How to use a compass
- the way I use the compass to get around -

I did not intend this section to be a good (or complete) manual on how to use a compass. It is just to give you an impression of what you can do with one. When you buy a compass, make sure that the manual that comes with it contains a section that explains the stuff I mention in a understandable way.

How does a compass work?

The earth has a magnetic field. A compass has a magnetic needle. This needle reacts to the magnetic field of the earth. When this needle can move freely, the red part will turn to the north and the white part will turn to the south.

This method is not 100% accurate. The magnetic field of the earth can be rotated a bit on some places. Also external magnetic fields (such as electrical wiring inside a car) or magnetic metals (such as steel & iron of your car or a bridge) may influence the needle. To get a rough indication, the compass will however work well enough.

What type of compass?

When you start looking for a compass, you will find a number of types. The most simple ones you can find in car-shops. They are just a stick on gadget that show the direction you are driving. These are worthless. You need to stick them to your dashboard (and I bet they will fall off after some sunshine). For a compass it is required that the magnetic needle (or ball that is used in such compasses) can move freely. The liquid inside these kind of compasses already generates a to big friction. Another thing is that you will need to mount it on the dashboard. That happens to be the place where most electrical wiring is... You also can not use it in the way I am going to describe below.

When you go to an outdoor shop, they usually offer different types of compasses. Those should come with a manual. That was also how I did find out how they work. They start simple, just a needle without anything else. Then they get more-and-more complex with mirrors and lenses. The mirrors can be used to get a heading. I will get to that later, but you will not need that unless you also plan to use it for hiking.

The type you need for driving around is almost the simpelest one. A base plate that holds an arrow in the middle. It should have a rotatable dial with some lines in it and a section with some wider bars. I will explain how to use these features later in this section.


This type will do: A base plate with an arrow in the middle. The needle should be in a dial that you can rotate. The dial should have some lines and some bars. In case you need it for hiking you are better off with a compass equipped with a mirror (they are more expensive)

When you are going to hike, you might like to take headings. This means that you get the direction of a recognisable object. This can be a bridge, a church-tower, a castle, a hilltop and so on. To take a heading, you turn the compass in the direction of the object. Some holes help you to do this. Then you turn the dial to align with the needle. This is where the mirror helps you. After that you can read from the compass in which heading the object is from your position. When you can take two headings, you can define your location (when you have a map). While driving around in a car in a developed country, you will get to a signpost within a few minutes. You can also check which direction the road that you are driving follows. When you like you can then check your map to see which road you are on. You won't need to take headings to do this. So you won't need all those gadgets...

A quick check to see which direction you're going

Once you have mounted the compass as I will tell later, you can have a look on it to see which direction your are driving. The red part of the needle will point to the north. The white part will point to the south. Knowing this you can roughly see where you are going. When you do not have a compass and the sun is shining you can use this. At 12:00 it will roughly be in the south. In the morning it will be in the east and late in the afternoon it will be in the west.

When you are travelling you usually know which way you are going. If you took a wrong turn somewhere, or you left a parking and went in the wrong direction, you will notice this immediatly.


In this case you are driving towards the east. You do not need to use the dial or the baseplate for this.

Using dial & map to verify the correct direction

This is the part that becomes a bit more complex. But once you know how to do this, a compass won't hold that much mysteries anymore.

The first thing you need to do is set up the dial on the compass. To do this, you take your map (with the north away from you, this will be fine on most maps when you can read the text). Once you have this, you will place the compass on your map. The arrow should be on top of the road that you plan to be on. It should also point in the driving direction. Where the dial is does not matter. Place it anywhere you like, as long as it is not in your way.


The arrow of the baseplate is on top of the road that you like to follow. It also points in the correct direction. In this case I like to drive to the left-bottom of the map. That is a south-east direction.

The next thing you need to do is to set the dial. Align the dial in such a way (without moving the compass) that the lines inside the dial are parallel to the vertical (north-south) gridlines of your map. The red bars should be pointing to the top (north).


This image shows the dial in detail. The previous image shows the dial & compass on the map as it should be when you're finished.

Notice that you do not need to care about the needle when setting up your compass. When you use the compass in combination with your map, you do not use the needle. The red bars in the dial are used instead.

Once you have set-up the dial, you can place the compass in the 'holder'. You can then verify that you are on the correct road by checking if the red part of the needle is between the bars. A slight difference is no problem. If the white part is between the two bars, you are probably on the right road, but travelling in the wrong direction.


When the red part of the needle is between the 'north'-bars, you are going into the correct direction. Usually this means that you are on the same road as you planned to be.

Using wheel & map & signpost to find current location

Even when you do everything right, you can get to a point that you are 'lost' (men will never say they are lost, they always perfectly know where they are...). In that case you can drive to a junction where there is a signpost. Point your car (or just the compass) in the direction of the road that you are on. Then rotate the dial in such a way that the red part of the needle is between the two bars.

Then get your map and find the place(s) mentioned on the signpost. You can then check the junctions that you might be on by placing the compass on your map. Don't rotate the dial and make sure that the bars are pointing to the top (north) of the map. The road you are on should be parallel with the arrow on the baseplate.

In fact you do the same as I wrote above. Instead of using the map to set te dial, you now use the magnetic north.

Mounting the compass.

This can be a tricky thing and it will need some experimenting. The compass should be placed at a location where it is not influenced by the iron of the car. You can notice this when the needle rotates when you move the compass. Usually a distance of about 50cm away from the iron parts will do. The car is not a perfect cage of Faraday so the compass will work inside.

The place should also be away from electrical wires. A car uses direct current. This generates a magnetic field that interferes with the earth's magnetic field. You can easily check this by swithing on/off the ignition and other circuits using your key. Keep an eye on your compass while switching on electrical devices (such as lights or windscreen-wipers). They might influence the compass. In that case try other places inside the car.

Once you have found a good spot, make some kind of holder that keeps the compass horizontal (the needle must be able to move freely, when the compass is tilted to much this will no longer be possible). When the compass is inside the holder, the arrow on the baseplate should point to the front of the car (parallel with the side of the car of course). The holder should be constructed in such a way that you can also get the compass out again. After all you will need to set it up using your map.


Last year I did make a 'temporary' holder using some tape and a chewing gum package. But until now I still use it... It is on plastic engine cover. Starting the engine turns the needle around. But for the rest this is a perfect spot.

Using a compass to hold your map in the correct way

When you are holding a map, it can sometimes still be confusing to find some places. If you happen to have a compass, you can put this on top of your map. Then you can rotate you map in such a way that the north of the map and the north of your compass are aligned. When you do this the real world and the map have at least the same orientation.