Triangulation in Three Easy Steps
Step One: Identify Features or Landmarks in the Terrain
To triangulate successfully, you must be able to see features or landmarks in the terrain and to identify these on your map. For this reason, this technique is tricky to use in low visibility, but in all but a complete whiteout you should be able to single at least a few usable landmarks or features in the surrounding terrain.
Some more prominent or obvious features you could use include buildings, peaks, knolls, hillocks, boulders, saddles, gullies, bluffs, lakes, ponds, and outcrops. Subtler features include steep points on a slope (marked by tightly packed contour lines on your map), turns or bends in a trail, river, or road, ridgelines, and/or trees and vegetation.
Step Two: Prepare Your Map
Before taking bearings to any of the above landmarks or features, you first have to take care of a few logistical necessities with your map and compass.
First of all, make sure you have adjusted your compass correctly for the area’s magnetic declination.
Secondly, orient your map so it is facing true north. This is done by aligning the orienting lines on your map with the north (red) needle in your compass.
Step Three: Take Bearings to Each Landmark
To take bearings from landmarks or features in the terrain, hold your compass flat in front of you and point the direction of travel arrow at the landmark. Then turn the compass dial until the magnetic needle’s red end is in the orienting arrow’s column on the bevel or needle housing. In hiking parlance, this is often referred to as “putting red in the shed.”
Protip: When using triangulation to get a bearing on locations in a specific direction, the further you can hold the compass away from your body, the more accurate the bearing is going to be.
Hence, we highly recommend buying a compass with a foldable mirror that allows you to take a bearing with your arm almost at full stretch.
Next, place your compass on the map so that the orienting lines are parallel to the map’s north-south or latitudinal meridian lines and then move your compass, keeping the orienting lines aligned to the meridians, so the top corner of the baseplate is positioned over or on the landmark.
Now, take out your pencil and carefully draw a line along the edge of your compass from the feature. Then take a bearing on another location in the distance, and draw a line on your map and finally repeat the process with a third landmark. Once you have done so, your position will be identified by the point on your map where the three lines you have drawn with your pencil intersect.
If you’re in a pinch or a hurry, triangulation can also be done with only two features or landmarks, but for the most accurate results we’d always recommend using three bearings.
Triangulation With a Single Landmark
If you happen to be situated on a very obvious, prolonged landmark—a path, road, river, or ridge, for example—then it is possible to determine your position using only one other landmark or feature in the terrain around you.
In this case, simply repeat steps one through three above, this time using the single landmark. The point where the line taken from the bearing of this landmark passes through the landmark you are standing on will give you your location.