Topographic maps show three-dimensional features on a two-dimensional surface.
Topographical maps use contour lines to represent three-dimensional elevation changes in the physical features of landscapes. Topographic maps are used by a variety of professions, including urban and regional planners, outdoor and land management professionals and armed forces. The main difference between topographic map types is the scale used to draw the map.
7.5-Minute Quads
The United States Geological Survey (USGS) 7.5-minute quadrangle maps are drawn at a scale of 1:24,000 comparing what is represented on the map to real life, translating to every inch of the map to equal 2,000 feet in real life. These maps are used by civil engineers and outdoor recreation professionals. The USGS offers quadrangles for the conterminous 48 states, Hawaii, urban centers in Alaska and U.S. territories. There are 57,000 maps available through the USGS, as of May 2011, covering all of the land area of the U.S. The 7.5-minute quads using metric units are available at a scale of 1:25,000.
GPS Maps
Multiple global positioning satellite (GPS) system maps have topographic features. Because of advanced GPS technology, these maps can be zoomed in or out to show extremely accurate details or broad overviews of a given area. Computer software programs also allow you to print topographic maps from your GPS unit to be used for geocaching or other recreational options. Some of these software programs will also allow you to email and customize maps by marking certain locations or writing annotations to the map itself.
National Geographic Maps
National Geographic topographic maps are available in printed versions through outdoor retail stores or through electronic versions through the National Geographic Topo Software, which is sold by individual states and regions. Printed maps use a 1:64,000 scale, equating one inch on the map to 1.1 mile in real life. National Geographic maps are useful for outdoor recreation purposes and have updated trail profiles that are more reliable than USGS maps, which often have outdated trail locations because of the costly nature of remapping wilderness areas around the country.
1- and 2-Degree Sheets
The USGS also makes various other sizes, including 1- and 2-degree map sheets. The 1-degree sheet shows one degree of longitude and 30 minutes of latitude, which roughly equals 16 of the 7.5-minute quadrangles. The 1-degree sheet uses a scale degree of 1:100,000, which is useful for large-scale planning on urban and regional levels. The 2-degree sheet has a scale of 1:250,000 and equals about four of the 1-degree sheets.
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