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Military personnel need a way of expressing direction that is accurate, is adaptable to any part of the world, and has a common unit of measure. Directions are expressed as units of angular measure.
a. Degree. The most common unit of measure is the degree (°) with its subdivisions of minutes (') and seconds (").
1 degree = 60 minutes.
1 minute = 60 seconds.
b. Mil. Another unit of measure, the mil (abbreviated ), is used mainly in artillery, tank, and mortar gunnery. The mil expresses the size of an angle formed when a circle is divided into 6,400 angles, with the vertex of the angles at the center of the circle. A relationship can be established between degrees and mils. A circle equals 6400 mils divided by 360 degrees, or 17.78 mils per degree. To convert degrees to mils, multiply degrees by 17.78.
c. Grad. The grad is a metric unit of measure found on some foreign maps. There are 400 grads in a circle (a 90-degree right angle equals 100 grads). The grad is divided into 100 centesimal minutes (centigrads) and the minute into 100 centesimal seconds (milligrads).
In order to measure something, there must always be a starting point or zero measurement. To express direction as a unit of angular measure, there must be a starting point or zero measure and a point of reference These two points designate the base or reference line. There are three base lines—
true north, magnetic north, and grid north. The most commonly used are magnetic and grid.
a. True North. A line from any point on the earth's surface to the north pole. All lines of longitude are true north lines. True north is usually represented by a star (Figure 6-1).
Figure 6-1. Three norths.
b. Magnetic North. The direction to the north magnetic pole, as indicated by the north-seeking needle of a magnetic instrument. The magnetic north is usually symbolized by a line ending with half of an arrowhead (Figure 6-1). Magnetic readings are obtained with magnetic instruments, such as lensatic and M2 compasses.
c. Grid North. The north that is established by using the vertical grid lines on the map. Grid north may be symbolized by the letters GN or the letter "y" (Figure 6-1).
Return to DIRECTION
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The Long Walk by Slavomir Rawicz
In 1941, the author and a small group of fellow prisoners escaped a Soviet labor
camp. Their march out of Siberia, through China, the Gobi Desert, Tibet, and over
the Himalayas to British India is a remarkable statement about man's desire to be
free. Buy it at Amazon.com
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Books
Buy the book this website is based on: Map Reading and
Land Navigation
This website is based on the US Army Field Manual: "Map Reading and Land Navigation"
Buy a copy from Amazon.com to take with you out in the field.
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One of the best ways to learn and become proficient in any subject is to find a way to make a game or sport of it. That's exactly what orienteering does! Orienteering began to develop almost 100 years ago in the Scandinavian countries as a fun and effective method for military training in land navigation. Bjorn Kjellstrom was closely involved with the early development of orienteering, and he is the person who introduced the sport to North America. He, along with his brother Alvar, and a friend named Gunnar Tillander, invented the modern orienteering compass. They manufactured and marketed it as the Silva Protractor compass. This compass, along with Bjorn's book Be Expert with
Map and Compass, made it much easier for anyone to learn how to use a map and compass.
This book has become the most widely read classic on the subject of map reading, compass use, and orienteering. Over 500,000 copies have been sold in the english language editions alone. There have been very successful editions published in French, Italian, and other languages as well. It is a short (just over 200 pages), easy to read, enjoyable book that can help you to have fun while you learn the subject quickly and effectively.
The book is organized into four main parts, plus a short, useful introduction. Part 1 covers having fun with maps alone. Then, Part 2 covers having fun with a compass alone. Part 3 puts it together and shows you how to have fun with a map and compass together. This section also introduces the game or sport of orienteering. Part 4 covers competitive orienteering for those who would like to compete with others in the sport.
A reproduction of a segment of an actual topographic map is included as a fold-out in the back of the book. It is used together with the "how-to" instructions the book provides. For example, one of the exercises in Part 3 is an imaginary orienteering "hike" that uses the sample map.
If you would like to have one of the best books available on map reading and using a compass,
Be Expert with
Map and Compass is hard to beat. You can buy a copy from Amazon.com today.
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