When people get in my car, I’m often asked whether it’s worth getting a GPS.

There are five big advantages that all GPS units have over paper maps and print outs from Mapquest and Google Maps:

• They will tell you when to make each turn. You don’t have to try to drive and read at the same time. Voice prompts tell you that a turn is coming and when to make it.
• If you miss a turn, the GPS will automatically recalculate directions based on your new location.
• The GPS unit will tell you what street you’re currently on. It’s great at night, when you can’t make out street signs. It is also especially helpful in confusing cities like Washington, D.C., Boston and San Francisco, where streets make weird turns or have seemingly randomly change names.
• If you decide to make a pit stop or find yourself running low on gas, they can all help you find the nearest restaurant, gas station or other business.
• The GPS will continually calculate how far you have to go and estimate the time until you arrive. If you can train the kids to look at the screen, you may never have to here “Are we there yet?”

Newer systems are incorporating live traffic data, allowing you to see traffic congestion ahead.

I’ve got several GPS devices: the GPS built into my Acura, a Garmin iQue and my cellphone, a Samsung A900.

The specifics will vary from device to device, but the general themes should apply across a category. I left out after-market installed units because they don’t offer any significant advantages over portable units.

In-car navigation systems

In-car systems have been around for years, but only in the last few years have they been introduced in more mainstream models. Marketing of nav systems has been ramped up as well.

Advantages

A big screen and integration with the cars other components are the key selling features. The 8″ screen in my Acura’s nav system is larger than any portable navigation device I’ve seen and way bigger than any cell phone I’d want to carry. It’s centrally placed and more legible in sunlight than other screens. The big screen offers another advantage: many systems have touch screens, making it easier to enter addresses.

The system is also integrated with the car’s speech recognition system. I can say commands like “Go home.” Sensors in the car provide additional data to the GPS, which (in theory) provide more accuracy. For example, a gyroscope tells the GPS when I’m making a turn.

And It Looks Really Cool.

Disadvantages

The biggest disadvantage is the cost. Most OEM nav systems are expensive – around $2,000. Updates are expensive, too. The update DVD for my Acura is $180, more than some of the cheaper PNDs. (And Acura’s DVDs are among the cheaper ones.) Car manufacturers typically issue new DVDs once a year, so the data may not be as accurate as those on cell-phone based systems.

Portable navigation devices

PNDs come from companies like Garmin, Magellan, TomTom and Mio. Prices on PNDs have plummeted in the last 6 months, with many solid performers now in the $200-$400 range. At the same time, manufacturers have been packing in feature after feature. PNDs like the Nuvi 660 can also serve as MP3 players, photo viewers and Bluetooth handsfree kits.

Did you miss the TomTom or Garmin ad blitz over the holidays? PNDs were also featured heavily in Black Friday ads.

Advantages

Compared with OEM systems, they’re a fraction of the price. They’re portable, so you can take them with you when you travel. I take my iQue with me whenever I rent a car. It gives me more freedom to take detours, knowing that I can always get back on track. PNDs typically have moderate sized touch screens, making it easy to see directions and enter data. The additional features, like the MP3 player and Bluetooth support can fill in other technology gaps. Data updates will be cheaper than OEM systems.

Disadvantages

The screens aren’t as big as the in-car systems. You also have to find a place to put them and have the cable running to your car’s power port.

Cell-phone based navigation

All of the major U.S. wireless carriers are offering GPS applications for capable cell phones. This usually involves downloading special software to your phone and paying for a data plan and navigation service.

Advantages

If you have a capable phone, you don’t have any upfront hardware cost. For about $10/month (plus data plan charges of $10-$30 a month), you can access a navigation system. You can take it from car to car, which is great for rental cars.

The data can be fresher than those in in-car systems. But just because you’ve got a live connection doesn’t mean the data is up-to-the-minute. Vendors of map and place data don’t update that frequently. You don’t have to pay anything beyond the monthly fee for updates.

Some systems provide ancillary data. On TeleNav, you can see prices at gas stations near your location.

And only cell-phone based GPS units can remind you where you parked your car.

Disadvantages

If you’re in an area where there’s no wireless data coverage, you might also be without a navigation system or maps. If you’re on Cingular or Nextel, this means large swaths of the country. The screens on cell phones are much smaller than on in-car systems or PNDs, so you’ll have less information on where you’re going. You’ll have to rely more on the voice prompts. If you’re not already subscribed to a data plan with your carrier, the annual cost is likely to exceed the cost of a PND.

Conclusion

Back to the original question. A couple of years ago, I would have said they’re not worth it. With the plummeting prices and increasing features, I think now is a good time to make the jump for anyone who does a fair amount of driving to new places. (Or in confusing places like DC.)

If you have a cell phone that is capable of running the nav software, it’s worth trying to see if you can deal with the small screen. If not, I’d opt for a PND. Given the cost, it’s hard to recommend a factory-installed unit.

See more of my writings on satellite navigation and gps.