If you’re like me, you have a smartphone.
- What is a Lensatic/Military Compass?
- Different Ways to Use
- How to Find Your Course Bearing AKA How to Shoot Azimuths
- How to Set a Course
- How to Follow a Course
- Tips & Tricks
I have half a dozen navigation apps on my phone, so I rarely get lost!
But phones have several major weaknesses: battery life and signal reception.
Both of those work against you when you’re tromping through the woods.
So, just when you need your phone’s navigation aids the most, they can let you down.
There’s a low-tech solution to this problem.
Though such a simple device has been around for about a thousand years, compasses have not lost their utility.
They don’t need electricity and they can handle almost any weather condition.
The first part of this article explains the basics of lensatic compasses and how to use them.
If you already know how to use one, feel free to skip ahead.
There’s some more advanced knowledge near the bottom!
What is a Lensatic/Military Compass?
At its most basic, a compass is a device which uses a magnetized needle to find magnetic north.
The earth has a magnetic field which pushes on magnetized needles.
Maps are typically made so north is up.
You can, therefore, use a compass to figure out your bearings and know which direction is north.
Once you have that, you can use a map to determine where you need to go.
A lensatic compass, also called a military compass, is a more advanced and useful version of a magnetic compass.
The term “lensatic” refers to the magnifying lens that helps you use the compass more effectively.
They’re also called military compasses because this is the design used by the US Military.
Lensatic Compass Parts
There are multiple parts to a lensatic compass.
The biggest part is the base, the compass itself.
There will be a floating needle and a bunch of information around the outside of the dial.
Those are the 360 degrees you’ll use to figure out directions.
There’s also a movable bezel with a mark painted on it or etched into it.
The other parts fold away from the compass.
The cover protects the compass from damage and also contains a wire stretched from top to bottom.
That’s the sighting line.
The other piece that folds away is the lens bracket.
It holds the lens.
Lastly, there’s a curved wire thumb loop.
You can put your thumb through it for greater stability while using the compass.
Now that we know what a lensatic compass is, let’s find out how to use one.
Different Ways to Use
There are different ways of holding the compass.
It’s worth experimenting with them to see which one is best for you.
Compass to Cheek
The most precise method of using a compass, this method is similar to using a handgun.
Unfold the compass so the cover is at a 90-degree angle and the lens is at a 30-degree angle.
Place your thumb through the thumb loop, hold your index finger alongside the body of the compass, and support it with the rest of your fingers.
Take your other hand and grasp the hand that’s holding onto the compass.
Much like holding a pistol, this increases the stability of the compass.
Now, bring the compass close to your eye, so the thumb loop is touching your cheek.
Make sure you’re holding the compass level!
Look through the lens and align it and a distant object with the sighting wire.
You’ll look through the lens and read the numbers.
Now you can shoot the azimuth and figure out the direction of that object.
Also called the center hold, this method is a little less accurate but is easier to perform.
Start by putting your thumb through the thumb loop and putting your index finger alongside the compass, similar to the cheek method.
Put the thumb of your other hand on the compass, between the compass body and the lens.
Extend your other index finger alongside the compass body and wrap the fingers of that hand around the fingers of your first hand.
Now, hold your elbows tight against your sides.
Point the compass in a direction by moving your entire body.
When aimed where it needs to be aimed, read the compass.
Since military compasses often glow, you can use this method at night.
You don’t always have to use two hands.
Using one hand is easier but is less accurate, because you don’t have multiple points of contact holding everything steady.
Stick your thumb through the thumb loop and rest the compass on top of your bent index finger.
You can either put it to your eye or hold it in front of you, depending on what you need to do.
Compass on Map
Another useful method is to orient your map to north by using your compass.
Unfold the compass entirely, so the sighting wire is level with the map.
Put the map on a level surface such as the ground, and place the compass on top.
Make sure that the sighting wire of the compass is perfectly parallel to any north/south lines on the map.
Rotate the map and compass together until the needle and the map both point directly north.
How to Find Your Course Bearing AKA How to Shoot Azimuths
The main use for lensatic compasses, other than orienting maps, is to figure out your bearing.
That’s the direction you need to take in order to reach your destination.
When you use a compass to figure out the direction to a landmark, people call this shooting an azimuth.
An azimuth is a measurement of how many degrees away from magnetic north your destination lies.
So, to shoot the azimuth, hold the compass.
Aim it at a landmark.
Then record how many degrees that landmark is from north.
