How to Use a Compass

We’ve put together a video on basic compass skills. As usual, we’ve added a text version below.

Suppose you are located at the East Trailhead for Headquarters Trail. You want to go straight to Point Crawford. There are two ways you can determine the direction you have to walk.

The first is to measure the direction using a map square or protractor on the UTM grid and convert that to a magnetic direction. Make sure you have the UTM grid lines drawn on your map. Then draw a straight line from your location to your destination. Extend this line long enough to cross one of the UTM grid lines.

You want to find out the angle of this line you’ve drawn. Take a map square that has angular measurements around the edges and place it on the map with the center on your line. Then slide it to the nearest UTM grid line so you can make sure that north on the square lines up with north on the grid.

You can also do the same process with your map compass.

Then read the angular measurement. For us that is 202°. After we account for declination we know we need to hike at a bearing of 191°.

The other way to determine your direction of travel is use a map compass with the map oriented to magnetic north. First orient the north line on the compass with the center line on the compass base plate. Next, place the compass on the map with the center line on the base plate aligned with north south edge of the map. Then rotate the map (and compass with it) until the north seeking needle lines up with the north line (and the center line, and the grid line). Now the map is oriented toward magnetic north.

Next place the compass on your current location with the center line pointed toward Point Crawford. Then rotate just the ring on the compass to align the north line with the north seeking needle. Read the degree measurement at the center line to get 198°. No conversion is necessary because the map has been oriented towards magnetic north.

Notice that these two different techniques gave us two different numbers. Its important to understand that your map tools only have a certain precision and making these measurements by hand is going to create some errors.

It is important to be as careful as you can but also use your understanding of the terrain to help complete the navigational picture. How precise you are largely depends on what you are looking for. Is it one single tree where you stashed your buried treasure or a prominent hill top with great scenery?

Either way once you have your direction figured out, align that direction with the aiming lines on your compass. Then choose physical object between your compass and your destination and walk toward it.

Find more from our Navigation Skills series here.

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