Navigation: Using your Compass
Guest Author: Carlos Daniel Cortesi
This is my favorite piece of survival gear. A well-made compass is rugged, simple, effective and easy to use. A compass has but one mission:
It’s that simple! If you know where North is, you know where the other cardinal directions are. If you know what direction you came from or what direction you are going you can easily return or arrive to your destination.
How it Works:
The convection currents of earth’s magma under the surface result in the planet's magnetic fields. Just like a bar magnet the planet has a North and South Pole. A compass is a small magnet suspended held friction less on a pivot point in a container which aligns itself with earth’s magnetic north.
I say magnetic north because that is not the same as true north. True (geographic north) is at the top of the earth (Latitude 90 degrees North) as shown on every map. Yet magnetic north is where the compass actually points due to its higher gravitational pull. This point shifts slightly from every year. The difference between true and magnetic course is called magnetic declination, and it varies depending on where you are. This is important when planning long treks with precise map calculations, yet for the weekend adventurer following established trails or short distances it can be overlooked. We will go over magnetic declination more in “Navigation Part 2”.
Remember the degrees from geometry class in high school? That is what compass reading is! Instead of the 0 degree line being horizontal, it is vertical, marking North. East is 90 degree right of North. South is 180 degrees, West is 270 degrees and north is back at 360 degrees or 0 degrees.
Imagine yourself standing in the center of the circle of degrees. All 360 degrees mark all the possible directions you can walk to. Remember that a compass always points 360/0 degrees, or North. No matter which way you turn or face the compass, the needle will always point North.
Using the Compass
Refer to the map above. Imagine you are standing on the red star, somewhere in Saudi Arabia. Assuming you can walk through continents and swim through oceans, what compass direction will you need to head in order to reach the green marker?
Notice the red arrow at the top right corner of the map. That shows you what direction is north. First thing one needs to do is orient the map north by pointing the map's north arrow in the same direction as the compass, now face north along with your compass before determining direction. You, your compass and map are now all facing north. Now we can measure degrees.
The green market is to our right, so East about 60 degrees.
The orange marker is just to the left of directly in front of us, placing it about 340 degrees and so on with the remaining two markers. This is how you can use a compass to walk to any direction on earth.
Putting it to Action
You are once again standing on the red star and we want to head to the purple market. We've guesstimated that the purple marker is about at a heading of 235 degrees. This is how you "set" that value on your compass and follow it until you arrive:
1. Open your compass and deploy it in front of you parallel to the ground (away from metal objects or power lines). Put your thumb through the thumb loop and support the compass with your fingers.
2. Notice how it immediately points north no matter which way you move.
3. Use the degree values! Compasses can come in both degrees and mils. This one has the inside numbers in degrees and colored red. They are easy to identify since degrees always run from 0 to 360, while mils go from 0 to 64 (measured in thousands) and marked in black.
4. Notice the black circle around the face of the compass. It's a rotatory dial design to "set" a compass heading; in our case it will be 235 degrees. The dial has a phosphorescent market (highlighted with a red box) which can be set to any number. With the compass steadily pointing north, we rotate the dial until the market is on top of our target number (235 degrees).
5. Instead of facing North, we will now face the direction of the dial (the red box in the picture). By walking in this direction we are now heading at 235 degrees, straight toward our purple landmark. As you are walking periodically check your compass to ensure you are still heading 235 degrees. To do this, follow the same aforementioned procedures.
What if we don't want to guesstimate? What if the journey to the purple marker is full of dangerous terrain and hundreds of miles away? Remember that being off by a few degrees at a close distance will not land you far from your mark; but the farther away you get, the bigger the difference becomes if you are not accurate.
This is where the compass truly shines, by precisely measuring azimuths. An azimuth is a fancy way of saying a compass bearing or "number to follow." With an azimuth and distance, you can precisely describe objects in relation to your position; for example:
"The market is about 7 miles away at a heading of 235".
