Topographic Maps: "Grid Distance and Elevation" 1966 US Army Training Film

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• published: 25 Oct 2014
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more at http://search.quickfound.net/map_search_and_news.html Basic Map Reading Part II Grid, Distance and Elevation "USE OF MILITARY GRID SYSTEM TO LOCATE POSITIONS; USE OF GRAPHIC SCALES TO MEASURE DISTANCE; USE OF CONTOUR LINES TO IDENTIFY TOPOGRAPHIC DETAIL." US Army Training Film TF5-3719 see also: Direction, Orientation and Location with a Compass https://www.youtube.com/watch?v=nfDFqdqJe2o Public domain film from the National Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied. The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and equalization (the resulting sound, though not perfect, is far less noisy than the original). http://en.wikipedia.org/wiki/Topographic_map A topographic map is a type of map characterized by large-scale detail and quantitative representation of relief, usually using contour lines in modern mapping, but historically using a variety of methods. Traditional definitions require a topographic map to show both natural and man-made features. A topographic map is typically published as a map series, made up of two or more map sheets that combine to form the whole map. A contour line is a combination of two line segments that connect but do not intersect; these represent elevation on a topographic map. The Canadian Centre for Topographic Information provides this definition of a topographic map: A topographic map is a detailed and accurate graphic representation of cultural and natural features on the ground. Other authors define topographic maps by contrasting them with another type of map; they are distinguished from smaller-scale "chorographic maps" that cover large regions, "planimetric maps" that do not show elevations, and "thematic maps" that focus on specific topics. However, in the vernacular and day to day world, the representation of relief (contours) is popularly held to define the genre, such that even small-scale maps showing relief are commonly (and erroneously, in the technical sense) called "topographic". The study or discipline of topography, while interested in relief, is actually a much broader field of study which takes into account all natural and man made features of terrain. Topographic maps are based on topographical surveys. Performed at large scales, these surveys are called topographical in the old sense of topography, showing a variety of elevations and landforms. This is in contrast to older cadastral surveys, which primarily show property and governmental boundaries. The first multi-sheet topographic map series of an entire country, the Carte géométrique de la France, was completed in 1789. The Great Trigonometric Survey of India, started by the East India Company in 1802, then taken over by the British Raj after 1857 was notable as a successful effort on a larger scale and for accurately determining heights of Himalayan peaks from viewpoints over one hundred miles distant... United States The United States Geological Survey (USGS), a civilian Federal agency, produces several national series of topographic maps which vary in scale and extent, with some wide gaps in coverage, notably the complete absence of 1:50,000 scale topographic maps or their equivalent. The largest (both in terms of scale and quantity) and best-known topographic series is the 7.5-minute or 1:24,000 quadrangle. This scale is unique to the United States, where nearly every other developed nation has introduced a metric 1:25,000 or 1:50,000 large scale topo map. The USGS also publishes 1:100,000 maps covering 30 minutes latitude by one degree longitude, 1:250,000 covering one by two degrees, and state maps at 1:500,000 with California, Michigan and Montana needing two sheets while Texas has four. Alaska is mapped on a single sheet, at scales ranging from 1:1,584,000 to 1:12,000,000. Recent USGS digital US Topo 1:24,000 topo maps based on the National Map omit several important geographic details that were featured in the original USGS topographic map series (1945-1992). Examples of omitted details and features include power transmission lines, telephone lines, railroads, recreational trails, pipelines, survey marks, and buildings. For many of these feature classes, the USGS is working with other agencies to develop data or adapt existing data on missing details that will be included in The National Map and to US Topo. In other areas USGS digital map revisions may omit geographic features such as ruins, mine locations, springs, wells, and even trails in an effort to protect natural resources and the public at large, or because such features are not present in any public domain database...