What do the different north arrows on a USGS topographic map mean?
A diagram at the bottom of most USGS topographic maps shows three north arrows--true north, grid north, and magnetic north--and the angles between them. Some maps, especially very old maps, do not have this diagram.
True north, also called geodetic north or geographic north, is the direction of the line of longitude that bisects the quadrangle. All longitude lines converge to points at the north and south poles. The star symbol in the diagram indicates true north.
Magnetic north (MN) shows the direction a magnetic compass would point at the time the map was published. The direction of magnetic north varies over time and with the position on the earth's surface, so magnetic declination values on old maps might no longer be accurate. Magnetic declination values shown on current maps are obtained from NOAA's National Geophysical Data Center.
Grid north (GN) is the direction of a plane grid system, usually the grid associated with the map projection. On current US Topo maps, the projection is Transverse Mercator and the plane grid is Universal Transverse Mercator (UTM). All US Topo maps have a 1,000-meter UTM grid included on the map; the angle at which this grid meets the map projection line visually shows the difference between true and grid north. Historical topographic maps might relate grid north to other grid systems. The difference between true north and grid north is an inherent effect of transforming the earth's spherical surface to a plane surface. The size of this difference for a particular map depends on the projection and the map location relative to the projection origin.
Related Content
How do I find, download, or order topographic maps?
The U.S. Geological Survey (USGS) has been the primary civilian mapping agency of the United States since 1879. Some of the most well-known USGS maps are the 1:24,000-scale topographic maps, also called 7.5-minute quadrangles . In 2009, the USGS transitioned from our hand scribed historical topographic maps to US Topos , which are computer-generated on a regular schedule using national databases...
Are USGS topographic maps copyrighted?
All topographic maps produced by the U.S. Geological Survey (USGS) are in the public domain and are not copyrighted except for the following three cases that apply only to US Topo maps (produced 2009-present): Most maps in the period 2010-2016 contain commercially licensed road data (see note below). Orthoimages in Alaska are commercially licensed. Orthoimages in Hawaii were commercially licensed...
Can I still get the older topographic maps?
Yes. Topographic maps originally published as paper documents between 1884-2006 have been scanned and published as the USGS Historical Topographic Map Collection . Download our historical topographic maps and our more current US Topo maps (published 2009-present) free of charge using TopoView (GeoPDF, GeoTIFF, JPEG, and KMZ formats) or using the USGS Store’s Map Locator (GeoPDF format). Order...
What is a topographic map?
The distinctive characteristic of a topographic map is the use of elevation contour lines to show the shape of the Earth's surface. Elevation contours are imaginary lines connecting points having the same elevation on the surface of the land above or below a reference surface, which is usually mean sea level. Contours make it possible to show the height and shape of mountains, the depths of the...
Where can I find indexes of USGS topographic maps?
View map indexes on these interactive maps (you must zoom in to see the index lines and map names) : Map Locator on the USGS Store - Click the icon on the left that looks like two pieces of paper and select “1:24,000” for our standard map series. TopoView - Click on any of the round map scale indicators on the right side of the map. The National Map Viewer - Click on the Layer List icon at the top...
How are UTM coordinates measured on USGS topographic maps?
The UTM ( Universal Transverse Mercator ) coordinate system divides the world into sixty north-south zones, each 6 degrees of longitude wide. UTM zones are numbered consecutively beginning with Zone 1, which includes the westernmost point of Alaska, and progress eastward to Zone 19, which includes Maine. If UTM ticks are shown on a USGS topographic map, the zone is indicated in the credit legend...
What is the State Plane Coordinate System? Can GPS provide coordinates in these values?
The State Plane Coordinate System (SPCS), which is only used in the United States, is a plane coordinate system (north-south and east-west lines are perpendicular) in which each individual state has between one to six zones, depending on the state's size and shape. This coordinate system’s high level of accuracy is achieved through the use of relatively small zones. The State Plane Coordinate...
What is declination?
At most places on the Earth's surface, the compass doesn't point exactly toward geographic north. The deviation of the compass from true north is an angle called "declination" (or "magnetic declination"). It is a quantity that has been a nuisance to navigators for centuries, especially since it varies with both geographic location and time . It might surprise you to know that at very high...
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- FAQ
How do I find, download, or order topographic maps?
The U.S. Geological Survey (USGS) has been the primary civilian mapping agency of the United States since 1879. Some of the most well-known USGS maps are the 1:24,000-scale topographic maps, also called 7.5-minute quadrangles . In 2009, the USGS transitioned from our hand scribed historical topographic maps to US Topos , which are computer-generated on a regular schedule using national databases...
Are USGS topographic maps copyrighted?
All topographic maps produced by the U.S. Geological Survey (USGS) are in the public domain and are not copyrighted except for the following three cases that apply only to US Topo maps (produced 2009-present): Most maps in the period 2010-2016 contain commercially licensed road data (see note below). Orthoimages in Alaska are commercially licensed. Orthoimages in Hawaii were commercially licensed...
Can I still get the older topographic maps?
Yes. Topographic maps originally published as paper documents between 1884-2006 have been scanned and published as the USGS Historical Topographic Map Collection . Download our historical topographic maps and our more current US Topo maps (published 2009-present) free of charge using TopoView (GeoPDF, GeoTIFF, JPEG, and KMZ formats) or using the USGS Store’s Map Locator (GeoPDF format). Order...
What is a topographic map?
The distinctive characteristic of a topographic map is the use of elevation contour lines to show the shape of the Earth's surface. Elevation contours are imaginary lines connecting points having the same elevation on the surface of the land above or below a reference surface, which is usually mean sea level. Contours make it possible to show the height and shape of mountains, the depths of the...
Where can I find indexes of USGS topographic maps?
View map indexes on these interactive maps (you must zoom in to see the index lines and map names) : Map Locator on the USGS Store - Click the icon on the left that looks like two pieces of paper and select “1:24,000” for our standard map series. TopoView - Click on any of the round map scale indicators on the right side of the map. The National Map Viewer - Click on the Layer List icon at the top...
How are UTM coordinates measured on USGS topographic maps?
The UTM ( Universal Transverse Mercator ) coordinate system divides the world into sixty north-south zones, each 6 degrees of longitude wide. UTM zones are numbered consecutively beginning with Zone 1, which includes the westernmost point of Alaska, and progress eastward to Zone 19, which includes Maine. If UTM ticks are shown on a USGS topographic map, the zone is indicated in the credit legend...
What is the State Plane Coordinate System? Can GPS provide coordinates in these values?
The State Plane Coordinate System (SPCS), which is only used in the United States, is a plane coordinate system (north-south and east-west lines are perpendicular) in which each individual state has between one to six zones, depending on the state's size and shape. This coordinate system’s high level of accuracy is achieved through the use of relatively small zones. The State Plane Coordinate...
What is declination?
At most places on the Earth's surface, the compass doesn't point exactly toward geographic north. The deviation of the compass from true north is an angle called "declination" (or "magnetic declination"). It is a quantity that has been a nuisance to navigators for centuries, especially since it varies with both geographic location and time . It might surprise you to know that at very high...
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