Those of you who spend time outside probably realize that it's wise to carry a map and
compass with you, just in case you get turned around or need to navigate your way back home.
But, even more important than just carrying a map and compass is being able to use them
correctly, should the situation ever arise.
And, in order to navigate accurately using a map and compass you need to compensate for
magnetic declination.
To illustrate the concept of magnetic declination I'm using this grapefruit, which symbolizes
earth.
And this pin symbolizes the north pole and this pin symbolizes magnetic north.
That's the earth's magnetic field where your compass needle points to.
So your compass needle is pointing here towards magnetic north and the grid lines on your
map are oriented towards true north.
So if you use your map and compass and don't take into account magnetic declination you'll
actually end up over here when you were trying to get right here.
So that's why it's really important to compensate for this angular difference known as magnetic
declination.
And, in order to do that, I'm going to show you how to use your compass to get to where
you want to be.
So let's take a look.
First turn your compass over.
Second, find the small declination adjustment screw that usually looks something like this.
Third, insert the key that's usually connected to your compass' lanyard and insert it into
the adjustment screw.
Fourth, turn the key until the declination indicator is the correct number of degrees
east or west of zero.
After setting your declination correction you won't need to account for magnetic declination
again until you move to a new location with a new magnetic declination.
Pretty easy right?
That's why we highly recommend using a compass with adjustable declination for any serious
backcountry navigation.
It just simplifies the process and really reduces the likelihood of making an error
out in the backcountry.
Now that you know how to adjust magnetic declination on your compass, let's take a look at where
you can find the information that will inform you of the number of degrees East or West
that you need to adjust for.
Most maps will feature a magnetic declination diagram that looks something like this, and
it will be towards the bottom.
It features two diverging lines with an angle listed nearby.
The angle listed informs you of the degree difference between the magnetic north line
and the true north line and so you can see in this instance we need to adjust our compass
8 degrees.
And since the magnetic north line is on the right, we would adjust it 8 degrees east.
However, if this magnetic north line was on the left, we would adjust it eight degrees
west.
Before you rely completely on the magnetic declination diagram printed on your map, always
check the date that the map was printed or last updated.
Always check your local declination from a trusted source before you begin navigating.
Now you might be wondering, why do I need to have the most up to date information regarding
magnetic declination?
And it's actually because there are two factors that are constantly changing that affect the
magnetic declination.
The first is your location on earth.
and then the second is year-to-year fluctuations in earth's magnetic field.
So first let's take a look at why magnetic declination changes base on your location.
Here you can see I'm going to illustrate with a grapefruit and this is true north and this
is magnetic north.
So if you're right here on the earth, your compass needle is pulling you towards magnetic
north and the map is trying to guide you to true north.
So as you can see there's a pretty big disagreement, which is why you want to adjust your compass.
However, if you're right here on the earth, your compass needle is going to be pulling
you towards that magnetic north and that magnetic north and the true north are actually on the
same line.
So, in this case, you actually wouldn't need to adjust your compass at all.
But next year, the earth's magnetic field might be here, and suddenly there's a little
angular difference there again.
So each year the declination for an area changes so it's important to always check that local
source before you head out to an area to get the most up to date magnetic declination info.
Now you know how to navigate more accurately by compensating for magnetic declination on
a compass with adjustable declination functionality.
However, there is still a ton more to cover on this topic, and you can learn more by clicking
right here on this video.