Wilderness Navigation #9 - Adjusting Declination on your Compass

Learn to adjust the declination on your compass. Trying to add or subtract your declination is needlessly confusing!

I highly recommend using a compass with adjustable declination, because it makes using a compass a LOT easier.
For a long time, compasses simply didn’t have adjustable declination.
But now, many compasses have it, including the Suunto M3, my favorite compass. This compass is about $35, and has a lot of great features, which we cover in lesson #1.

A lot of old school navigation books and Youtube videos will tell you to add or subtract your declination to get a true north bearing.
The math is pretty easy, but remembering it years from now when you are lost and stressed can be really hard.

The advantage of using a compass with adjustable declination is that you measure all bearings relative to true north, and therefore don't have to deal with any kind of confusing backcountry arithmetic.

Once your declination is correctly set for your local area, you can pretty much forget about it for years to come.
If you travel to a different area that has a different declination, adjusting your compass to the new area takes about 15 seconds.

Let's look at the Suunto M3, and see how to adjust the declination.

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For this demonstration, we have two Suunto M3 compasses. The older yellow compass is adjusted for declination, the newer one is not.

Right out of the box, your compass will look like this.
If we rotate the compass dial to north, notice that the red orienteering arrow, also known as the “shed” is exactly lined up with the small triangular “Read Bearing Here” mark.
This compass is not adjusted for declination.

Now let's look at our yellow compass, which is adjusted for our local declination here in Oregon of 16° east.
Notice if the compass dial is set to 0° or North, the red orienteering arrow, or the shed, is now pointing at 16 degrees, not at zero degrees.

Now, when the red end of the magnetic needle is lined up with the orienteering arrow, or as we cover in Lesson 2, "put red in the shed”,
I'm compensating for the 16° east declination, and the actual bearing is to true north.

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Say I want to adjust this newer compass to the local declination in Oregon of 16° east.

If I turn the compass over, you can see that there is a very tiny screw on the underside of the base plate.
Turning this screw moves the orienteering arrow, and this adjusts the declination.
This compass comes with a tiny screwdriver on the lanyard, and we use this to turn the screw.
If you don't have this little screwdriver, the tip of a small knifeblade works as well.

It can be helpful to have your compass on a sheet of white paper for this next step.

Looking at the back of the compass, we can see East declination here, West declination here, a series of small red lines showing the declination, and a thin black line that extends down from the orienteering arrow.

What we're going to do is move the thin black line on to the proper declination mark by turning the screw.

To adjust your compass to East declination, turn the adjusting screw clockwise, and only just a little.
On this compass, turning the screw about a half turn moves the declination a whole 10°.

When your compass is properly adjusted, in this case 16°, turn the compass back over, and rotate the dial to 0° or north.
Notice that the orienteering arrow is now pointed a little bit off to the right, or East, rather than exactly North the way it was before.

Now anytime when the red end of the needle and the “shed”, or orienteering arrow, are lined up, you've compensated for the declination and all bearings measure to true north. This is the modern and WAY less confusing way to use a compass.

Thanks for watching. Please visit our website at www.croc.org for more videos on wilderness navigation and orienteering.

Видео Wilderness Navigation #9 - Adjusting Declination on your Compass канала Columbia River Orienteering Club