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Geological Survey: Difference between revisions
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===Topographic mapping=== | ===Topographic mapping=== | ||
[[File:Mount Marcy New York USGS topo map 1892.jpg|thumb|An 1892 15-minute map of [[Mount Marcy]] in the [[Adirondacks]] in [[New York (state)|New York state]] from the late 19th century]] | [[File:Mount Marcy New York USGS topo map 1892.jpg|thumb|An 1892 15-minute map of [[Mount Marcy]] in the [[Adirondacks]] in [[New York (state)|New York state]] from the late 19th century]] | ||
The USGS produces several national series of [[topographic maps]] which vary in [[scale (map)|scale]] and extent, with some wide gaps in coverage, notably the complete absence of 1:50,000 scale topographic maps or their equivalent. The largest (both in terms of scale and quantity) and best-known topographic series is the 7.5-minute, 1:24,000 scale, [[Quadrangle (geography)|quadrangle]], a non-metric scale virtually unique to the United States. Each of these maps covers an area bounded by two lines of | The USGS produces several national series of [[topographic maps]] which vary in [[scale (map)|scale]] and extent, with some wide gaps in coverage, notably the complete absence of 1:50,000 scale topographic maps or their equivalent. The largest (both in terms of scale and quantity) and best-known topographic series is the 7.5-minute, 1:24,000 scale, [[Quadrangle (geography)|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 [[minute of arc|minutes]] apart. Nearly 57,000 individual maps in this series cover the [[Continental United States|48 contiguous states]], [[Hawaii]], [[United States Territories|U.S. territories]], and areas of [[Alaska]] near [[Anchorage]], [[Fairbanks]], and [[Prudhoe Bay]]. The area covered by each map varies with the latitude of its represented location due to convergence of the meridians. At lower latitudes, near 30° north, a 7.5-minute quadrangle contains an area of about {{convert|64|sqmi|km2|0}}. At 49° north latitude, {{convert|49|sqmi|km2|0}} are contained within a quadrangle of that size. As a unique non-metric map scale, the 1:24,000 scale naturally requires a separate and specialized [[romer]] scale for plotting map positions.<ref name="USGS">{{cite web|url=http://topomaps.usgs.gov/|title=USGS – Topographic Maps|first=USGS Rolla|last=Missouri|website=Topomaps.usgs.gov|access-date=April 30, 2017|archive-url=https://web.archive.org/web/20090412214110/http://topomaps.usgs.gov/|archive-date=April 12, 2009|url-status=dead|df=mdy-all}}</ref><ref>{{cite web|url=http://erg.usgs.gov/isb/pubs/booklets/usgsmaps/usgsmaps.html|title=USGS Maps Booklet|website=erg.usgs.gov|access-date=2017-04-30|archive-date=June 2, 2008|archive-url=https://web.archive.org/web/20080602185425/http://erg.usgs.gov/isb/pubs/booklets/usgsmaps/usgsmaps.html|url-status=dead}}</ref> In recent years, budget constraints have forced the USGS to rely on donations of time by civilian volunteers in an attempt to update its 7.5-minute topographic map series, and USGS stated outright in 2000 that the program was to be phased out in favor of ''[[The National Map]]''<ref>{{cite web |url= http://thor-f5.er.usgs.gov/topomaps/revision_overview.pdf |title= The U.S. Geological Survey's Revision Program for 7.5-Minute Topographic Maps |first= Larry |last= Moore |publisher= United States Geological Survey |date= December 2000 |access-date= June 17, 2010 |archive-date= February 13, 2013 |archive-url= https://web.archive.org/web/20130213213923/http://thor-f5.er.usgs.gov/topomaps/revision_overview.pdf |url-status= dead }}</ref> (not to be confused with the [[National Atlas of the United States]] produced by the [[United States Department of the Interior|Department of the Interior]], one of whose bureaus is USGS). | ||
An older series of maps, the 15-minute series, was once used to map the contiguous 48 states at a scale of 1:62,500 for maps covering the continental United States, but was discontinued during the last quarter of the twentieth century. Each map was bounded by two [[Circle of latitude|parallels]] and two [[Meridian (geography)|meridians]] spaced 15 minutes apart—the same area covered by four maps in the 7.5-minute series. The 15-minute series, at a scale of 1:63,360 (one inch representing one mile), remains the primary topographic quadrangle for the state of Alaska (and only for that particular state). Nearly 3,000 maps cover 97% of the state.<ref name="USGS" /> The United States remains virtually the only developed country in the world without a standardized civilian topographic map series in the standard 1:25,000 or 1:50,000 metric scales, making coordination difficult in border regions (the U.S. military does issue 1:50,000 scale topo maps of the continental United States, though only for use by members of its defense forces). | An older series of maps, the 15-minute series, was once used to map the contiguous 48 states at a scale of 1:62,500 for maps covering the continental United States, but was discontinued during the last quarter of the twentieth century. Each map was bounded by two [[Circle of latitude|parallels]] and two [[Meridian (geography)|meridians]] spaced 15 minutes apart—the same area covered by four maps in the 7.5-minute series. The 15-minute series, at a scale of 1:63,360 (one inch representing one mile), remains the primary topographic quadrangle for the state of Alaska (and only for that particular state). Nearly 3,000 maps cover 97% of the state.<ref name="USGS" /> The United States remains virtually the only developed country in the world without a standardized civilian topographic map series in the standard 1:25,000 or 1:50,000 metric scales, making coordination difficult in border regions (the U.S. military does issue 1:50,000 scale topo maps of the continental United States, though only for use by members of its defense forces). | ||