Handheld 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 handheld GPS units for more information.
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 GPS-enabled smartphone in
conjunction with an appropriate GPS app (see our report on GPS apps).
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 in the $30 to
$100 range that get good reviews on iPhones, BlackBerrys and other smartphones.
Some apps cost as little as $3 for a month of turn-by-turn directions and
work quite well in tests. But experts say dedicated auto GPS units are
still more accurate and much easier to use. Budget GPS units from major
brands start under $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.
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.
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.
- Decide if you want to get live traffic reports and
GPS units use a built-in or external receiver or a Bluetooth-compatible
phone to download this information and incorporate it into routing. Many
now include a free lifetime traffic subscription; others require a separate
yearly subscription. Check coverage, however. Each service is only available
in a limited, though growing, number of major markets. One traffic service,
MSN Direct, 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. Some older and budget GPS models
have 3.5-inch displays. Pricier units have 4.3-inch, 5-inch or bigger
- Auto GPS units usually include 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 this feature doesn't always work well in tests.
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.