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From approximately 1947–1992, the USGS produced the 7.5 minute series, with each map covering an area one-quarter of the older 15-minute quad series, which it replaced. [1] A 7.5 minute quadrangle map covers an area of 49 to 70 square miles (130 to 180 km 2). [2] Both map series were produced via photogrammetric analysis of aerial photography ...
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.
During the registration process, prospective volunteers submitted a list of the 7.5 minute quadrangle maps on which they wished to work. Once accepted into the project, volunteers received their assignment and 1:24,000 scale topographic map of their quad. While there was no deadline for completing maps, the project's administrators preferred ...
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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.
DOQs produced by the USGS cover an area measuring 7.5-minutes longitude by 7.5-minutes latitude (the same area covered by a USGS 1:24,000-scale topographic map, also known as a 7.5-minute quadrangle) or 3.75-minutes by 3.75-minutes.
USGS Maps. Every USGS topographic map available for free download from the Internet Archive. OpenStreetMap - CC-BY-SA 2.0 vector map data collected by GPS; The Map Library - Maps for Central America and Africa. Tag with commons:Template:PD-MapLibrary (talk, backlinks, edit) GinkgoMaps - Free Digital Maps published under the CC-by Licence
The Libre Map Project was started by Jared Benedict and around 100 additional individuals contributing money to purchase (or "liberate") a full set of 1:24K scale USGS topographic maps in Digital raster graphic form. [1] The map files were then hosted by archive.org to ensure the map data will continue to be freely available to everyone ...
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