Map Navigation 101: Bearings

A month or so ago we offered the first in this series of posts on Map Navigation.  That post addressed declination by providing some background information then presenting a video tutorial presented by Sierra Designs and Andrew Skurka.  They have now produced another video that discusses bearings and how to find a bearing in the field, how to find a bearing on a map and how to transfer a bearing from map to field.

What is a Bearing?

A bearing is simply the horizontal direction from one point to another.  Sometimes bearings are expressed in terms like northwest and southeast or even north-northwest.  For example,  “that mountain is west of here.”  For more precision,  bearings are usually presented in degrees with north at zero degrees and south, being a half-circle away, at 180 degrees.  West, for example, is then 270 degrees.  When using degrees, one might say “the bearing to that mountain is 270 degrees from here.”  When something isn’t exactly west or northwest, we can use degrees to be more specific like, 275 degrees from here.  Conveniently enough, good compasses have these degrees marked on them.

When is Knowing a Bearing Helpful?

Let’s say you are in a forest opening, can see a mountain in the distance and you want to go to it.  You can determine the bearing to the mountain with your compass.  Once your compass is set properly,  you can use it to follow a line to the mountain.  That’s particularly handy when you get into the woods and can no longer see the mountain.

Now,  suppose you are leaving a trail and you know where you are.  You want to travel to a particular place, but you can’t see it.  You won’t be able to determine the bearing to your destination like we did with a mountain we could see.  Instead, we can determine the bearing from where we are to where we want to go on the map.  Given that bearing, we can set our compass and head off into the wilderness directly toward our destination.

How to Find a Bearing

Here are the steps to find the bearing to the mountain that we can see on the horizon:

1. Hold your compass in the palm of your hand with the direction of travel pointed away from you
2. Turn your entire body until the direction of travel arrow is pointed at the mountain
3. Turn the dial on your compass until the north arrow is pointing to north on the compass dial
4. Read the degree number that aligns with the direction of travel arrow.

Now,  you can keep the north arrow aligned with north on the compass by moving your body – NOT by moving the dial – while walking where the direction of travel arrow points.  You will want to follow the compass carefully and recheck your bearing when, or if,  you can see your destination along the way.

You may be given a bearing from a known point, perhaps by getting it from a map.  To follow the example in the video, let’s  say the bearing is 200 degrees. Here are the steps to setting that bearing on your compass:

1. Hold your compass in the palm of your hand with the direction of travel pointed away from you (same as above)
2. Rotate your compass dial until 200 degrees lines up with your direction of travel arrow
3. Rotate your whole body until the north arrow is pointing to north on the compass dial

That’s it.  The direction of travel arrow is now pointing along that bearing.  Compare the two sets of steps and you will see that they are different, but logically consistent.  In both cases you want to get the bearing degrees aligned with your direction of travel and you want north on your compass pointing north.  Just remember, if you can see the point you want to reach, point the direction of travel arrow at it THEN get the compass needle pointing at north on the dial.  If you already know the bearing, rotate the dial so it is at the direction of travel arrow THEN get the compass needle pointing at north on the dial.   You only rotate the dial once and your body once regardless of which way you are setting your bearing.

Getting a Bearing From a Map

Remember the protractor you used to draw angles on paper?  Typically they are only a half-circle so they displayed only 180 degrees.  While our compass has 360 degrees, it can be used the same way as the protractor.  When working with the map, it doesn’t matter which way we are pointing it, north is always toward the top.  If we have two points on the map, we just want to determine it’s angle from north – in a clockwise direction.

Here are the steps to finding the bearing of the line between those two points:

1. Draw a line on the map connecting the two points using your compass a straight edge
2. While holding the compass edge against the line, rotate the dial until north on the dial is pointing north on the map.
3. Read the bearing at the direction of travel arrow.

Now, suppose you are traveling along a path described in terms of points and bearings.  You are at point A and are told to travel on a bearing of 225 degrees from there.  You want to know what the terrain will be like and what you might find along the way,  so you want to mark that bearing on your map so you can study the situation.   Here’s how:

1. Set 225 degrees on the dial to match the direction of travel arrow
2. Put the edge of your compass on point A
3. Rotate the entire compass, while keeping point A on its edge, until north on the dial points to north on the map.
4. Draw a line from point A along the edge of your compass to see where that bearing will take you.

Again the steps are different, but logically consistent. In the first case, you know the line and want its bearing.  In the second case you know the bearing and want to draw the line.

Practice

While these instructions are pretty simple, it takes some practice for them to be come second nature.  To get a better idea of how bearing work watch the video, then take your map and compass outdoors and try all the different ways to find and transfer bearings.

The Video

 

Please Share