobiles.

A few rental car agencies, most notably Hertz, provide in-car GPS navigational devices as an option. The Hertz NeverLost system is a color LCD panel that displays maps and allows you to enter information using on-screen buttons. Along with pinpointing your location, the Hertz NeverLost system provides turn-by-turn audio driving directions (to minimize driver distraction). When it's time to turn right, for instance, a gentle voice prompts you.

The GPS network of satellites was developed by the U.S. Department of Defense during the Cold War as a way to quickly pinpoint the precise locations of surfaced nuclear submarines, according to Trimble, a GPS developer. According to Trimble's Web site, the cost of developing the GPS was $12 billion. In other words, your parents' tax dollars paid for today's GPS infrastructure.

Before you shop for a GPS device, consider how often you end up in new cities or towns during the course of a year.

To me, the ideal candidate for a GPS device is someone who travels to unfamiliar areas at least five times a year and, while there, must find their way to several locations (such as a client's office, a convention center, a restaurant, and so on).

The frequent business traveler to unfamiliar lands has too much at stake not to consider a GPS receiver. For instance, years ago I became hopelessly lost en route to an interview with a CEO in Tampa, a city I knew nothing about. Needless to say, the executive was fuming when I finally arrived an hour late (this was in the days before cell phones or consumer GPS devices) and the interview was a bust.

The circumstances in which you'd use a GPS receiver should also play a role in your buying decision. Some examples:

Do you often drive by yourself? If so, you need a device that provides audible driving directions, so you can keep your eyes on the road. Example: Garmin International's StreetPilot III (see the "GPS Gallery" below for more details on this and other devices).

Do you often need to find your location on a map while walking? In that case, consider an add-on to a PDA (or a stand-alone handheld GPS device). Because they're small, the devices are easily carried around. Example: Mapopolis' GPS receivers for Palms and Pocket PCs.

Do you often travel by car with a notebook but only occasionally need help? Then a GPS accessory that works on your notebook may be just the ticket. Example: Navman GPS E Series for Notebooks, which connects to a portable computer via USB port.

Do you always drive your own car, or do you rent? If you make frequent business trips with your own wheels, consider investing in an in-car navigation system. They're expensive but could be worth the money. Some BMWs, Cadillacs, and other high-end automobiles offer navigation systems as options. On the other hand, if you often rent a car, consider booking a Hertz NeverLost-equipped vehicle. Or buy a GPS device that sits on the dashboard and can be moved from one car to another, such as the Garmin StreetPilot III.