EmailHandheld GPS vs. auto GPS
GPS receivers for the outdoor adventure market and for the automotive market are two different animals, although some can do double duty. Outdoor-oriented GPS receivers are made to resist the elements -- most are rubberized and water-resistant. Handheld GPS units are also meant to be lightweight and easy to hold with one hand. They have smaller screens than auto GPS receivers do, and the screen isn't always in color. Handheld GPS receivers also emphasize battery life. See our report on
Auto GPS receivers are portable, but you wouldn't want to take most of them camping. They aren't water-resistant, and because of their large screens, they're usually heavier than a handheld GPS (although the average weight is still less than half a pound). The big screen also saps battery life. Most auto GPS receivers can plug into a cigarette lighter. Auto GPS units come with highway maps and give audio directions. Handheld GPS receivers sometimes only come with the most basic maps, and some don't come with maps at all. Auto GPS receivers also come with a windshield or dash mount, while most handheld GPS units don't.
Other options for in-car navigation include a smartphone with built-in GPS reception (see our report on smartphones) or a Bluetooth-equipped laptop or PDA. Some PDAs come with an integrated GPS antenna, while others can accept an accessory receiver. Laptops have much larger screens than automotive GPS receivers, and they have abundant hard-drive space for map storage, but they aren't easily installed in your car, and they work best if you have either a copilot or software that gives audible directions. Otherwise, they are simply unsafe to use while driving.
Experts say aftermarket GPS units are better and cheaper than those that come factory installed in some new cars. Factory-installed GPS navigation systems can't be updated and can only be used in one car. However, factory-installed GPS units do have two advantages: they offer a clean, integrated installation, and they are much more difficult to steal than aftermarket auto GPS units. This report only covers aftermarket GPS receivers; the factory-installed units are rarely reviewed.
Auto GPS shopping tips
Here's what experts say to look for when considering an automotive GPS unit:
- For occasional use, a smartphone with a GPS app may suffice. Major GPS companies like Navigon, TeleNav and TomTom offer GPS apps for iPhone, BlackBerry, etc. in the $70 to $100 range that get good reviews. Some apps cost as little as $5 or $10 and work quite well in tests. But experts say dedicated auto GPS units are still more accurate and much easier to use. Good budget GPS units start at about $100.
- Quantity and quality of maps is critical. Furthermore, they must be current (or updateable), unless you will only drive in extremely mature cities such as New York or San Francisco. Some units can upload maps via a USB cable or a memory card. Internet-connected units from Garmin and TomTom can receive wireless, automatic updates.
- Automatic destination routing is a standard feature on any good car navigation GPS. With more sophisticated auto GPS models you can input several destinations and the unit will tell you the most efficient route to hit them all.
- Look for spoken street names. Instead of just giving an instruction to "turn left in 100 feet," models with text-to-speech can pronounce the street name ("turn left in 100 feet on Main Street"), giving you better information and reducing the need to look at the screen.
- Make sure the unit you select is capable of being mounted neatly and securely on your dashboard or windshield. Nearly all models come with the proper hardware. Experts point out that you must be able to mount the unit where it won't interfere with airbag deployment. All U.S. states now allow GPS units to be mounted on the windshield.
- Consider multimedia features. Many car GPS units play MP3s and can store photos. Most models play through integrated speakers, and some also offer an FM transmitter to play through your car stereo. However, tests find that FM transmitters don't work very well, and some models cannot play music and navigate at the same time.
- Decide if you want to get live traffic reports and alerts. FM/TMC, MSN Direct, Navteq, XM, Tele Atlas and Clear Channel offer live traffic information. Compatible GPS units use a built-in or external receiver -- or a Bluetooth-compatible phone -- to download this information and incorporate it into routing. Some Garmin nuvi models include a free lifetime traffic subscription; other GPS units usually require a separate yearly subscription. Check coverage, however. Each service is only available in a limited, though growing, number of major markets. MSN Direct service will cease on Jan. 1, 2012, due to a lack of subscriptions, Microsoft has announced.
- Make sure the screen size is appropriate for your eyesight and vehicle space. Most older and budget GPS models have 3.5-inch displays. Some budget models and most pricier units have 4.3-inch displays. Garmin offers some units with 5-inch displays.
- Consider an auto GPS unit with a large points-of-interest database (5 million or more). Points of interest include tourist attractions, hotels, restaurants, gas stations and ATMs. Some units allow you to download custom points of interest. Web-connected units offer unlimited searching via the Internet, rather than relying on a finite database.
- Weigh convenience features. A touch screen is now standard. Many units simplify text entry by only allowing you to type letters or names in the database. As you start to type, these units may also give you options to select. A few units allow voice commands, but experts say the Garmin nuvi 885T and nuvi 855 are the only GPS units that truly allow full voice operation.
How GPS works
The Global Positioning System (GPS) is a navigation technology that provides precise time and location data by using 24 Navigation Satellite Timing and Ranging (Navstar) satellites. Each satellite completes one orbit of the Earth every 12 hours. They are positioned at an altitude that allows them to cover the same ground once every 24 hours (minus four minutes).
Each satellite carries an extremely accurate atomic clock and transmits both its position and a time signal, which can be picked up by a GPS receiver. Since a GPS unit can receive data from multiple satellites, and since each satellite provides information that is appropriate to its own location and distance, the GPS unit performs the necessary calculations and arrives at a position fix accurate to within about 15 feet. Many factors can have an impact on accuracy, including atmospheric conditions, buildings, tunnels and heavy foliage. However, reviewers say that the latest receivers greatly minimize those issues.