Topographic map

(mapping) A large-scale map showing relief and man-made features of a portion of a land surface distinguished by portrayal of position, relation, size, shape, and elevation of the features.

Background

A topographic map is a two-dimensional representation of a three-dimensional land surface. Topographic maps are differentiated from other maps in that they show both the horizontal and vertical positions of the terrain. Through a combination of contour lines, colors, symbols, labels, and other graphical representations, topographic maps portray the shapes and locations of mountains, forests, rivers, lakes, cities, roads, bridges, and many other natural and man-made features. They also contain valuable reference information for surveyors and map makers, including bench marks, base lines and meridians, and magnetic declinations. Topographic maps are used by civil engineers, environmental managers, and urban planners, as well as by outdoor enthusiasts, emergency services agencies, and historians.

History

Some of the earliest known maps were made in Mesopotamnia, in the area now known as Iraq, where a series of maps showing property boundaries were drawn in about 2400 B.C. for the purpose of land taxation. A Roman map dating from about 335-366 A.D. showed such topographical features as roads, cities, rivers, and mountains. The word topography is derived from the Greek words topos, meaning a place, and graphien, meaning to write. Thus, topography is the written, or drawn, description of a place.

Although the basics of land surveying were known as early as 1200 B.C., and perhaps even earlier, the use of surveying techniques in preparing maps was limited to cities and other small-scale areas. Larger-scale maps were prepared from sketches or journals kept by explorers and sometimes reflected more imagination than observation. As a result, the exact positions of points on a map were often grossly in error.

In 1539, the Dutch mathematician and geographer Reiner Gemma Frisius described a method for surveying an area by dividing it into triangles. This concept of triangulation became one of the basic techniques of field surveying and is still used today. One of the first large-scale mapping projects using triangulation was started in the 1670s by Giovanni Domenico Cassini, who had been persuaded to make a detailed map of France. After Cassini's death, his children and grandchildren continued to labor on the project. The final result, called the Carte de Cassini, was published in 1793 and was the first accurate topographic map of an entire country. Its only shortcoming was the general lack of elevation measurements, other than a few spot elevations determined by measuring the variation in air pressure with altitude using a barometer. The concept of contour lines to show different elevations on a map was developed by the French engineer J.L. Dupain-Triel in 1791. Although this method allowed the accurate depiction of land contours and elevations on a flat, two-dimensional map, it was not widely used until the mid-1800s.

In the United States, the federal government recognized the importance of accurate topographic maps in a rapidly growing country. In 1807, President Thomas Jefferson established the Survey of the Coast to map the Atlantic coastline as an aid to travel and commerce. In 1836, this organization was renamed the U.S. Coast Survey, and in 1878 the name changed to the U.S. Coast and Geodetic Survey. In the meantime, mapping of the interior of the country fell to a variety of individuals and organizations, including the Lewis and Clark expedition in 1804-1806, who mapped their route from St. Louis, Missouri, to the Pacific Northwest. During the period from 1838 until the outbreak of the Civil War in 1861, the Army's Corps of Topographical Engineers made major contributions in mapping the western United States, including a detailed map published in 1848 based on John Fremont's explorations. By the 1870s, so many different groups were conducting surveys that their work began to overlap. To consolidate this effort, the U.S. Geological Survey (USGS) was established in 1879.

Most of the early map making was done by laborious field surveys. Starting in the 1930s, the USGS began using aerial photography techniques to produce and update maps. In the 1980s the use of computers to scan and redraw existing maps significantly reduced the time required to update maps in areas of rapid growth.

Today, the USGS has more than 56,000 topographic maps of the United States in various scales, plus maps of the moon and planets. They also publish specialty maps including geologic, hydrologic, and photoimage maps for a variety of uses.

Map Scales, Symbols,
and Colors

In order to be useful, topographic maps must show sufficient information on a map size that is convenient to use. This is accomplished by selecting a map scale that is neither too large nor too small and by enhancing the map details through the use of symbols and colors.

