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Contents

1. Training strategy
2. Maps
3. Marginal information and symbols
4. Grids
5. Scale and distance
6. Direction
7. Overlays
8. Aerial photographs
9. Navigation equipment and methods
10. Elevation and relief
  - Definitions
  - Methods of depicting relief
  - Contour intervals
  - Types of slopes
  - Percentage of slope
  - Terrain features
  - Interpretation of terrain features
  - Profiles
11. Terrain association
12. Mounted land navigation
13. Navigation in different types of terrain
14. Unit sustainment

A. Field sketching
B. Map folding techniques
C. Units of measure and conversion factors
D. Joint operations graphics
E. Exportable training material
F. Orienteering
G. M2 compass
H. Additional aids
I. Foreign maps
J. Global positioning system
K. Precision lightweight global positioning system receiver

Survival Gear

Handheld GPS
Specialty Outdoor Gear
Digital Compasses
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Hunting and Fishing Magazines

10-5. PERCENTAGE OF SLOPE

The speed at which personnel and equipment can move up or down a hill is affected by the slope of the ground and the limitations of the equipment. Because of this, a more exact way of describing a slope is necessary.

a.   Slope may be expressed in several ways, but all depend upon the comparison of vertical distance (VD) to horizontal distance (HD) (Figure 10-10). Before we can determine the percentage of a slope, we must know the VD of the slope. The VD is determined by subtracting the lowest point of the slope from the highest point. Use the contour lines to determine the highest and lowest point of the slope (Figure 10-11).

Figure 10-10. Slope diagram.

Figure 10-10. Slope diagram.

 

Figure 10-11. Contour line around a slope.

Figure 10-11. Contour line around a slope.

b.   To determine the percentage of the slope between points (a) and (b) in Figure 10-11, determine the elevation of point (b) (590 meters). Then determine the elevation of point (a) (380 meters). Determine the vertical distance between the two points by subtracting the elevation of point (a) from the elevation of point .The difference (210 meters) is the VD between points (a) and (b). Then measure the HD between the two points on the map in Figure 10-12. After the horizontal distance has been determined, compute the percentage of the slope by using the formula shown in Figure 10-13.

Figure 10-12. Measuring horizontal distance.

Figure 10-12. Measuring horizontal distance.

 

Figure 10-13. Percentage of slope in meters.

Figure 10-13. Percentage of slope in meters.

c.   The slope angle can also be expressed in degrees. To do this, determine the VD and HD of the slope. Multiply the VD by 57.3 and then divide the total by the HD (Figure 10-14). This method determines the approximate degree of slope and is reasonably accurate for slope angles less than 20.

Figure 10-14. Degree of slope.

Figure 10-14. Degree of slope.

d.   The slope angle can also be expressed as a gradient. The relationship of horizontal and vertical distance is expressed as a fraction with a numerator of one (Figure 10-15).

Figure 10-15. Gradient.

Figure 10-15. Gradient.



Elevation and relief
Definitions | Methods of depicting relief | Contour intervals | Types of slopes | Percentage of slope | Terrain features | Interpretation of terrain features | Profiles |




Buy The Book This Site Is Based On
The 'Land Navigation' section of this site is based on 'Map Reading and Land Navigation', a public domain work published by the U.S. Department of Defense that is available for sale at Amazon.com.




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