Which is better for navigation — compass or GPS?

Here's the most important thing you need to know about a compass: There's no point in having one if you don't know how to use it. Your compass should come with directions on how to use it. Read them.

Because the needle of a compass is magnetized, it will always point toward magnetic north. You can use a compass without a map, if you just need to go in a very general direction in a straight line. But when you're in the wilderness seeking out a specific destination, you'll need a little more direction than that.

Pairing your compass with your map will give you more accuracy. It'll also alert you to any areas you won't be able to cross straight through, such as a river or a canyon. A map gives you directions, and a compass enables you to follow them. It's best to utilize a topographic map when hiking and exploring.

If you know where you are on the map but you don't know how to get to your destination, use your compass to take a bearing. Your compass lets you assign a numerical direction -- a bearing -- to any direction in the full 360-degree circle around you. This is important because, with a bearing, you can travel toward a specific spot instead of just in a general direction. Here's how to set a bearing. Your compass has a rotating ring around it. You'll see the ring is divided in increments that add up to 360 degrees. Align your map and compass both North, and place your compass over your location on the map. Imagine or draw a straight line from the compass center to your destination. The travel line on your compass will show a bearing number. Following that exact bearing will take you to your exact target on the map.

Once you've set your bearing, you're on the right track to finding your way. But there's still another wrinkle. ­Magnetic north isn't the same as true north -- it's close, but no cigar. Magnetic north is always moving, and we call this margin of error declination. Declination is an angle that measures the difference between true north and magnetic north. The angle varies depending on where you are on the planet. This is why it's important to always use a current map when you're in unfamiliar territory, especially when you're trekking long distances. With short distances, the declination may only be 100 feet (30 meters) or so. But when you're trekking long distances, the margin of error could be several miles (or kilometers). Your map will tell you the declination. When you make your navigation calculations, you add or subtract that angle from the compass bearing numbers. Some compasses only require you to make that adjustment once for your entire trip -- check your compass instructions for more about setting the declination.

Again, learning to read a compass and topographical map requires preparation and skill. Read the instructions that came with your compass, check your library, outdoor gear store or search for a tutorial online. Try doing a practice run at home before you go out in unfamiliar backcountry.

If using a compass requires so much calculation and skill, would a GPS make things any easier? Find out on the next page.

Global Po­sitioning System (GPS) devices are a relatively new navigation invention, considering we've been using compasses and maps for hundreds of years. Used by the military for years, the government opened up GPS satellites for civilian use in the 1980s.

A network of 24 satellites orbits the Earth twice a day, transmitting signals back to earth. A GPS receiver locks onto signals from three or more satellites to determine your location, using a method called trilateration. Your receiver calculates the difference between the time a satellite sent a signal and the time your system received it. Using the information gathered from several signals, the receiver triangulates your exact position. It can even determine how fast you're going and how long it will take you to reach your destination. GPS receivers are extremely accurate, many within 50 feet (15 meters) [source: Garmin].

Many GPS devices come loaded with maps that work in conjunction with the information from the satellite signal. Depending on the particular GPS unit you purchase, your device could come with road maps, marine maps, topographic maps, trail maps or ski resort maps. Keep in mind there are different GPS units for road travel, cycling, running and fitness, boating, fishing, flying and hiking. If your unit isn't loaded with the maps you want, you can purchase and download specific maps to the device. Maps vary widely in price. You can find some maps (like maps of national parks) online for free, or you can purchase device-specific maps from the manufacturer for around $100.

You're probably familiar with using a GPS system in your car. Simply enter an address and the device will calculate a route there and a route home. Some systems will even take into account traffic and construction conditions. But how does a GPS steer you in the wilderness?

A GPS receiver provides you with your location, distance/directions, routes and tracking. Tracking means that the GPS unit will provide you with a breadcrumb trail, in case you need to retrace your steps. You'll likely need to initialize and configure your GPS device before you can use it. This means acquiring a signal from the satellites. If your signal is weak or the system can't find enough satellites, then you shouldn't rely on the device for directions. A clear sky with few obstacles between you and it is the best for a strong signal. This may be difficult if you're under heavy forest canopy.

Program your GPS device using coordinates from your map. Set waypoints along the way -- starting with where you parked your car and ending with your campsite. These waypoints will build your route. You can learn how to do this by reading the instruction manual that came with the device. Obviously, you'll also need to know how to read a map. Practice at home before taking your GPS device out into unfamiliar terrain. Your local outdoor supply store may offer helpful courses on how to use a GPS device, as well as basic navigational skills.

It's important to remember that a GPS unit doesn't replace a map and compass. A compass won't run out of batteries, and a map will never lose its signal. Think of your GPS unit as a companion to your compass and map. And remember, the unit is only as good as the map you use along with it. Experts agree the best maps to use are the USGS Topographic Maps, which are accurate and frequently updated. Your GPS unit should also have an electronic compass.

­But we still haven't answered the question: Which is the better navigational device -- compass or GPS?

In order to determine which is better -- compass or GPS -- we need to t­ake a good look ­at the pros and cons of each. First, let's check out the pros and cons of the compass.

Pros:

Cons:

Now, let's check out the pros and cons of GPS:

Pros:

Cons:

Final conclusion: A GPS unit may provide you with much more detailed navigational information than you could ever get with a compass. But because it relies on battery power and a clear signal, any trekker should always hike with a good old-fashioned compass and a map, as well.