The most common USGS topographic map scale is 1:24,000. In this scale 1 inch on the map represents 24,000 in, or 2,000 ft. (1 cm represents 240 m) on the ground. These maps are called 7.5 minute quadrangle maps because each map covers a four-sided area on the surface of Earth that is 7.5 minutes of longitude wide and 7.5 minutes of latitude high, where 60 minutes equals one degree of angle. Because the distance between longitude lines gets narrower as you move from the equator towards the poles, the widths of the maps also vary. For maps of the United States, the maps measure about 23 in (58.4 cm) wide by 27 in (68.6 cm) high for locations below a latitude of 31 degrees and about 22 in (55.9 cm) wide by 27 in (68.6 cm high) for locations above that latitude. Other common USGS map scales are 1:63,360, 1:100,000, and 1:250,000. These scales cover larger areas than the 1:24,000 maps, but with less detail.

In order to make the topographic maps easier to interpret, symbols and colors are used to represent various natural and man-made features. Some symbols are designed to look like the feature when viewed from overhead. For example, buildings are shown as solid objects in the shape of the building outline. Other symbols are universally recognized representations such as a long line with small cross marks to represent a railroad. Colors play an even more important role. Rivers, lakes, and other bodies of water are shown in blue. Forests and heavily vegetated areas are shown in green. Minor roads and highways are shown in black, while major highways are shown in red. Contour lines, which represent the shape of the ground itself, are shown in brown. Recent revisions to the map are shown in purple.

The Manufacturing
Process

The production of an accurate topographic map is a long and complex process that may take as much as five years from start to finish. It takes a skilled team of surveyors, engravers, fact checkers, printers, and others to produce a good map. Here is a typical sequence of operations used by the U.S. Geological Survey to produce a 7.5 minute quadrangle topographic map.

Photographing the area

• The area to be mapped must first be photographed from the air. Each section of ground is photographed from two different angles to provide a stereoscopic three-dimensional image that can be converted into contour lines. The sky must be clear, and the sun must be at the proper angle for the type of terrain being photographed. Seasonal factors must also be taken into consideration. For example, in areas where there are deciduous trees, the photos are usually taken between late fall and early spring when the trees are bare and the underlying ground features are more visible.
• The aircraft is flown over the area at a constant altitude in a north-south direction along carefully determined flight paths while special cameras take 10 precisely positioned photographs of each quadrangle. Each camera can cost $250,000 or more.

Surveying the control points

• To ensure the accuracy of a map, the exact location of various control points must be established by field surveys. Typical control points may be the intersection of two roads or other prominent features within the map area. Horizontal control points are surveyed to determine the longitude and latitude, while vertical control points are surveyed separately to determine elevations. The location and elevation of these control points help the map makers correctly position the aerial photo images and assign values to the contour lines.
• While the surveyors are in the field, they also look for features, which may require further checking, such as roads or streams hidden beneath overhanging foliage, or buildings that may have been constructed or demolished since the aerial photographs were taken.

Verifying the map features

• Some map features may require additional verification. For example, some streams may run only intermittently, in which case they would be represented on the map by a dash-dot or lighter-weight instead of a solid line. Certain roads may turn out to be private roads, rather than public roads, and these must be marked. Field checkers go into the area and verify these features by talking with local residents or consulting local property records. Any questionable features noted by the survey crews must also be verified. The correct spelling of place names must be determined.

Compiling the map manuscript

• After the area has been surveyed and all the features have been checked, the pairs of overlapping aerial photographs are placed in a stereoscopic projector. One image is projected to the operator's left eye and the other image to his right eye. The result is a three-dimensional view of the terrain. Two small beams of light are connected to a pointer and are adjusted to intersect in a tiny white dot corresponding to a given elevation on the three-dimensional terrain image. By moving the pointer while keeping the two beams focused in a dot, the operator traces each contour line of the ground and the location of various features. The pointer is connected to a pen on the tracing table that draws the contour or feature being traced. All contours and features are drawn in black at this point. This process is called compiling the map manuscript.
• When the tracing is completed, the finished map manuscript is photographed, and a map-sized film negative is made. This negative is photochemically reproduced onto several thin plastic sheets coated with a soft, translucent coating called a scribecoat.

