Never Get Lost

GPS Unit

GPS units have revolutionized backcountry travel. Owning one doesn't mean you should throw away your map and compass - quite the contrary - but one of these tiny units, no larger than a cell phone, can do amazing things.

Here's how a GPS works: Satellites launched by the United States military rotate in fixed positions in relation to the earth. Your GPS unit picks up signals from these satellites and, by analyzing where these signals cross, determines your position.

When your unit locks on three satellite signals, its accuracy is good. When it finds more than three signals, its accuracy is uncanny. (Note: The military has removed the built-in error once imposed for security purposes.)

A GPS unit costing a little more than $100 can: 1) tell your exact location either in latitude/longitude or in the Universal Transverse Mercator grid, the coordinate system used on U.S. Geological Survey map;. 2) point to north (as long as you're moving); 3) act as an odometer, telling distance traveled, speed, average speed, etc.; 4) point the direction to waypoints you've entered earlier; 5) show the route pattern you've traveled; 6) tell you time of day, the elevation, and the times of sunrise and sunset.

Spend a little more, and you can get a built-in magnetic compass, as well as map programs that allow you to view map segments on the unit's screen. When you get home, you can interface a GPS with your computer to view your exact route of travel superimposed on a map. Or, you can enter waypoints in advance of your ride and let the GPS guide you to them.

A GPS unit is best used as a supplement to the map and compass, not as a replacement for them. A good topo map is still necessary to see the big picture and to enter the information your GPS gives you. And don't discard your compass, because a GPS unit does have limitations. The biggest limitation is battery dependence, so always carry spares.

Also, your GPS unit must be able to have direct lines of sight to the necessary number of satellites to pinpoint your location. Obstructing this line of sight on trail might be a deep canyon, extremely heavy tree cover, or a blinding snowstorm.

These limitations noted, a GPS unit is a bonanza for the backcountry horse-person. Enter any trailhead as a waypoint before you mount up, then clear the odometer and put the unit in your shirt pocket. At a glance, you can tell how far you've traveled and at what average speed. Touch another button and an arrow appears, pointing back toward the trailhead. Should you come to an interesting landmark you haven't noted on the map, enter it as a waypoint. At home, you can pull out the map and, using GPS coordinates, figure out just where the landmark was located.

The GPS' capabilities do come with a certain price in time and effort. Although the units are extremely user-friendly, some learning is involved. However, mastering yours will be no more difficult than learning a new word-processing or photo-editing program. You'll find it whets your appetite for this whole business of land navigation. You'll never be content again leaving knowledge of your position on the map to another.

Dan Aadland (http://my.montana.net/draa) raises mountain bred Tennessee Walking Horses and gaited mules on his ranch in Montana. His most recent books are The Best of All Seasons, The Complete Trail Horse, and 101 Trail Riding Tips. Sketches from the Ranch: A Montana Memoir is now available in a new Bison Books edition.