How to Set a Course
Now that the azimuth has been shot, let’s use that information to set your course.
Lensatic compasses have a bezel that rotates around the dial of the compass.
On that bezel is a mark.
When you shoot the azimuth, rotate that bezel so the mark lies directly in line with north.
Set up correctly, when the bezel mark and needle are aligned, the sighting wire points at the chosen landmark.
How to Follow a Course
Now that we have a destination set and know the direction we need to take to get there, let’s follow the course!
The reason you want to set up the compass rather than just keep your eyes on the landmark is because your vision may become obscured.
But, so long as the bezel and needle line up, the sighting wire will point at that landmark.
Keep heading in that direction and you’ll eventually reach your target.
It’s a good idea to stop every now and then to take your bearings again.
Even if it’s at the same landmark.
It’s easy to get off track when the terrain is uneven, so this will help keep you on the right course.
Tips & Tricks
While we’ve already covered the basics on using a lensatic compass, the following information will improve the accuracy of your bearings.
Like any skill, it is good to practice navigating with a lensatic compass before your life depends on it.
If you’re figuring out how to use the darn thing when you’re lost, you likely won’t get it right.
So try it out in a safe place.
For example, navigate your way across a city park.
You can even practice in a large parking lot.
The important thing is to practice!
One of the difficulties inherent to using a compass is that magnetic north is not the same as true north.
In fact, it even slowly wanders around!
You’ll need to look up the magnetic declination of your area.
It’ll be a few degrees.
Not much, but enough to push you off-course.
Once you know your local magnetic declination, you can factor it into your compass reading.
Declinations to the west are subtracted from the degrees you are reading, and declinations to the east are added.
North is 0 degrees, so a declination of 10 degrees west would mean that you would point at 350 degrees to point at true north.
Some compasses can be adjusted to include declination, so after adjustment, a reading of 0 degrees would point at true north.
Others can’t be adjusted.
A piece of tape is useful in this case.
Just use the tape to mark the angle you need to point the needle in order to be pointing at true north.
Sometimes, you’ll encounter an obstacle you’ll have to walk around.
These can knock you off your path because, if you don’t move around them a perfect 180 degrees, your bearing will be incorrect on the other side.
There are several ways to combat this problem.
The first is to alternate the direction you take when detouring around obstacles.
Go around the first obstacle to the right, the second to the left, etc.
The second method is to travel at right angles.
When you hit the obstacle, change your azimuth by 90 degrees, say, to the right.
Then travel for a specific distance sideways to the original azimuth.
Turn your azimuth back to the original direction and move until you’re past the obstacle.
Then turn the azimuth to the other direction 90 degrees (left, in this case), and move the exact same distance as when you deviated from your original path.
After you’ve reached your original azimuth line, turn the bezel to match the original azimuth.
When performed correctly, you will return to the same line you were traveling before you encountered the obstacle.
Of course, if it’s at all possible, the safest thing to do is to shoot an azimuth on the other side of the obstacle.
This will ensure you’re traveling in the correct direction.
Here’s a video that can help:
The landmark you choose can be anything visibly noteworthy.
Towers, hills, mountains, and particularly tall trees are all a good idea.
It’s even better when the landmark is something marked on your map.
Then you can use a series of landmarks to plot the path to your destination.
Avoid Magnetic Fields
This may seem obvious, but it trips up a lot of people.
Magnetic fields will cause your compass to point in the wrong direction.
They call this “magnetic deviation.”
Almost any electrical item can produce a magnetic field.
So keep radios and phones away from your compass while you’re using it!
Large chunks of metal can also sometimes affect the magnetic field around your compass.
A truck, your radio, or even the barrel of your hunting air gun can push the needle away from north.
According to the military, a rifle can interfere with a compass from a distance of half a meter.
Power lines? Fifty meters.
Even if you’re naked in the wild, iron deposits can mess you up.
There’s a lot of iron in the earth’s crust, so be careful around areas known for iron.
You can often recognize iron deposits by how the rock looks red or rusty.
Yup, even iron ore rusts.
Using a compass is not as easy as downloading an app to your phone.
But a compass can never lose connection to the GPS satellites and will never run out of batteries.
Using a lensatic compass to navigate is an important skill to learn.
It may take a while to get it, and you should practice in a safe location before relying on one, but few devices are more able to help you navigate your way to safety.
Unless you are stranded on a deserted island, knowing how to use a compass just may save your life!