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The National Map is a collaborative effort of the United States Geological Survey (USGS) and other federal, state, and local agencies to improve and deliver topographic information for the United States. [1]
The Libre Map Project is an online collection of all digital USGS 1:24K scale topographic maps (as well as various other GIS data) covering the United States, available as a free download. History [ edit ]
Topographic maps are also commonly called contour maps or topo maps. In the United States, where the primary national series is organized by a strict 7.5-minute grid, they are often called or quads or quadrangles. Topographic maps conventionally show topography, or land contours, by means of contour lines.
The largest (both in terms of scale and quantity) and best-known topographic series is the 7.5-minute, 1:24,000 scale, quadrangle, a non-metric scale virtually unique to the United States. Each of these maps covers an area bounded by two lines of latitude and two lines of longitude spaced 7.5 minutes apart.
Primarily from the United States Government Printing Office Style Manual. [1] State names usually signify only parts of each listed state, unless otherwise indicated. Based on the BLM manual's 1973 publication date, and the reference to Clarke's Spheroid of 1866 in section 2-82, coordinates appear to be in the NAD27 datum.
A "quadrangle" is a topographic map produced by the United States Geological Survey (USGS) covering the United States. The maps are usually named after local physiographic features. The shorthand " quad " is also used, especially with the name of the map; for example, "the Ranger Creek, Texas quad".
This scale is unique to the United States, [citation needed] 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 ...
The maps are produced by the USGS, which encourages the distribution of their maps through business partners. TopoZone offered aerial photographs from the USGS and street maps from the United States Census Bureau. In 2007 complete coverage of Canada was added, using the topographic map series produced by Natural Resources Canada.
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