If you are going to rely on a GPS device on a driving trip, it's important to know about the abilities and limitations of the technology and the device.
In interviews, Rich Owings, author of "GPS Mapping: Make Your Own Maps" and operator of GPSTracklog.com, and other GPS experts offered these insights:
Explore before you go. Become comfortable with the unit before leaving for your destination. Discover all the features you might want to use on the road and explore all on-screen menus. Many GPS devices are intuitive, so you may never need to break out the owner's manual. But if you do, just don't do it when you're driving at 70 mph.
Know and obey the law. It may not be a good idea to use a GPS device while driving, but it's not illegal in California. State law, however, does prohibit attaching the receiver to your windshield with a suction or other mount.
Trust but verify. Based on his experience using GPS devices in many areas of the U.S., Owings thinks the systems are accurate more than 95% of the time, but says a little skepticism can be healthy. If your route doesn't look or feel right, it may not be. If you have any questions about the route your GPS has selected for you, zoom out so you can see the entire route or preview the turn sequence. Information about points of interest may be outdated; call ahead to make sure restaurants or other attractions are open or in business.
They may not work everywhere. Urban canyons can play havoc with GPS reception, causing you to lose your signal. Newer units have greatly improved reception, so this may not be the problem it once was.
If you use a portable GPS device, make sure it is fully charged. Take extra batteries and a recharger to plug into the car's power outlet.
Download maps if you can. Ask the manufacturer when the maps in your unit were most recently updated. If the model you are using allows, download current maps before you leave.
Enter your destination before you turn on the car. And resist the temptation to read the map while driving. A study by Virginia Tech, in Blacksburg, found that drivers who take long glances away from the road at the wrong moment are twice as likely to get into a crash or to nearly crash. Use GPS devices that provide turn-by-turn voice prompts that alert you far enough in advance so you can prepare.
Don't panic if you miss a turn. Most GPS units will automatically recalculate a new route so you can get back on course.
Take a paper map of the area you plan to cover, just in case. Depending on the features of your GPS unit, a traditional map can give you a "big picture" overview of your route and alert you to possible side trips or detours you may not have considered.
— Edward Segal