You Are Here
Satellite navigation systems take a turn for the better
From the Print Edition:
Camilo Villegas, July/August 2006
It was a rain-spattered night in the City of Angels and I was behind the wheel, lost and alone in the kind of neighborhood where, if your tire blows out, you just keep riding on the rims. Each maybe-this-will-help turn just took me deeper into the heart of darkness, and the fuel tank was getting parched. Finally, somewhere between La Brea and the pits of hell, I remembered. I rummaged in the glove compartment and pinned my hopes on guidance from above. "Turn left in 100 yards," said an angelic female voice. I did as I was told. "Continue for one point five miles, then merge right onto Highway 101." I yielded to her firm but friendly entreaties until, at last, I maneuvered the rented Taurus into a parking spot at the Comfort Inn on North Highland. I gave my digital companion a grateful pat, unplugged her and took her back to my room, where I enjoyed a hard-earned minibar nightcap while she sucked AC from the outlet by the sink.
Yes, my friends, it's a scary world out there, but a satellite navigation system does help take the edge off when the going gets tough. The technology involved is fairly amazing stuff. Starting in 1978, the Department of Defense began launching a series of solar-powered satellites, each equipped with an atomic clock and a radio transmitter, into orbit. By 1994 the full complement was complete, 27 satellites covering the entire earth's surface, beaming information to GPS (Global Positioning System) receivers back on earth.
The satellites basically say "here's my name" and "here's the precise time where I'm flying." The GPS receiver on the ground includes its own accurate clock. By comparing the time the satellite sent its signal with the time that signal reaches the GPS receiver, the latter can figure out the exact distance between them (a pretty sharp bit of calculation, when you consider that radio signal travels at the speed of light).
So far so good, but that still doesn't tell me that I'm standing at the corner of Bowery and Delancey. For that you need to receive signals from three different satellites with three defined distances (the GPS receiver can pinpoint your position using triangulation). And with four signals, it can calculate your altitude, too. Those satellites are very far away (circling 12,000 miles overhead). They send out weak signals (just 20-50 watts, compared with 100,000 watts from your local FM radio station), yet a basic consumer-grade GPS can figure out your latitude and longitude anywhere on the globe within about 20 to 40 feet, and the professional models used by surveyors and such hone this accuracy down to about one centimeter. Of course, you have to be outdoors with a clear overhead view for this magic to occur—the low-power GPS radio signals can't penetrate into buildings.
Knowing where you are is a big deal. In fact, for those rugged souls who tromp into the wilderness with nothing but paper maps, protein bars and really expensive hiking boots, that's all they ask from a GPS unit, and there are plenty of inexpensive handheld devices to suit their needs. I, on the other hand, want to know not only where I am, but how the heck I can get where I'm going, which requires far more from my technological sidekick. For starters, built-in maps and a screen to read them on. Second, the artificial smarts to look at those maps and plot a turn-by-turn course from here to there. A synthetic voice to read the directions aloud (preferably without the note of disdain that creeps into my wife's voice when I'm lost) is also important so I can keep my eyes on the road. While it's not an absolute requirement, something called text-to-speech technology really helps. Instead of simply "Turn left in 50 yards, the navigation system can say "Turn left on Pine Drive in 50 yards"—a very useful clarification when entering a complex intersection at high speed.
Live traffic updates are the most intriguing recent addition to the navigational mix. Real-time traffic info is the killer app that will convince drivers who generally follow the same route every day to invest in a navigation system. Sure, you know the way, but real-time traffic info can tip you off about an accident on the highway you ordinarily use and, what's more, suggest an alternate route… in a perfect world.
Stuck here in 2006, real-time traffic is very much a work in progress. Its usefulness is limited by the spotty and slow system that reports congestion to a central command and then relays it to the public. I test-drove it in the New York area and sometimes found myself already stuck in traffic jams my handy dandy receiver had yet to tell me to avoid. Some systems use information delivered via XM satellite radio. Others rely on FM radio transmissions via the Clear Channel network. Each requires a monthly subscription charge (from $4 to $10 depending on the package) and covers only limited regions at this stage. The monitoring system is bound to improve, which will make it desirable, but the service has limited value at present.
I concentrated on portable navigation systems for this roundup, as opposed to systems built into the car dashboard (either purchased with your car or installed afterward). There's an undeniable appeal to a sleek built-in system that doesn't take up extra room, draws power from the car itself and automatically mutes the radio when it has something to say. On the other hand, I put a premium on the ability to move a nav system from car to car, accompanying my daughter if she's driving off to a far-flung friend's house or flying off in my briefcase when I'm headed for a rental car in a strange city.
Car navigation systems have improved dramatically since I first tried one several years ago. The receivers that pick up satellite signals are much more sensitive, making them better able to get a fix in an area with tall buildings or overhanging trees. These units used to require plug-in power at all times, from your car or an AC adapter (which was usually an extra-cost accessory)—if you wanted to figure out your itinerary the night before, you were out of luck. All of the systems reviewed below have internal batteries that last several hours, so you can dispense with the power cord altogether for most trips and preplan in peace. Portable units used to come with cumbersome clips that attached them precariously to ventilation system air ducts—today a suction-cup mount that sticks firmly to the car windshield is standard equipment. The information databases that help you find the nearest "Points of Interest" (POI)—ATM machines, hotels, gas stations, restaurants and the like—have been expanded dramatically. Some units I tested boasted listings for more than six million places, making navigating far from home much simpler.
Still, it's important to understand that, even when the nav system can pinpoint your location precisely, the information in the database will inevitably have some flaws. I found myself driving to bank branches that no longer exist or, more disconcerting, being told to make illegal turns. I also found while driving in familiar areas, the recommended route didn't always match the best route that a local might drive. Bottom line: you can't turn off your brain when you turn on the navigation system. That said, all of the systems have the ability to create a new route if you deviate from the originally plotted course, so even with a few extra turns, you will reach your destination without overwhelming aggravation. And that's well worth a few hundred dollars' investment.
You must be logged in to post a comment.