Scribing and editing the map

• The plastic sheets are taken one at a time and placed on a light table, where a soft light shines up through a white plastic surface. This illumination from below makes the lines of the map manuscript visible through the scribecoat. An engraver carefully cuts away the scribecoat along the lines and areas that are to be a certain color on the finished map. For example, one sheet will have all the lines for rivers, lakes, and other bodies of water that are to be blue. This process is repeated for each color.
• Separate sheets for the lettering are prepared by placing a clear plastic sheet over each scribed sheet and carefully aligning the lettering with the features to be labeled. Type sizes, styles, and fonts are selected according to standards, which assure consistency and legibility from one map to another. A film negative is then made of each finished type sheet.
• After the scribed sheets are reviewed and edited several times, a color proof sheet is made by exposing each sheet under different color light to produce a color print that looks very much like the finished map. After further review and editing, the map is ready to be printed.

Printing the map

• A press plate is prepared for each map color by exposing the scribed sheets and the lettering negatives. Paper is loaded into a lithographic printing press, and the first color is printed. The press plate and ink are changed and the paper is run through the press a second time to print the second color. This process is repeated until all the colors have been printed. Some of the largest presses can print up to five colors in sequence without changing plates or reloading the paper.

Quality Control

The USGS uses the National Map Accuracy Standards set up in 1947. Starting in 1958, the USGS began testing the accuracy of their maps by field checking 20 or more well defined points on about 10% of the maps being produced each year.

For a 7.5 minute map at 1:24,000 scale, the horizontal accuracy standard requires that the locations shown on the map for at least 90% of the points checked must be accurate to within 40 ft (12.2 m) of the actual locations on the ground. The vertical accuracy standard requires that the elevations shown on the map for at least 90% of the points checked must be accurate to within one half of the contour interval on the ground. For a map with 10 ft (3 m) contour intervals, this means the elevations shown on the map must be accurate to within 5 ft (1.5 m) of the actual elevations on the ground. To give you an idea of what these standards mean to map makers, the horizontal accuracy standard requires that the location of at least 90% of the check points on the map must be drawn to within 0.02 in (0.05 cm) of the correct position.

The Future

Most of the topographic maps currently in use were produced manually. For mapmakers, however, the future is here today. A well-established network of navigational satellites form the basis of the Global Positioning System (GPS). This system allows field surveyors to accurately determine horizontal positions within a few feet, even in the most remote terrain where conventional surveying techniques are impossible.

Other satellites carrying a variety of sensors may soon replace the aerial photography method of making maps. The first of a series of Landsat satellites was launched in 1972, and by 1984 they could detect objects on the surface of Earth about 100 ft (30 m) in size. In 1998, an American company was preparing to launch a satellite that could detect objects as small as 3 ft (1 m), which would produce images with as much detail as current USGS 7.5 minute maps. More importantly, these images would be captured and transmitted as digital data, which could then be processed and printed by computers. This would significantly reduce the time required to produce or update maps and would improve the overall accuracy as well.

Where to Learn More

Books

Thompson, Morris M. Maps for America, 3rd edition. U.S. Department of the Interior, Geological Survey National Center, 1987.

Periodicals

Pike, Richard J. and Gail P. Thelin. "Building a Better Map." Earth (January 1992): 44-51.

Wilford, John Noble. "Revolutions in Mapping." National Geographic (February 1998): 6-39.

Other

"Map Accuracy Standards." U.S. Department of the Interior, U.S. Geological Survey, July 1996.

"Map Scales." U.S. Department of the Interior, U.S. Geological Survey, October 1993.

"Topographic Mapping." U.S. Department of the Interior, U.S. Geological Survey.

"Topographic Map Symbols." U.S. Department of the Interior, U.S. Geological Survey.

U.S. Geological Survey. http://www.usgs.gov.

[Article by: Chris Cavette]

(Data West Research Agency definition: see GIS glossary.) A map depicting terrain relief showing ground elevation, usually through either contour lines or spot elevations. The map represents the horizontal and vertical positions of the features represented. It is a graphic representation delineating natural and man-made features of an area or region in a way that shows their relative positions and elevations.

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A map that presents the vertical position of features in measurable form as well as their horizontal positions.

See the Introduction, Abbreviations and Pronunciation for further details.

A map which indicates, to scale, the natural features of the earth's surface, as well as human features. The features are shown at the correct relationship to each other.

A map reflecting the shape, or topography, of Earth's surface. Topography can be depicted using contour lines of equal elevation or by using shading techniques to simulate a three dimensional surface.

