![]() ![]() In this case, it is the upper index contour line numbered 600. The elevation of point (a) is 540 meters the elevation has increased.Į. The contour interval is 20 meters ( Figure 10-2), thus each one of the intermediate contour lines crossed to get to point (a) adds 20 meters to the 500-meter index contour line. Locate point (a) on the second intermediate contour line above the 500-meter index contour line. Determine the exact elevation of point (a), start at the index contour line numbered 500 and count the number of intermediate contour lines to point (a). Going from the lower to the upper index contour line shows an increase in elevation.ĭ. The upper index contour line is numbered 600, or 600 meters. The lower index contour line is numbered 500, which means any point on that line is at an elevation of 500 meters above mean sea level. In Figure 10-3, point (a) is between the index contour lines. Determine if you are going from lower elevation to higher, or vice versa. Find the numbered index contour line nearest the point of which you are trying to determine the elevation ( Figure 10-3).Ĭ. Determine the contour interval and the unit of measure used, for example, feet, meters, or yards ( Figure 10-2).ī. To determine the elevation of a point on the map-Ī. The contour interval measurement given in the marginal information is the vertical distance between adjacent contour lines. CONTOUR INTERVALSīefore the elevation of any point on the map can be determined, the user must know the contour interval for the map he is using. These lines are normally found where there is very little change in elevation, such as on fairly level terrain. They show changes in elevation of at least one-half the contour interval. There are normally four intermediate contour lines between index contour lines. These lines are finer and do not have their elevations given. The contour lines falling between the index contour lines are called intermediate contour lines. This number is the elevation of that line. Normally, each index contour line is numbered at some point. Starting at zero elevation or mean sea level, every fifth contour line is a heavier line. The three types of contour lines ( Figure 10-1) used on a standard topographic map are as follows: The elevation represented by contour lines is the vertical distance above or below sea level. ![]() All points on the contour line are at the same elevation. A contour line represents an imaginary line on the ground, above or below sea level. Contour lines are the most common method of showing relief and elevation on a standard topographic map. Hachures are used extensively on small-scale maps to show mountain ranges, plateaus, and mountain peaks.Į. They do not represent exact elevations, but are mainly used to show large, rocky outcrop areas. Hachures are sometimes used with contour lines. Hachures are short, broken lines used to show relief. Shaded relief is sometimes used in conjunction with contour lines to emphasize these features.ĭ. The darker the shading, the steeper the slope. Relief shading indicates relief by a shadow effect achieved by tone and color that results in the darkening of one side of terrain features, such as hills and ridges. Form lines are represented on a map as dashed lines and are never labeled with representative elevations.Ĭ. Form lines have no standard elevation and give only a general idea of relief. Form lines are not measured from any datum plane. However, this method does not allow the map user to determine the exact elevation of a specific point-only the range.ī. A legend is printed on the map margin to indicate the elevation range represented by each color. Each shade of color, or band, represents a definite elevation range. A different color is used for each band of elevation. Layer tinting is a method of showing relief by color. Mapmakers use several methods to depict relief of the terrain.Ī. Relief is the representation (as depicted by the mapmaker) of the shapes of hills, valleys, streams, or terrain features on the earth’s surface. Elevation of a point on the earth’s surface is the vertical distance it is above or below mean sea level. The reference or start point for vertical measurement of elevation on a standard military map are the datum plane or mean sea level, the point halfway between high tide and low tide. ![]() To do this, they must first understand how the mapmaker indicated the elevation and relief on the map. They must also be able to determine the elevation and relief of areas on standard military maps. Soldiers must know how to determine locations of points on a map, measure distances and azimuths, and identify symbols on a map. The elevation of points on the ground and the relief of an area affect the movement, positioning, and, in some cases, effectiveness of military units. ![]()
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