How Does A Magnetic Compass Work And How To Use It

compass map

Did you know?

One of the most useful tools created by man is the compass, and if you ever find yourself lost in the middle of the woods it can be potentially life saving.

Since it is so useful, we might ask how a compass works.

compass mark

In this article, we are going to walk through all of the neat details of compasses so that you will know everything you need to.​

Compasses give us the opportunity to navigate any terrain with a high degree of accuracy.

They are quite simple instruments but the majority of people are unsure how to use them correctly.

Guess what?

After reading this article, you will be able to tell which of the following is true of compasses and also answer these questions:

  • True or False: Compasses interact with the magnetic field of the Earth.
  • True or False: You should always keep the north end of the needle opposite of the orienting arrow when keeping a heading. 
  • True or False: All compasses can only be used with a map. 
  • Question: What is a compass?
  • Question: How many degrees are on a compass? 
  • Question: Why does a compass point north?

If you can’t tell which of these statements are true or false no worries, we will cover it all and more. There is much to learn about using a tool that can be indispensable!

We will focus on magnetic orienting compasses, and while there are several variants of these compasses that are available we will focus on parts and methods to read a compass that are common to all types.

If you don't own a compass yet, have no fear. We reviewed the top compasses that you can get here.​

Disclosure:   Some of the links in this article are affiliate links, where I make a small commission at no extra cost to you.

What are the parts of a compass?

compass heading

Compasses can come in a variety of shapes and sizes. Some are even built into other tools which can be handy.

Accuracy and capability will vary on different ones though.​

Regardless of how ornate, expensive, or cheap the compass is they can all be broken down into several similar components that are found on all compasses.

We will focus on the most necessary compass parts that are needed to utilize any compass you might find yourself with.

Let's look at the breakdown:​

  • Housing: The housing is found on every magnetic compass and is the round portion that contains the compass needle. This compartment is usually liquid filled which helps reduce the friction and allows the needle to move more easily.
  • Magnetic needle: A very small magnet that sits on a near frictionless point and responds to the Earth’s magnetic field. The different poles of the needle are different colors with the northern pole most often colored red.
  • Rotating Dial: The dial is a movable disk that surrounds the housing. It is most often labeled with the cardinal directions and degrees that will allow you to get a bearing. This is also sometimes referred to as the bezel.
  • Orienting arrow: This arrow is most often found within the housing and also rotates with the dial and will be important when orienting a map and generating and keeping a bearing. When generating a compass bearing this arrow will point north.
  • Orienting lines: These lines are also found within the housing and rotate with the dial. These lines are critical when gaining a bearing while using a map and will line up with the grid lines.
  • Base plate: Usually a clear, plastic base that allows the user to see parts of the map beneath the compass. This can serve as a ruler and strait edge to measure distances on a map.
  • Direction of travel arrow: Large arrow on the base plate that will point towards the direction you want to travel.

How Does A Compass Work?

To fully understand how to use a compass it is crucial to understand how do compasses work.

A compass, in its simplest form, is a magnet that is allowed to swivel from a fixed point in the middle of the apparatus.

compass parts

Basic science tells us that a magnet is comprised of two poles and opposite ends of a magnet attract. This is the underlying principle of a compass.

A common question is which direction does a compass point and why.

The answer is if its working properly a compass always points to North. The magnet that a compass interacts with is the magnetic field of the Earth.

The “north” end of the magnetic needle will point towards the Earth’s “magnetic north”.

To keep confusion at a minimum we call it the magnetic north to coincide with the four cardinal directions that are used.

It’s also important to note that the Earth’s magnetic north is not actually at the North Pole, but somewhere in Canada and it actually moves slightly year to year.

Basics Of Reading A Compass

Before we go into more detail on how to use a compass along with a map we will look at how to read a compass. We will describe the steps taken to determine a general direction that you want to travel.

  • Hold the compass flat and level with the direction-of-travel arrow facing away from your body.
  • Remember, at this point, the red portion of the needle will be pointing towards the magnetic north.
  • Decide which direction you want to travel. If you need to head due west you turn the dial until the W lines up with the direction of the travel arrow.
  • Now, turn your entire body holding the compass level until the north end of the needle lies within the orienting arrow. You have now set a compass heading!
  • As long as the north end of the needle stays aligned with the orienting arrow and you walk along the line extending from the travel arrow you will be heading due west.
  • The same steps apply to any direction that you want to travel.

Using A Compass With A Map

compass map navigation

Compasses are most useful when they are paired with a map and having an idea of your location on said map.

Using a compass with a map has a few extra caveats than just understanding which direction you are facing.

Here we will look at orienting the map to the compass, understanding how to get a compass mark or bearing, and reading and maintaining a compass heading.

Here are the steps:​

  • You first must orient your position with a position on a map. Then make a mark of your destination. If you have no idea where you are look for specific landmarks around you. You can also triangulate your position on a map, but that is beyond the scope of this article.
  • Place the compass edge in a straight line from your current position to the destination making sure the direction of travel arrow is pointing towards the destination.
  • Now rotate the dial so the orienting arrow and lines match up with the grid lines running north and south on your map. Your orienting arrow should be pointing north on the map when aligning.
  • There are 360 degrees on the rotating dial. You now have a compass bearing that is a specific degree. You can use this bearing to have a more accurate direction. Even if you lose site of a specific landmark you want to travel to you have a very specific heading you can keep.
  • Standing with the compass you rotate until the north end of the needle is within the orienting arrow.
  • The direction of travel arrow is now pointing towards your destination!

For more advanced information on map reading, check out this resource.

Conclusion

A compass can provide you a lot of information and you should have a basic understanding of how to gather that information.

You might be thinking of why you would ever need a compass when GPS is available, but batteries fail and there are still positions on the Earth where connection to GPS satellites is dicey.

Instead of a GPS, sometimes a watch with a built in digital compass is a great idea. There are high quality watches these days that use digital sensors to measure the earth's magnetic field. They don't require much power and are included as part of the watch.​

A compass is reliable and has stood the test of time. Hopefully, this article has provided all that you need to know to have the basics of what a compass is and how to use it.

If you have any questions, let me hear them in the comments below.​

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