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Depending on the military mission, soldiers may need to determine not only the height of a hill, but the degree of the hill's slope as well. The rate of rise or fall of a terrain feature is known as its slope. The speed at which equipment or personnel can move is affected by the slope of the ground or terrain feature. This slope can be determined from the map by studying the contour lines—the closer the contour lines, the steeper the slope; the farther apart the contour lines, the gentler the slope. Four types of slopes that concern the military are as follows:
a. Gentle. Contour lines showing a uniform, gentle slope will be evenly spaced and wide apart (Figure 10-6). Considering relief only, a uniform, gentle slope allows the defender to use grazing fire. The attacking force has to climb a slight incline.
Figure 10-6. Uniform, gentle slope.
b. Steep. Contour lines showing a uniform, steep slope on a map will be evenly spaced, but close together. Remember, the closer the contour lines, the steeper the slope (Figure 10-7). Considering relief only, a uniform, steep slope allows the defender to use grazing fire, and the attacking force has to negotiate a steep incline.
Figure 10-7. Uniform, steep slope.
c. Concave. Contour lines showing a concave slope on a map will be closely spaced at the top of the terrain feature and widely spaced at the bottom (Figure 10-8). Considering relief only, the defender at the top of the slope can observe the entire slope and the terrain at the bottom, but he cannot use grazing fire. The attacker would have no cover from the defender's observation of fire, and his climb would become more difficult as he got farther up the slope.
Figure 10-8. Concave slope.
d. Convex. Contour lines showing a convex slope on a map will be widely spaced at the top and closely spaced at the bottom (Figure 10-9). Considering relief only, the defender at the top of the convex slope can obtain a small distance of grazing fire, but he cannot observe most of the slope or the terrain at the bottom. The attacker will have concealment on most of the slope and an easier climb as he nears the top.
Figure 10-9. Convex slope.
Return to Elevation and Relief
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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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