Cheat Sheet

GPS For Dummies

From GPS For Dummies, 2nd Edition by Joel McNamara

If you're really good at getting lost, a GPS device can be your best co-pilot. And even if you're good with directions but just want to know where you are at all times, a GPS unit can offer accurate information on where you are on the planet. GPS manufacturers make devices to help you navigate in all types of vehicles whether you're on land, sea, air, or your own two feet.

Must-Have Features for a Handheld GPS

If you're happiest in the great outdoors, a handheld GPS device may make you even happier. Use a GPS unit to help with your personal navigation needs whether you're boating, hiking, geocaching, or doing any other outdoor activity. The following table offers recommended features to help you choose the right GPS receiver for your purposes:

Activity Useful Features in a GPS Device
Hiking, mountain biking, cross-country skiing Altimeter/barometer
Electronic compass
Sunrise/sunset table
Uploadable topographic maps
Geocaching Electronic compass
Geocache database
Uploadable topographic maps
Hunting Hunting and fishing calendar
Sunrise/sunset table
Uploadable topographic maps
Fishing Fishing calendar
Floats
Saltwater tide table
Sunrise/sunset table
Waterproof
Boating (inland and offshore) External power supply
Floats
NMEA output (for autopilots)
Saltwater tide table
Sunrise/sunset table
Uploadable nautical charts
Waterproof
Canoeing, kayaking (inland and coastal) Floats
Saltwater tide table
Sunrise/sunset table
Uploadable nautical charts and topographic maps
Waterproof
4x4ing, motorcycling, ATVing Electronic compass
External power supply
Uploadable topographic maps
Flying External power supply
Jeppesen database
WAAS
Mapping, data collection Area calculation
Differential GPS
External antenna
Helix versus patch antenna
Large number of waypoints and tracks
WAAS
Caving, scuba diving, visiting art museums Sorry, you're out of luck! You need a clear view of the sky for a GPS receiver to work.

How GPS Modes Affect Accuracy

The accuracy of your GPS unit can vary depending on whether you set the mode to make use of differential GPS (DGPS), which augments satellite information with ground-based signals; a wide area augmentation system (WAAS) developed by the Federal Aviation Administration for more accurate air navigation; or go without selective availability (SA). The following table shows how accurate you can expect your GPS unit to be in each mode:

GPS Mode Distance in Feet Distance in Meters
GPS without SA 49 15
GPS with DGPS 10–16 3–5
GPS with WAAS 10 3

Popular GPS Manufacturers

When you can download a GPS app to your phone, you know GPS has gone global in more than just name (GPS = global positioning system. Get it?). To help you explore some of the GPS makers out there, the following table offers links to some of the more prominent manufacturers and shows whether they make handheld or automotive devices or both.

Company Handheld Automotive
DeLorme X
Garmin X X
Lowrance X X
Magellan X X
Mio X
Navigon X
TomTom X

Even if a company doesn’t manufacture a handheld GPS unit, it most likely offers an app you can download to your mobile device.

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