Map Reading and Land Navigation by unknow

Author:unknow
Language: eng
Format: epub
Published: 2017-05-29T16:00:00+00:00

Different Types of Maps Explained

Types of regular maps and also map substitutes

The map of choice for land navigators is the 1:50,000-scale military topographic map. It is important, however, to know how to use the many other products available from the NGA as well. When operating in foreign places, you may discover that NGA map products have not yet been produced to cover your particular area of operations, or they may not be available to your unit when you require them. Therefore, you must be prepared 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 which have completely different meanings. There may be other times when you must operate with any map you can obtain. This might be a commercially produced map run off on a copy machine at higher headquarters. In Grenada, many of our troops used a British tourist map.

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.

Photomap. A photomap is a reproduction of an aerial photograph upon which grid lines, marginal data, place names, route numbers, important elevations, boundaries, and approximate scale and direction have been added.

Joint Operations Graphics. Joint operations graphics are based on the format of standard 1:250,000 medium-scale military topographic maps, but they contain additional information needed in joint air-ground operations. Along the north and east edges of the graphic, detail is extended beyond the standard map sheet to provide overlap with adjacent sheets. These maps are produced both in ground and air formats. Each version is identified in the lower margin as either joint operations graphic (air) or joint operations graphic (ground). The topographic information is identical on both, but the ground version shows elevations and contour in meters and the air version shows them in feet. Layer (elevation) tinting and relief shading are added as an aid to interpolating relief. Both versions emphasize airlanding facilities (shown in purple), but the air version has additional symbols to identify aids and obstructions to air navigation.

Photomosaic. A photomosaic is an assembly of aerial photographs that is commonly called a mosaic in topographic usage. Mosaics are useful when time does not permit the compilation of a more accurate map. The accuracy of a mosaic depends on the method employed in its preparation and may vary from simply a good pictorial effect of the ground to that of a planimetric map.

Terrain Model. A terrain model is a scale model of the terrain showing features, and in large-scale models showing industrial and cultural shapes.

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