MSL101L04 Basic Map Reading SR.pdf lesson 4.pdf

Maps of the polar regions south of 80 degrees south

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Maps of the polar regions (south of 80 degrees south and north of 84 degrees north) at 1:1,000,000 and larger scales are based on the polar stereographic projection. The note reads POLAR STEREOGRAPHIC PROJECTION. Vertical datum note (16). The vertical datum note is located in the center of the lower margin. The vertical datum or vertical-control datum is defined as a level surface taken as a surface of reference from which to determine elevations. In the United States, Canada, and Europe, the vertical datum refers to the mean sea level surface. However, in parts of Asia and Africa, the vertical-control datum may vary locally and is based on an assumed elevation that has no connection to the sea level surface. Map readers should habitually check the vertical datum note
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Marginal Information and Symbols 15 November 2013 TC 3-25.26 3-3 on maps, particularly if the map is used for low-level aircraft navigation, naval gunfire support, or missile target acquisition. Horizontal datum note (17). The horizontal datum note is located in the center of the lower margin. The horizontal datum or horizontal-control datum is defined as a geodetic reference point (of which five quantities are known: latitude, longitude, azimuth of a line from this point, and two constants, which are the parameters of reference ellipsoid). These are the basis for horizontal-control surveys. The horizontal-control datum may extend over a continent or be limited to a small local area. Maps and charts produced by NGA are produced on 32 different horizontal-control data. Map readers should habitually check the horizontal datum note on every map or chart, especially adjacent map sheets, to ensure the products are based on the same horizontal datum. If products are based on different horizontal-control data, coordinate transformations to a common datum is performed. UTM coordinates from the same point computed on different data may differ as much as 900 meters (m). Control note (18). The control note is located in the center of the lower margin. It indicates the special agencies involved in the control of the technical aspects of all the information that is disseminated on the map. Preparation note (19). The preparation note is located in the center of the lower margin. It indicates the agency responsible for preparing the map. Printing note (20). The printing note is also located in the center of the lower margin. It indicates the agency responsible for printing the map and the date the map was printed. The printing data should not be used to determine when the map information was obtained. Grid reference box (21). The grid reference box is normally located in the center of the lower margin. It contains instructions for composing a grid reference. Unit imprint and symbol (22). The unit imprint and symbol is on the left side of the lower margin identifies the agency that prepared and printed the map and its respective symbol. This information is important to the map user in evaluating the reliability of the map.
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  • Fall '16
  • Cartography, Geographic coordinate system, Topographic map, Universal Transverse Mercator coordinate system

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