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Episode 188 S5-25

Using a Compass


Special Guest:

Dark Days in Denver Ch 25

L. Douglas Hogan

In this chapter of Dark Days in Denver, Erika and her team are deep in the Denver battle. Earthquakes shake the foundations of buildings as the volcanic ash from Yellowstone mixes with the debris from the buildings falling. Visibility is limited and they must rely upon their compasses for direction. Here today to teach us the correct way to use a compass is L. Douglas Hogan, author of Oath Takers and The Tyrant Series. 

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You should always have a compass in your go bag and on your person if you are out hiking or in unfamiliar territory. L. Douglas Hogan recommends carrying a Commenga Model 27 Phosphorescent Lensatic Compass. This is the same style of compass that the US Military issues. It is time tested and can be used by itself or with a map.

There is a free floating dial in a compass. It actually floats in a liquid and must be held straight and flat. If you hold it at an angle, the dial will get stuck and it won't spin properly. The compass has a magnifying lens on one side and a slit with a line in the middle on the other side. When you line the lens up with the line and something in the distance, you will know the direction of that object. 

The compass has a magnet inside to make it function properly. If you place it on something that is metal, it will affect the magnetism so do not put your map on a vehicle and expect the compass to work properly on top of it.. Even rocks with a high iron content may affect the magnet. You can tell if the magnetism is being affected because the needle will be stuck.

To tell what direction you are headed, line up the lens with the line and an object. On the compass you will see mils and degrees. If you want to go east, move the compass until the line on the lens and east are perfectly in line and note an object in the distance. If you have to go, for example, 240 degrees east look at the degree marking and line that up with the line on the compass.

There are a few types of north that are used in navigation. Magnetic north is the spot on the earth where the north pole is located. This point moves and is affected by the earth's core. Every reading on a compass gives you magnetic north. True north has nothing to do with magnetic north. True north corresponds to the latitude lines that you will find on an atlas. It is a straight line drawn from the southern most tip of the planet to the northern most tip. Grid north are the lines on a map. True north lines are curved if drawn on a flat surface due to the curvature of the planet. In order to correct that defect, map makers draw a grid on a map. Grid north and magnetic north are the two norths that you use to read a map.

 When you are traveling without a compass, you will always travel in a circle because one of your feet is dominant over the other. 

When using a map you have to account for declination. The declination diagram is shown on the bottom of your map. The declination diagram shows grid north with magnetic north and true north. The line with a star is always magnetic north and the line with an arrow is grid north. The grid north line will lean east or west, depending on where you are in the world. If it leans west, that is a negative declination and if it leans east, that is a positive declination. There are 360 degrees on a compass. If your reading is 0-180 degrees, that's a positive declination. If your reading is 181-360 degrees, that's a negative declination. If your magnetic north is a negative declination you have to add the degrees to find the correct declination. For example, to find a declination that is 19 degrees west of magnetic north, you have to add nineteen degrees to magnetic north to fix your reading for grid north.

The declination shows you the difference between grid north and magnetic north. Magnetic north changes. Maps must be updated and old maps will not work. On the declination diagram if magnetic north is west, add the degrees. If it is east, subtract the degrees. On the east coast, you will almost always have a positive declination and on the west coast, you will have a negative declination.

The reading you take from a compass is called an Azimuth. point your compass at a location you want to reach. For example, you point your compass at an object or person sent out into the distance and they are 240 degrees southwest. That is your Azimuth reading. 

There are some objects you should have for navigating along with your compass. You should carry a protractor, a ruler, laminated maps showing your bug out locations and a grease pen. 

To find out where you are on a map you need to resection or do a reverse Azimuth. Find two objects on a map that you can also visually see. It could be a building, a river bend, a mountain, etc. For our example we are going to use a church. Point your compass at it and get a reading. Say it's 240 degrees east (remember to add or subtract for your declination). Find your second location. For our example, lets use a river bend. Get your reading, and declinate. Say it's 100 degrees west. Take your protractor and put the little hole in the middle on the church. Do a reverse azimuth of your reading. If you have a number less than 180 degrees, you have to add 180 degrees. If you have a reading greater than 180 degrees, you have to subtract 180 degrees. 

Lets see how this works with our example. The church was 240 degrees east. You subtract 180 degrees to get a reading of sixty degrees. Find 60 degrees on your protractor that is placed on the church and draw a line from the church 60 degrees west. Find the river bend on the map that was 100 degrees west. Get your reverse azimuth. Since 100 degrees is less than 180 degrees, we add 180 degrees to get 280 degrees. Put your protractor on the river bend and draw a line 280 degrees west. Where the lines intersect is where you are.

When hiking in the wilderness, it can be hard to find land markers. Use the compass to ensure you are walking in a straight line. Topographical maps can help you locate landmarks because they show elevation. 

If you get lost, go in one direction. Try to locate a stream, especially a large one and follow it. Most of the time streams will lead you to civilization. 

Make sure to practice, practice, practice. This is not a skill you want to be learning when you need to rely upon it. Don't rely on electronics! Make sure you know how to use a compass and a map. 

Here is a link to a video that Doug recommends for learning this information:

Commenga Phosphorescent Lensatic Compass 27
Commenga Phosphorescent Lensatic Compass 27
Declination Diagram
Declination Diagram

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Dark Days in Denver Ch 25

L. Douglas Hogan

L. Douglas Hogan is a U.S.M.C. veteran with over twenty years in public service. Among these are three years as an anti-tank infantryman, one year as a Marine Corps Marksmanship Instructor, ten years as a part-time police officer, and seventeen years working in state government doing security work and supervision. He is the best-selling author of “Oath Takers”, has authored four books in a series titled Tyrant, and is working on the sixth a final book of the series. He has been married over twenty years, has two children, and is faithful to his church, where he resides in southern Illinois.

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