FAQ's about Topographic Maps

The University of New Hampshire has placed about 1,500 JPG-formatted images of historic topographic maps for New York and the New England states at http://docs.unh.edu/nhtopos/nhtopos.htm/.

Find more information about all USGS maps at the USGS Store and click on "Maps" in the left margin.

Most survey benchmarks were not established by the U.S. Geological Survey (USGS), but by the National Coast and Geodetic Survey, and are available on the web from http://www.ngs.noaa.gov ["Data sheets"]. For further assistance call 301-713-3242 or e-mail infocenter@ngs.noaa.gov.

USGS survey benchmark data is not yet available on the Internet

For Eastern U.S. vertical and horizontal control information contact USGS in Rolla, Missouri, by telephone 573-308-3500 or e-mail mcmcesic@usgs.gov.

For Western U.S. vertical and horizontal control information contact USGS in Denver, Colorado, by telephone 303-202-4400 or e-mail infoservices@usgs.gov.

There are several different sources available and dependent on the type of information you are searching for:

Digital Map Data

YES. Visit our Digital Geospatial Data Page or call 1-888-ASK-USGS for our information package on digital cartographic data.

Imagine walking along the beach. As you walk across the sand on the shore, your elevation stays constant. That path is drawn by one contour line. Now imagine walking from the shoreline into the ocean where the ground is below sea level. That path, which follows a different elevation than when you were walking on the shore, is drawn by a different contour line.

The distinctive characteristic of a topographic map is that the shape of the Earth's surface is shown by contour lines. These imaginary lines join points of equal elevation on the surface of the land above or below a reference surface such as mean sea level.

This can help measure depths of the ocean bottom, the height of mountains, and the steepness of slopes. But topographic maps show more than contours. These maps also include symbols that represent features such as streets, buildings, streams, and woods.

Scanned USGS topographic maps in GeoPDF format are available for download from the USGS Store.

Generally, for the conterminous United States, the North American Datum (NAD) shift amounts to about 210 meters. This shift occurs because of the change in shape of the spheroid used to define the datum. The GRS 80 spheroid (used for NAD 83) is shorter at the Equator and longer at the poles than the Clarke 1866 spheroid (which is used for NAD 27). The map collar says to move the projection just a few meters. The shift referenced in the map collar applies only to the LAT, LONG graticule on the map.

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'. 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 latitudes the compass can even point south! Declination is simply a manifestation of the complexity of the geomagnetic field. The field is not perfectly symmetrical, it has non-dipolar 'ingredients', and the dipole itself is not perfectly aligned with the rotational axis of the Earth. Interestingly, if you were to stand at the north geomagnetic pole, your compass, held horizontally as usual, would not have a preference to point in any particular direction, and the same would be true if you were standing at the south geomagnetic pole. Moreover, if you were to hold your compass on its side the north-pointing end of the compass would point down at the north geomagnetic pole, and it would point up at the south geomagnetic pole. Maps of declination, such as that shown below (contours of 10 degrees east), as well as other field components, and a program for determining the magnetic field at any geographic location, are given in the Models, Charts, and Movies pages of this website.

USGS Field Records Library

Box 25046, MS 914

Denver Federal Center

Denver, CO 80225-0046

Telephone: 303-236-1000

FAX: 303-236-0015

TDD: 303-236-0998

E-mail: den_lib@usgs.gov

Jill Schneider

USGS Mineral Resources Surveys

Alaska Section

4200 University Drive

Anchorage, AK 99508-4667

Telephone: 907-786-7457 (Office) and 907-786-7007 (Library)

FAX: 907-786-7401

E-mail: jschnidr@usgs.gov

Two other sources of field records are:

1. National Archives and Records Administration (NARA) in College Park, Maryland, which keeps field record materials in their Archives II facility. Refer to the Guide to Federal Records in the National Archives of the United States (Washington, D.C.: NARA, 1995).

Inventory of the Records of the United States Geological Survey, Record Group 57, in the National Archives, part of USGS Circular 1179 (2000, CD-ROM): Records and History of the United States Geological Survey, contains information on USGS and related records accessioned by NARA through 1997 and held at NARA-II. Appendices in this inventory list field records held at NARA-II and by the USGS Field Records Library at Denver.

