G.P.S. didn’t always stand for Global Positioning System, you know.
In the beginning, it stood for the Grunting and Pointing System, used by cave men to indicate the nearest watering hole. By the horse-and-buggy era, G.P.S. had evolved into a different navigation technology: Guidance by Pony Sense.
In the automobile age, G.P.S. came to mean Grumbling by Peeved Spouse. ("Why won’t you just stop and ask?")
Today, G.P.S. is a beautiful thing. A receiver in your car can learn its own location from 24 government-owned satellites overhead — your tax dollars at work.
You're guided to a destination with colorful moving maps on a touch screen and an authoritative voice ("In 200 feet, turn right").
I went looking for G.P.S. models that fulfill three requirements. First, each must be tiny (about the size of an index card), self-contained and battery-operated, so you can take it hiking or biking when it’s not plugged into your car’s cigarette lighter.
Second, each must display live traffic and accident data — and offer to reroute you as necessary. (The traffic data is available mainly in big cities and on highways, and costs extra — usually $50 to $80 a year.)
And finally, each must pronounce actual street names — not just "Turn right," but "Turn right on South Maple Street." That feature makes an enormous difference when you're flying blind in a new town.
As it turns out, only the top models meet those criteria.
Each also plays music and photos; makes wireless connections to Bluetooth cellphones for hands-free calls; and offers a built-in database of United States and Canadian roads stored in memory. (Units that keep the data on hard drives are slower, more fragile and more power-hungry.)
Each receiver also knows about millions of points of interest: restaurants, cash machines, gas stations, parks, hospitals and so on. Most let you call one of these places (through a Bluetooth phone) with one tap.
Now, even these top-of-the-line units are imperfect; in a world where roads are constantly changing, a G.P.S. receiver is only as good as its most recent database update. But in general, these are absolutely incredible machines.
A Voice to Guide You on the Road
Cobra Nav One 4500 ($520). This is probably the chattiest G.P.S. unit ever made. "Now enter the street name," it says. "You don't need to add suffixes like 'east' or 'avenue'," it advises. And so on.
But to her credit, the first thing Ms. Chatty tells you is how to turn her off. And the truth is, these voice prompts make the Cobra infinitely easier to use than its rivals. It's like having a company rep in the passenger seat, explaining what each button does.
That, alas, is the Cobra's chief virtue. The navigation screen is pretty cluttered, and the animated "please wait" logo makes too many appearances, suggesting that the Nav One’s processor isn't quite up to the task.
The Cobra's feature list is shorter than its rivals', too; for example, the Cobra and Magellan are the only units here that can't play music and voice prompts through a clear, unused FM frequency on your radio (a feature that works great outside metropolitan areas).
Harman Kardon Guide + Play GPS 810 ($600). This intriguing unit comes with a toadstool-shaped control knob that attaches to a dashboard, console or steering wheel, and lets you control the G.P.S. unit wirelessly.
In other words, you don’t have to lean or reach to operate the touch screen. Since you can interact with portable models even while you're driving (unlike built-in car systems), you could argue that the wireless knob makes the Guide + Play just a little bit safer.
The G+P loses safety points, though, with its other unusual feature: it can play videos loaded from your computer. But you'll watch them only when you're parked, waiting to pick someone up — never while you’re driving. Right?
The software is clean and responsive. The navigation is generally smart; like its rivals, the G+P offers either an overhead map view (2-D) or an extremely helpful 3-D view. It’s like seeing the landscape from the cockpit of a helicopter.
Magellan Maestro 4250 ($450). Like any gadget in a car, G.P.S. receivers are a distraction, and therefore a safety risk. So it’s amazing that speech recognition didn’t arrive in these units sooner.
On the Magellan, it’s not much; you can say things like "Magellan, go home," "Magellan, nearest A.T.M." or "Magellan, nearest Italian restaurant." You have to speak loudly, and you have to speak close to the unit. But it's a start.
The Maestro’s price is the lowest of the bunch — not a bad feature. Neither is its built-in AAA database of restaurant, lodging and travel blurbs.
The screen display is excellent and the navigation is good, especially the magnified split-screen view that appears at each turn. You can choose which kinds of unfortunate traffic events you want brought to your attention: road work, slow traffic, stopped traffic, accidents and so on.
On the downside, the Magellan can be slow to compute routes, or recompute them when a wrong turn is made. And the maps aren’t as refined-looking as the TomTom's or Garmin's.
Garmin Nuvi 680 ($620). Garmin's top domestic model is smooth, fast and good-looking, showing the kind of polish you can achieve when you've been playing the G.P.S. game for years.
The screen is incredibly bright, with beautiful 2-D or 3-D maps. You have a choice of voices, including two with cute Australian accents.
The Nuvi can receive MSN Direct, the wireless data broadcast that Microsoft originally created for its wireless wristwatches. Once you've signed up ($50 a year, or $130 lifetime), traffic flow is indicated with color coding on the maps. Better yet, you also get weather, local movie showtimes and even local gas prices. It's pretty great to have all that right on your dashboard.
Nitpickers will note that on this unit you can’t exclude a particular road from your route, and the speaker is too weak when the road noise is loud.
TomTom GO 920T ($500). This top-of-the-line TomTom looks stunning, even before you turn it on. Its 3-D display is the most elegant available, with the smoothest animation and smartest layout.
A light sensor dims the screen at night; a speed sensor tracks your place even in tunnels; and an audio sensor cranks the voice volume when the road gets loud.
Then there's the speech recognition: Rather than fussing with a touch keyboard to input destinations, you can just speak them when prompted. ("Chicago. Riverside Lane. Two hundred.") You're on your way in seconds.
The Help Me screen is also ingenious. Its icons include "Where Am I?," "Walk to Help" (which guides you as you take the TomTom out of the car) and "Drive to Help" ("Nearest car repair," "Nearest hospital" and — my favorite — "Nearest dentist").
The 920T can get its traffic data either through a windshield wire antenna or via a Bluetooth cellphone with an Internet data plan. (If you use the antenna, you pay $60 a year for the data service; if you use the phone, the service is free for now, although TomTom says that it eventually plans to charge $25 a year.) And TomTom’s brilliant, fledgling map-sharing program lets you update your receiver’s maps with errors and updates reported by other customers.
The windshield suction cup isn’t as good as Garmin’s, and the voice lady consistently pronounces bridge as "branch." But overall, this receiver represents the high-tech state of the art.
The whizzy TomTom, the superbright Garmin and the more-limited Harman Kardon are all light-years more advanced than anything you can get preinstalled in your car. (Besides, buying one of these portables means you can move it between cars.) They completely transform the business of driving.
They're expensive, but they earn their keep by saving you the G.P.S. of getting lost: Guessing, Panicking and Swearing.
David Pogue is a columnist for the New York Times and contributor to CNBC. He can be emailed at: firstname.lastname@example.org.