A compass is a fundamental tool for the trail, and should be a part of every outdoor gear bag. But how exactly does it work? Fortunately, using a compass isn’t overly complicated, and when combined with some basic knowledge and a little practice, it becomes an easy and reliable tool for navigation.
Today you’ll learn the essential components of a compass, how to adjust it for declination specific to your region, how to take a bearing to a landmark, and how to follow a set bearing in your compass.
The Parts Of A Compass
Alright, first we start with the basics. Let’s explore the essential components of a compass, how to adjust it for declination specific to your region, how to take a bearing to a landmark, and how to follow a set bearing in your compass.
For starters, let’s familiarize ourselves with the various parts of the compass.
The largest part of the compass is called, the base plate. The base plate is usually transparent. This allows us to see and reference the map underneath.
At the front of the compass you’ll find an arrow. This is called the direction of travel arrow. It’s often at the end of a line, called the index line. You’ll use this to reference bearing numbers.
Along the side you’ll find rulers that aid in distance calculation.
The round part of your compass is called the compass housing, and along the outside edge, we have the bezel and compass dial, which rotates to set bearings in degrees.
Within the round housing we can see the red and white magnetic needle, the north-south lines, also called orienting lines, as well as a graphical arrow, called the orienting arrow.
You’ll hear many people refer to this graphical arrow as “the Shed” since it looks like a small shed. But more on that later.
Some compasses also feature a declination scale, this simplifies things when you adjust for the variation between true north and magnetic north, also called declination.
Declination Basics
Declination seems complex at first, but it’s a simple and important concept to understand. Declination is simply the angular difference between True North, (The direction that points directly towards the geographic North Pole), and Magnetic North, (The direction that a compass needle points to as it aligns with the Earth’s magnetic field).
Since the compass needle points to Magnetic North, and most maps are usually oriented toward true north, failing to adjust for this variance, or declination, can significantly impact navigation.
Keep in mind that the declination value varies East or West, depending on your location.
The Declination Diagram near the Legend on your map will provide you with the declination direction and degree for your location. For this reason, always make sure you have the latest version of the map for your area.
Different compass brands offer different methods for setting declination into the compass, so check with your compass manufacturer for the details.
Here in Arizona, we have around a 13-degree east declination. While 13 degrees out of 360 may seem minor, during long trips or in regions with more extreme declination, such as the far north, these seemingly small numbers can really add up, potentially leading to significant deviations from intended paths over long distances.
So with that in mind, here’s how to incorporate declination into your compass for accurate wilderness navigation.
Adjusting For Declination
First we’ll start by setting three six zero degrees to your index line.
Next, find the declination of your area, in this example, 13 degrees east. Turn your compass bezel to the east to adjust for 13 degrees of declination, from three six zero to three four seven.
To always know which way to rotate your compass bezel, remember the old adage, “East is least, west is best”. If your map says 13 degrees east, subtract 13 degrees from your north bearing of three six zero.
Lastly, hold the compass flat in your palm in front of your body and away from any metals. Rotate your body and the compass, and place the magnetic north red arrow inside the orienting arrow, or the “shed”. This process is also called putting “red in the shed”.
Adjusting for declination is an extra step, but doing so is an essential good habit that will ensure your readiness for situations where declination significantly impacts the journey.
Bearings
A bearing specifies a direction of travel represented as compass degrees, north being assigned three six zero, east – zero nine zero, south – one eight zero and west – two seven zero.
With this in mind let’s explore the 2 main ways to quickly orient yourself in the wilderness that don’t require a map.
Taking A Bearing To A Landmark
When you can see a landmark that you’d like to travel to you can easily learn what bearing you’ll need to take to get there.
Taking a bearing to a landmark is a simple two part process. First, choose your landmark and hold the compass flat in front of you at waist level. Point the direction of travel arrow directly toward the landmark.
Next, rotate the compass bezel dial to align the orienting arrow with the red end of the magnetic needle, also known as placing red in the shed.
Lastly, read the bearing where the front of the dial meets the index line and direction of travel arrow. You can now follow this bearing to reach your chosen landmark.
Following A Bearing
When you know which direction on the compass you’d like to travel you can easily input that bearing into your compass to help you get there. All you need to do is follow this two part process.
In this example, let’s say we knew we wanted to walk directly west, or two seven zero degrees.
First, rotate the compass dial until west, or two seven zero, lines up with the index line, or front of the compass.
Next, holding the compass flat in front of you at waist level, rotate your entire body and the compass base plate until red is in the shed, lining up the red magnetic needle with the red orienting arrow.
Now, you and your compass are both facing due west and you can walk out on that bearing to reach your destination.
Compass skills can seem overwhelming at first, so take what you’ve learned here, go outside, and try it out!
