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A quadrangle is defined by north and south boundaries of constant latitude (which are not great circles so are curved), and by east and west boundaries of constant longitude. 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 ...
In 2008 the USGS abandoned traditional methods of surveying, revising, and updating topographic maps based on aerial photography and field checks. [34] 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. [34]
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 ...
The USGS also utilizes data from The National Map Corps, which consists of volunteers who devote some of their time to provide cartographic information on structures. [4] The National Map is the official replacement for the USGS topographic map program. [5]
Figure 1. This BLM map depicts the principal meridians and baselines used for surveying states (colored) in the PLSS.. The following are the principal and guide meridians and base lines of the United States, with the year established and a brief summary of what areas' land surveys are based on each.
USGS Topographic maps are downloadable as pdf files from a searchable map or by a search if the map name is known. How a Topographic Map is Manufactured, History, and Other Information; The International Cartographic Association (ICA) Commission on Topographic Mapping
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]
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