National Archives and Records Administration

8601 Adelphi Road

College Park, MD 20740-6001

Telephone: 301-713-6800 (General Reference Information)

Telephone: 1-866-272-6272 (Toll Free)

E-mail: inquire@nara.gov

URL: http://www.archives.gov/index.html

The Smithsonian Institution Archives

Arts and Industries Building, Room 2135

900 Jefferson Drive, S.W.

Washington, D.C. 20560

Telephone: 202-357-1420

E-mail: OSIAREF@OSIA.SI.EDU

Rocky Mountain Mapping Center

USGS National Mapping Division

Box 25046, MS 506, Federal Center

Denver, CO 80225-0046

Telephone: 303-202-4394

Mid-Continent Mapping Center

USGS National Mapping Division

MS 309

1400 Independence Road

Rolla, MO 65401

Telephone: 573-308-3663

The distances vary. A degree, minute or second of latitude remains fairly constant from the equator to the poles; however a degree, minute, or second of longitude can vary greatly as one approaches the poles (because of the convergence of the meridians). At 38 degrees North latitude, one degree of latitude equals approximately 364,000 ft (69 miles), one minute equals 6068 ft (1.15 miles), one-second equals 101 ft; one-degree of longitude equals 288,200 ft (54.6 miles), one minute equals 4800 ft (0.91 mile), and one second equals 80 ft.

The cost of USGS maps covers the expense of printing and distribution only. Tax dollars pay for the costs associated with information collection, analysis, production, and archiving.

A DRG is a scanned image of a U.S. Geological Survey (USGS) topographic map. The scanned image includes all map collar information. The image inside the map neatline is georeferenced to the surface of the Earth.

DRG Fact Sheet

Topographic maps published by the U.S. Geological Survey generally are named for the most centrally located and/or well-known or largest community named on the map. Note that the largest, most well known community may not be centrally located. The name may be scale dependent, that is, the smaller the scale, the larger the area shown, and therefore, the more named features available to be selected for the map name.

To the extent possible, names are selected for communities that are wholly located within the map. If the community for which the map should be named falls on two or more maps, a directional term might be used such as East and West. An example is Washington East and Washington West, D.C.

If the map contains no communities or they are very rural, small, and scattered, it can be named for the most, prominent and centrally located well-known physical or natural feature such as a mountain. As with communities, the feature should be wholly located on the map.

Naming maps for linear features such as streams is generally avoided because such features usually pass through maps or meander on and off the maps. Occasionally, a map area is so devoid of named topography that a directional might be used, as in adding NW or SE to the name of an adjacent map, or even using the map name from a smaller scale series and applying the directional term.

The State Plane Coordinate System (SPCS) is a plane coordinate system (N-S and E-W lines are perpendicular) in which each individual state has from one to six zones, depending on the state's size and shape. The grid system in some states is based on the Lambert Conformal Conic Projection, while the system for other states is based on the Transverse Mercator Projection. As a general rule-of-thumb, states that are longer E-W than N-S use Lambert, while states that are longer N-S use Transverse Mercator. The most notable exception to this is California, which is based on Lambert.

For NAD27, all coordinates were based on U. S. Survey Feet. USGS 7.5' maps show 10,000 foot black grid ticks along the perimeter of the map. The appropriate zone is listed in the margin data at the lower left-hand corner of the map.

For NAD83, coordinates may be in meters, U. S. Survey Feet, or International Feet depending on the State. Each State was allowed to choose which unit of measure they wanted for surveys within their boundaries. Some states changed origins for their State Plane Coordinate System when switching from NAD27 to NAD83. For these reasons, using this grid system has become less popular than in the past.

Some Trimble professional grade GPS receivers are capable of providing positions in the State Plane Coordinate System. Of course, latitude/longitude or UTM positions recorded in the field or post processed in a computer, can be transformed to SPCS through computer software.

GPS cannot provide readouts in the Public Land Survey System (PLSS). Points can be plotted onto a map in lat/long or UTM. From that position a user can determine the Section that encompasses the point.

Once you've gathered as many facts about family history and customs as possible, turn to maps to uncover more specific information or to solve historical "mysteries."

Old and new maps can help you track down facts about a branch of your family. How? In the United States, birth, death, property, and some other kinds of records are normally kept by the county governments. If you can name the place where an ancestor lived, new or old maps of that place may also show the county seat where useful data about your kin can be obtained.

Old maps can be particularly useful in this regard because pinpointing the name of the place where an ancestor lived can be like trying to hit a moving target. Many towns, counties, cities, and even countries have experienced numerous name changes over the years.

Though their names have changed, some of these places may be noted on an old map. The location of some others may be found in sources such as lists of abandoned post offices, local histories, government records, microfilm records, or clippings from old newspapers, old city directories, or old county atlases kept in the library archives of a town, city, or county in the region.

You may view, download, and order topographic maps directly from the USGS Store on-line.  The following instructions will help you to find the maps you desire.