These are clear enough directions for someone to follow and arrive at the destination. Don't worry about precisely measuring distance as we will cover that in Navigation Part 2 in great detail. For general purposes, one can calculate the speed of hiking and for how long to determine how far has been traveled.
Let's say we are trying to reach the purple marker; we see the marker way in the distance and we want to get a precise measurement. Here is how its done:
1. Deploy your compass as previously mention and point it towards the direction you want to go (the purple marker). Determine the bearing by looking down on your compass and determining the closest number that aligns with the target.
2. Place the cover at a 90 degree angle to the base and the eye piece at a 45 degree angle. Steady the compass with your support hand.
3. If you look through the cover, you will notice a "sighting wire" running vertically through a small window. Align the sighting wire with the top notch of the eye piece. Use this wire to "cut" your target (purple marker) in half. Without moving your hands, look through your eye piece window down at the face of the compass where a number will be displayed. This value will be your compass heading (235 degrees).
If you want to ensure the most precise navigation over long distances, once you confirmed the bearing of our target, find nearby objects that align with that bearing. For example in the straight line from here to the purple market there might be a tree about 100 yards away. Walk to the tree and take another bearing, find another object directly in line with your azimuth. This will ensure you always walk in a straight line by "frog hopping" from one "sub-target" to another.
Navigating Past an Obstacle
What if there is an obstacle between you and your destination? You can't just plow through it, but you also don't want to go run around it and risk loosing your compass bearing. Remember, following the same number bearing from different positions outside the line of your azimuth will land you slightly of course (the bigger the distance, the more you'll be so!) So what do we do?
We walk in squares!
Let's say the destination is the purple marker at a bearing of 235 degrees. We come across a massive obstacle that prevents us from going on a straight line.
Here, we take a 90 degree left turn (subtract 90 from 235 on the bearing), count the paces it takes us to walk to clear the obstacle, resume our 235 degree bearing until we clear the obstacle again, turn 90 degrees to the right (add 90 to the 235 bearing) and walk the same 20 paces as before to end in a straight line.
Now turn let 90 degrees to your original 235 and resume walking to your destination.
Hiking Anywhere Without Getting Lost
Let's say you are on a road trip and come across a patch of beautiful wilderness. You have a couple hours to spare so you decide to sling your pack and venture inside. But remember, you don't have a map and you've never been here before. How do you ensure you don't get lost?
A 180 degree turn from any bearing will lead us in the opposite way of that bearing. If you travel 3 miles at 0 degrees (North) and then travel 3 miles at 180 degrees (South) you will end up on the same spot. These applies for all bearings. All you have to do is add or subtract 180 degrees.
Remember that the only possible values you can get for a azimuth are between 0 and 360 degrees. So here is simple rule of thumb for find the back azimuth (the opposite direction of your bearing):
-If your original bearing is between 0 and 180 degrees, to go back, ADD 180 degrees. (Ex: 20 degrees has a back azimuth of 200 degrees) Notice the compass on the right. The 20 degree value is market by the red line, while directly 180 degrees across, the blue line marks 200 degrees.
-If your original bearing is between 181-360 degrees, SUBTRACT 180 degrees.
Its that simple! When heading into the unknown, the safest bet is to travel in straight lines for a predetermine distance or time, and then add or subtract 180 to each bearing traveled to head back.
Its very empowering to know how to venture into any wilderness without getting lost! I recommend bring a pen and paper and drawing your path and bearings to ensure you don't forget.
Learning how to navigate is among the most crucial survival skills you can have. Not only does it allow you to travel confidently in the wilderness but it can one day save your life! In the future we will cover advance navigation using topographical maps, triangulation, pace counting and planning expeditions; but with a solid base (and practice) of the topics in this article you will be more than ready to start exploring the woods.
Read this post as many times as necessary, get yourself a compass and get out there!
Author: Carlos Daniel Cortesi www.schoolofpracticalskill.com