Using your Compass with a Map - Measuring Angles with your Compass
When we use our compass to “sight a bearing”, we are measuring the angle between Magnetic North, our location, and a distant object.
Hold the compass with both hands. Position the compass in front of your body at a comfortable arms length and at about eye level.
Hold the compass level. The compass should be level from side to side. This is easy to see.
You also need to hold the compass level front to back. With the sighting notch at eye level, the base plate will be just below eye level and you should be able to see just a bit of the top of the baseplate. If you see a lot of the bottom or top of the baseplate, your compass is not level.
Finally you need to line up your eye, the needle pivot point and the sighting notch. Use your wrist to rotate the compass on the vertical axis, until the black line in the mirror, is aligned with the pivot point of the needle.
The base of the compass should now be level, and the magnetic needle should be free to move. Adjust the flip up mirror so that the magnetic needle and the orienting arrow is visible. The mirror will be about 45° from the base plate of the compass.
Now that we have the compass level, the magnetic needle will align itself with the Earth’s magnetic field, pointing towards the Magnetic North Pole.
We’re ready to point the compass at the distant object. Turn your entire body, holding the compass in your hands, until the distant object you are sighting is aligned with the sighting mechanism on your compass. Let’s look at that from eye level.
Next, look in the mirror and turn the dial of the compass until the magnetic needle is parallel to the edges of the orienting arrow on the base of the capsule. Depending on your viewing angle the needle may not appear to be centered in the orienting arrow. This is not a problem as long as the needle is parallel to the edges of the arrow. Again lets look at that from eye level.
Recheck that your compass is still aligned with the distant object. It is usually necessary to make several fine adjustments of the compass position and dial rotation before you will be satisfied that you have everything adjusted correctly.
You can relax your stance, open the mirror, and hold the compass at a comfortable distance to read the bearing at the index line.
When you write the bearing down, follow it with the letter “M” or the abbreviation “Mag.” to indicate that the angle was measured using Magnetic North as the 0° reference. When you relay the bearing verbally, make sure you say the word “magnetic” following the angle. In our example we would say, “62 degrees magnetic.”
Some compasses can be adjusted to read bearings relative to the other north references. Information on how to adjust your compass and when you might want to do this, can be found in the Understanding North References video in this series.