First go to the USGS Store on-line: http://store.usgs.gov

Once at this site, located within the brown, left-column of the page, select "Map Locator".  A map of the United States will open and located on the right side is a search box.  Enter "Your Location" within the search box, and below this box, select search type "Address or Place" (you may also search by map name).  The map of the United States will zoom into the topographic quadrangle map for that location.  You may zoom out to show all adjacent maps, or use your cursor to move the view of the map around (however, zooming in or out too far will take away the map name display grid). 

Below the map is a large yellow bar "Show DigMaps - Beta".  Click on this bar and an index grid will overlay on the map.  The DigMaps - Beta are part of a project to update the USGS topographic maps.  They are orthoimages of the 7.5 minute quadrangles with information layers applied to them.  Currently the project completion is sporadic, with files showing primarily roads and geographic names.  In the near future they will include hydrology and contours as well as cover the entire United States.

A red marker will also appear on the map.  Left-click on the red marker and a box will open listing the names of all scales of maps available for that particular area.  This box also includes a direct link to the digital geoPDF file and the digital map beta file, both of which you can download directly to your computer, as well as to the shopping cart of the store in which you can purchase these maps from the website.  You may place additional markers on any area of interest, left-click and view the maps that are available for any marked location.

These maps are the most current publications available.  You may contact the USGS for help locating and ordering historic maps. 

If you have questions, need help with the on-line ordering process, or would like to speak with a USGS representative, please call 1-888-ASK-USGS (1-888-275-8747).

We generally emphasize the following four points:

a) Select a coordinate system. We usually suggest using either the Universal Transverse Mercator System (UTM) or latitude/longitude. Using UTM results in easier plotting on the USGS 7.5' quadrangle maps. The coordinate system displayed by your GPS is usually just a position format selection on your unit's navigation set up page.

b) Select the correct horizontal datum. Most GPS units default to a datum called the World Geodetic System of 1984 (WGS84). However, most USGS maps are referenced to a different datum, the North American Datum of 1927 (NAD27). A few USGS maps are set to the North American Datum of 1983 (NAD83), which is virtually identical to WGS84. Check the map information at the lower left corner of the USGS 7.5' quadrangle to determine the correct datum used in the making of the map. Correct datum is especially important of you are using the UTM coordinate system. Your GPS setup menu may present several variations of NAD27 to select from; most users will select NAD27 CONUS, which is appropriate for the continental US.

c) Be aware that the vertical heights displayed by your recreational GPS receiver will not agree well with USGS map elevations. The main reasons for this discrepancy is the inherent poor fix geometry available for vertical determinations (the earth is always blocking some of the desired satellites) and the use of different reference surfaces for the vertical measurement. DO NOT USE GPS ELEVATIONS FOR CRITICAL NAVIGATION DECISIONS.

d) Select which "North" your GPS receiver will use as the zero degree reference. The default in your receiver is probably true north = 0 degrees. You can also select magnetic north = 0 degrees or grid north (north-south lines of the UTM grid) = 0 degrees. Many users select magnetic north as zero degrees so they can follow a compass bearing without converting the azimuth to true north. Many GPS units automatically calculate the local magnetic variation (declination) for the fixed time and date.

UTM is the acronym for Universal Transverse Mercator, a plane coordinate grid system named for the map projection on which it is based (Transverse Mercator). The UTM system consists of 60 zones, each 6-degrees of longitude in width. The zones are numbered 1-60, beginning at 180-degrees longitude and increasing to the east. The military uses their own implementation of the UTM system, called the Military Grid Reference System (MGRS).

UTM coordinates are measured on the map by subdividing the 1000 meter grid squares into tenths or hundredths. This will narrow down the coordinate to a 100 or 10 meter square. Usually the measurements are made using a simple mylar or paper scale or a coordinate reader. Note that the large numbers that are located adjacent to the tick marks around the perimeter of the map represent tens of thousand and thousands of meters. The millions and hundreds of thousands of meters are shown with small numbers and are sometimes dropped when giving UTM coordinate positions. The military implementation of UTM (MGRS) drops the small digits and indicates the 100,000 meter square by a two letter identifier. Most UTM users and GPS units use the full value of the UTM coordinates.

If coordinates are to be passed on to another person it is technically necessary to report the horizontal datum and the latitude/longitude of the point (e.g. NAD 27 CONUS, 44 degrees, 7 minutes, 30 seconds north/ 104 degrees, 15 minutes, 10 seconds west). If using UTM, include datum, grid zone number, row indicator, easting and then the northing value (e.g. NAD 83/13 S/ 0404524E/ 4239242N). UTM coordinates are always read to the right and up. Different needs may dictate different reporting schemes.