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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 ]
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". A quadrangle is defined by north and south ...
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.
Today's U.S. Topo quadrangle (1:24,000) maps are mass-produced, using automated and semiautomated processes, with cartographic content supplied from the National GIS Database. [33] In the two years from June 2009 to May 2011, the USGS produced nearly 40,000 maps, more than 80 maps per work day. [33]
A digital orthophoto quadrangle [1] (DOQ) is aerial photography or satellite imagery that has been corrected so that its pixels are aligned with longitude and latitude lines, and have a narrowly defined region of coverage. This is a widely used format introduced by United States Geological Survey (USGS). [1]
Image of the Coprates Quadrangle (MC-18). The prominent Valles Marineris chasma system intersects the moderately cratered northern part and the faulted highland ridged plains in the southern part. The Coprates quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research ...
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.
Map produced with DLG data. DLGs are normally derived from USGS maps or USGS map-related sources. DLGs are distributed at three different scales: large-scale, which normally correspond to the USGS 7.5- by 7.5-minute, 1:24,000 and 1:25,000-scale topographic quadrangle map series, 1:63,360-scale for Alaska and 1:30,000-scale for Puerto Rico; intermediate scale, which are derived from the USGS 30 ...