Compass Navigation
Topic One: Walking A Line Of Bearing
By Blake Miller
Before technology entered the backcountry world of the outdoors, the primary and proven tools of navigation were a map and compass. Compass navigation remains an important component of the “Ten Essentials” for wilderness travel. Knowledge of how to use map and compass takes education and practice. Further, such knowledge will enhance GPS navigation as many concepts are interchangeable.
This article will discuss one of the basic uses of a compass, how to adjust the compass to walk a specific direction to get to a destination; to get from point A to point B.
Let’s start with a review of the key features and parts of a compass; see Figure 1 below. This figure is an example of a standard baseplate compass found in most outdoor stores. I recommend the backcountry navigator use a declination adjustable compass such as the Brunton 8010G or the Silva Ranger 515CL.
Figure 1
- The red magnetic needle rotates freely and points to magnetic north. Remember that metal objects such as belt buckles, watchbands, rifle barrels and car bodies will deflect the needle. Battery powered electronics will cause the needle to deflect too.
- The “direction of travel arrow” points in the direction of intended travel. Always point the direction of travel arrow away from you; perpendicular to your body.
- The “compass housing” rotates on the baseplate. The degree dial (0° to 360°) of the compass is found on the housing. With the baseplate, the “compass housing” can be used as a protractor while plotting on a map or adjusting to a specific direction.
- The “orienting arrow” is a red arrow inscribed in the compass housing cylinder. As the cylinder rotates so does the red arrow. The “orienting arrow” is not the red magnetic needle.
For more detailed information refer to the compass’ owner’s manual.
Let’s define some important terminology.
- Bearing: The direction to an object is the bearing. Bearing information is expressed in degrees such as 090° or 320.°
- Heading: The direction one is facing. If the hiker is facing north then the heading would be 000°. If one is going to travel to an object that has a bearing of 120° then the heading could be 120.°
Now that some of the key concepts of a compass have been discussed, the next series of steps will involve applying this information to a map:
- Using a map to first determine a start point and a destination.
- Laying out a track (the hiker’s path through the woods) on the map with a straight edge. Laying out a track gives the hiker the direction need to get to the destination.
- Determine the bearing from the start point to the destination.
- Adjusting the compass to travel a specific bearing to reach the destination.
For this exercise, the western shore of Sunset Lake will be the start point and the destination will be the eastern shore of Colt Lake; see the map in Figure 2.
Figure 2
A straight edge or ruler is used to layout a track from the start to the destination. (The general direction of travel is indicated by the red arrow.) The track is the desired path through the woods. Do you need to layout a track line, the answer is No. One could just “wing it” and estimate the bearing to Colt Lake. That said, in back country navigation, accuracy is important.
In Figure 3, the compass is placed on the map with the clear baseplate aligned along the black line (adjacent to and parallel to the black line.) The compass is placed so that the direction of travel arrow is pointing toward Colt Lake; pointing from start to finish.
Figure 3
In Figure 3, the compass housing (with the bearing information) is rotated so that north (the “N”) of the compass housing is aligned to map north; map north is straight up to the top of the map. In this example the map’s grid lines are used to align the compass housing; red compass lines (in the compass housing) become parallel to map black grid lines. Once adjusted, the compass direction provided is 018°.
At this point the traveler has learned that the direction from Sunset Lake to Colt Lake is 018°.
Note too that bearing information is expressed as three digits, 018° instead of 18°.
I in my formal navigation classes, I recommend to my students to double check one’s work. For example, move the compass out of the way and look at the black line drawn on the map. Does the line look as if it is laid out to the north east, does the bearing of 018° make sense?
Now it is time to move from the western shore of Sunset lake to the destination.
As shown in Figure 4, hold the compass at waist level. The base plate and direction of travel arrow should be perpendicular to the body.
Figure 4
With the compass adjusted to 018°, turn left or right and watch the red magnetic needle move. Continue turning until the red magnetic needle aligns directly on top of the red orienting arrow of the compass housing. With the two red components aligned the compass is now pointed in the direction of travel (018°.)
With the compass aligned and held as discussed above, the hiker should
· Use the direction of travel arrow essentially as a sighting tool; pointing in the desired bearing of 018°.
· Look down range (on the bearing of 018°) and sight on a distant object such as a single tree or land feature several hundred yards away.
· Using the feature as a landmark, walk straight to the object without using the compass. On arrival sight on another object, repeating the process until arrival at the destination. This process is akin to leapfrogging through the woods along the line of bearing to reach your destination. It also keeps you moving in a generally straight direction as you move forward.
· Note that in featureless terrain, a hiking partner can move downrange several hundred yards. To keep the partner on track, his position left or right of the line of bearing can be adjusted by hand signals or voice commands.
References that I frequently use are:
Staying Found, The Complete Map & Compass Handbook by June Fleming