MSL101L04 Basic Map Reading SR.pdf lesson 4.pdf

Map distance representative fraction scale ground

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map distance Representative fraction (scale) = ------------------------- ground distance 2-10. As the denominator of the representative fraction gets larger and the ratio gets smaller, the scale of the map decreases. NGA maps are classified by scale into three categories: small-, medium-, and large- scale maps. (See Figure 2-1.) The terms small scale , medium scale , and large scale may be confusing when read in conjunction with the number. However, when viewing the number as a fraction, it quickly becomes apparent that 1:600,000 of something is smaller than 1:75,000 of the same thing. Therefore, the larger the number after 1, the smaller the scale of the map. Maps can be categorized as— Small . Maps with scales of 1:1,000,000 and smaller are used for general planning and for strategic studies (bottom map in Figure 2-1). The standard small-scale map is 1:1,000,000. This map covers a large land area at the expense of detail. Medium . Maps with scales between 1:1,000,000 and 1:75,000 are used for operational planning (center map in Figure 2-1). They contain a moderate amount of detail, but terrain analysis is best done with the large-scale maps. The standard medium-scale map is 1:250,000. Medium-scale maps of 1:100,000 are encountered frequently. Large . Maps with scales of 1:75,000 and larger are used for tactical, administrative, and logistical planning (top map in Figure 2-1). These are the maps a Soldier or junior leader are most likely to encounter. The standard large-scale map is 1:50,000; however, many areas have been mapped at a scale of 1:25,000.
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Chapter 2 2-4 TC 3-25.26 15 November 2013 Figure 2-1. Scale classifications Types . The map of choice for land navigators is the 1:50,000-scale military topographic map. When operating in foreign places, some NGA map products may not cover a particular area of operations due to a lack of production, or may not be available to a unit when required. Therefore, units may find it necessary to use maps produced by foreign governments that may or may not meet the standards for accuracy set by NGA. These maps often use symbols that resemble those found on NGA maps but have completely different meanings. There may be other times units use obtained maps such as tourist maps or other commercially produced maps. (In Grenada, many of our troops used a British tourist map.) It is also important to know how to use the many other products available from the NGA: Planimetric map. A planimetric map presents only the horizontal positions for the features represented. It is distinguished from a topographic map by the omission of relief, normally represented by contour lines. Sometimes it is called a line map. Topographic map. A topographic map portrays terrain features in a measurable way, as well as the horizontal positions of the features represented. The vertical positions, or relief, are normally represented by contour lines on military topographic maps. On maps showing relief, the elevations and contours are measured from a specific vertical datum plane, usually mean sea level.
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  • Fall '16
  • Cartography, Geographic coordinate system, Topographic map, Universal Transverse Mercator coordinate system

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