Identify Terrain Features
Constantly check your map position as you hike. When you find a good vantage point, match key landmarks.
Circular contours usually indicate high points. They may encompass many miles (ranges) or small areas (summits). Also, look for an “X” or precise elevation marking prominent peaks. Use features like secondary summits, passes, or water features to confirm your position.
Ridges and Valleys
U- and V-shaped lines indicate ridges, valleys, or drainages (V’s indicate sharper relief and U’s mean mellower terrain). In valleys, streams may run through the contour lines’ curves, which point uphill. Along ridges, the tips of the Vs point downhill; streams (if present) may run to the side.
Contour lines represent elevation change, so the closer they are, the steeper the terrain. Tightly packed lines indicate cliffs; examine them carefully when planning off-trail travel, as they often cut across consistent aspects or elevations. Beware: Short-but-impassable walls can fall between contours.
WARNING! Avoid Common Mistakes
Remedy navigation traps caused by inexperience and overconfidence.
>> Beginner: Over- or underestimating a map’s scale can lead you to misinterpret terrain.
Fix: Practice using maps of different scales in familiar territory (try 7.5- and 15-minute USGS quads). Guess the time it’ll take to travel between junctions or landmarks, and note your travel time. If your estimate is within a few minutes, your skills are getting sharp.
>> Intermediate: Bending the map. That’s what happens when what you expect to see causes you to misread terrain features.
Fix: Identify five distinct landforms in your field of vision before referring to your map. Match all five to your topo before proceeding.
>> Advanced: Lackadaisical map checking.
Fix: Scan landmarks in front of, around, and behind you. Match them to your topo every 15 to 20 minutes. Keep your map in an easy-access pocket (or in your hand) to remind yourself to check it regularly.
TIP: Follow Your Progress
Use your map to create a mental highlight reel of your route, and note the time you expect to hit key landmarks like rivers and passes. If you’re off-pace, stop, determine your location, and adjust your day’s plan accordingly.
Make Your GPS Talk to Your Topo
Use satellite data to find your location on a map.
>> Match map data and your GPS display
Inconsistencies between navigation tools can put you miles off target. Before translating GPS data onto paper, identify your map’s data sets, then program your receiver’s settings to correspond:
Map datum describes the survey grid used to create the map. Look for the citation in the margin, then update your GPS unit’s datum on the main settings menu. The most common North American datum are WGS 84 and NAD 27.
Most wilderness navigators use the UTM (Universal Transverse Mercator) reference grid, which is also BACKPACKER’s standard. Another common choice is the latitude/longitude grid. Maps usually have references to both.
Switch your receiver to true north mode if you’re working with a map only. If you’re using a compass, too, consider toggling between true and magnetic readings to smooth declination calculations.
>> Mark a waypoint and note your coordinates
Your GPS unit’s waypoint screen, which displays after you create a new point, shows a precise location as a coordinate set. To translate a pair of UTM coordinates from your GPS to your map, note the last seven digits of both the easting (listed first) and northing (listed second).
>> Find your position
Identify your map’s UTM grid, drawn in blue (older maps may have only tick marks on the margin). Match the first four digits of the easting and northing with the grid. The corresponding 1-by-1-km square marks your general location. Use the last three digits of each coordinate, which represent meters, to pinpoint your position within the 1,000-meter square. Measure east (easting) and north (northing) from the square’s bottom left corner; your position is where the measurements intersect.
Take Bearings and Triangulate
Use a map, compass, and nearby landmarks to orient yourself.
1. Orient the map. Align your map’s north-orienting arrow with the compass baseplate’s direction-of-travel pointer. Place the plate’s edge parallel to the magnetic north line (in the margin). Rotate map and compass together until the needle is ‘boxed’ by the baseplate.
2. Take a bearing. Hold the compass at waist height and point the direction-of-travel arrow at a known land feature. Rotate the bezel until the north-seeking arrow is boxed. Your bearing is the number on the bezel that lines up with your direction-of-travel arrow.
3. Transfer bearing to map. Keeping the north-seeking arrow boxed, place your compass on the map with the baseplate’s edge running through the center of the landmark; mark that line on your map in pencl.
4. Triangulate a position. Take at least three bearings using distinct landmarks. The point where they intersect (it may be a small triangle) is your location.
Skill: Triangulate with two lines.
If you are traveling along a known linear feature—like a river, mapped trail, ridgeline, or road—you can skip a step when triangulating your location. Shoot two bearings, translate them to your map, and use the known feature as your third point of reference. Your location is where the two bearings intersect the linear feature.
Adjust for Declination
Navigate accurately over distances.
Maps are oriented to true north, but compasses point to magnetic north. The discrepancy is called magnetic declination, and the farther east or west you get from the 0-degree line, the greater the impact on navigation. If you don’t correct for it (many hikers don’t), a 10-degree offset, like the one affecting parts of Colorado and Pennsylvania, could equate to a 1.7-mile error over 10 miles of off-trail hiking. Calculate your area’s declination with NOAA’s National Geophysical Data Center (ngdc.noaa.gov), or by referencing your map’s declination diagram (in the margin). Then correct for it:
>> Automatic Set your compass’s adjustable declination and program your GPS to display true north bearings.
>> Manual Shoot bearings with a non-adjusted compass. Add (for east) or subtract (for west) your area’s declination before translating the bearings to a map. Click here to learn more.