How To Buy a GPS Unit

Because GPS (Global Position System) units are used in a wide range of industries many brands, models and features are available. However, most units suitable for outdoor use are similar in size, cost, and complexity to a cell phone. Here's some help to get you pointed in the right direction.

• How GPS works
• Types of GPS receiver units
• Functions and features

How GPS works

Global Position Systems units are a powerful technical tool in an easy-to-use interface.

• These units communicate with a network of satellites providing world-wide coverage.
• The satellites broadcast signals that your receiver uses to triangulate your position to within 100 feet.

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Types of GPS receiver units

Before you decide to buy a unit, consider what you want to do with it.

• Portable (hand-held)
• The compact and versatile design of these units allow them to be used for hiking, camping, hunting, and virtually any other activity that requires navigation assistance.
• Mounted
• Designed for use inside a vehicle.
• The larger size allows some of them to store more information (built-in maps) than hand-held units.
• Chartplotter
• Designed for marine use to help you navigate bodies of water.
• Often include additional marine features such as water depth, water temperature and tide prediction tables.
• Often used with fishfinders.
• GPS Software Systems
• Designed for use with portable computers or PDA's to turn the unit into a fully functional GPS.
• Requires a compatible operating system.
• GPS Fitness Systems
• Provides distance and rate of speed data to track your workouts
• Allows you easily navigate to desired locations
• Allows you to map your favorite routes

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Functions and features

• Waypoints
• The eastern and northern coordinates that describe a particular position on the globe
• A waypoint can be a trailhead, campsite, rock formation, or a series of points on a featureless landscape
• Route mapping
• Creates a set of waypoints for an area you plan to visit
• Especially useful for trips to unfamiliar places
• Routes
• An ordered series of waypoints. When following a route, the GPS selects each waypoint.
• Some units generate waypoints and automatically create a route as you travel, a handy feature if you end up having to backtrack in bad weather or darkness
• Altimeters
• Indicate altitude, or feet above sea level
• Very handy when hiking through mountainous terrain or when referring to a topological map
• Antennae configuration / number of satellites
• External antennas can often be manipulated to improve reception
• Optional plug-in antennas are handy for use in cars or boats, since they allow the unit to pick up signals in places (such as under a metal car roof) that satellite signals usually can't penetrate
• Built-in antennas are protected from breakage, and can communicate with up to 12 satellites
• More satellites translate to more accurate positioning, faster updates and better reception
• Connectivity
• A GPS unit can be made more useful via connections to a computer or another GPS unit. Most computer and computer accessory retailers carry the cable and software you will need to take advantage of these features.
• In addition to easy back-up, sorting, and additional mapping capabilities, connectivity allows you to share exact information on where you're going or have been with someone else
• Size
• For backcountry use or when extra load weight is a concern, you may opt for a smaller, lighter model
• If you will be using the unit in complicated outdoor terrain and/or urban locales, a larger unit with a bigger screen may be preferable
• Battery life and extra weight are related. The more batteries a unit carries, the longer its life and the heavier its weight. For long trips, the extra weight may be worth extended battery life.
• Most GPS units are equipped with a lithium battery backup memory function so information won't be lost when batteries die
• Weatherproofness
• While most receivers are built to withstand some exposure to rain and snow, they probably won't fare well if submerged in a lake or river
• A beefier, and consequently heavier, casing means better weatherproofing
• A carrying case is a useful accessory, and can extend your unit's life span
• Screen size
• The display screen should be easy to read in a variety of light conditions
• Illuminated screens are especially useful for nighttime and low-light situations
• Color vs. black & white
• Usually based on personal preference.
• Color screens are often easier to read in nighttime and low-light conditions
• Memory
• In general, the more storage space, the larger the memory, the more room a unit has for waypoints and route information
• Some units come with software to store waypoint data on your home computer, so you can collect more information than the unit can hold on its own
• Some units offer an expandable memory

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