(DOD) A map that presents the vertical position of features in measurable form as well as their horizontal positions. See also map.

A topographic map with contour lines

Part of the same map in a perspective shaded relief view illustrating how the contour lines follow the terrain Section of topographical map of Nablus area (West Bank) with contour lines at 100-meter intervals. Heights are colour-coded

Topographic map of India. Color scale of altitude is shown.

A topographic map is a type of map characterized by large-scale detail and quantitative representation of relief, usually using contour lines in modern mapping, but historically using a variety of methods. Traditional definitions require a topographic map to show both natural and man-made features.

The Canadian Centre for Topographic Information provides this definition of a topographic map:^[1]

A topographic map is a detailed and accurate graphic representation of cultural and natural features on the ground.

Other authors define topographic maps by contrasting them with another type of map; they are distinguished from smaller-scale "chorographic maps" that cover large regions,^[2][3] "planimetric maps" that do not show elevations,^[4] and "thematic maps" that focus on specific topics.^[5]

However, in the vernacular and day to day world, the representation of relief (contours) is popularly held to define the genre, such that even small-scale maps showing relief are commonly (and erroneously, in the technical sense) called "topographic".^[3]

The study or discipline of topography, while interested in relief, is actually a much broader field of study which takes into account all natural and man made features of terrain.

Contents 1 History 2 Uses 3 Map conventions 4 Publishers of national topographic map series 4.1 Australia 4.2 Canada 4.3 Denmark 4.4 Finland 4.5 France 4.6 Germany 4.7 Greece 4.8 India 4.9 Japan 4.10 New Zealand 4.11 Switzerland 4.12 United Kingdom 4.13 United States 5 See also 6 References 7 External links

History

Topographic maps are based on topographical surveys. Performed at large scales, these surveys are called topographical in the old sense of topography, showing a variety of elevations and landforms.^[6] This is in contrast to older cadastral surveys, which primarily show property and governmental boundaries. The first multi-sheet topographic map series of an entire country, the Carte géométrique de la France, was completed in 1789.^[7] Topographic surveys were prepared by the military to assist in planning for battle and for defensive emplacements (thus the name and history of the United Kingdom's Ordnance Survey). As such, elevation information was of vital importance.^[8]

As they evolved, topographic map series became a national resource in modern nations in planning infrastructure and resource exploitation. In the United States, the national map-making function which had been shared by both the Army Corps of Engineers and the Department of the Interior migrated to the newly created United States Geological Survey in 1879, where it has remained since.^{[9] [10]}

Uses

Topographic maps have multiple uses in the present day: any type of geographic planning or large-scale architecture; earth sciences and many other geographic disciplines; mining and other earth-based endeavours; and recreational uses such as hiking or, in particular, orienteering, which uses highly detailed maps in its standard requirements.

Map conventions

For more about contour lines, see Cartographic relief depiction.

The various features shown on the map are represented by conventional signs or symbols. For example, colors can be used to indicate a classification of roads. These signs are usually explained in the margin of the map, or on a separately published characteristic sheet.^[11]

Topographic maps are also commonly called contour maps or topo maps. In the United States, where the primary national series is organized by a strict 7.5 minute grid, they are often called topo quads or quadrangles.

Topographic maps conventionally show topography, or land contours, by means of contour lines. Contour lines are curves that connect contiguous points of the same altitude (isohypse). In other words, every point on the marked line of 100 m elevation is 100 m above mean sea level.

These maps usually show not only the contours, but also any significant streams or other bodies of water, forest cover, built-up areas or individual buildings (depending on scale), and other features and points of interest.

Today, topographic maps are prepared using photogrammetric interpretation of aerial photography, LIDAR and other Remote sensing techniques. Older topographic maps were prepared using traditional surveying instruments.

Publishers of national topographic map series

Most countries have some sort of national mapping program. Those listed below are only a small selection. Several commercial vendors supply international topographic map sets.

Australia

The National Mapping Information Group of Geoscience Australia is the Australian Government's national mapping agency. It provides topographic maps and data to meet the needs of the sustainable development of the nation. The Office of Spatial Data Management provides an online free map service MapConnect[2]^[12]. These topographic maps of scales 1:250,000 and 1:100,000 are available in printed form from the Sales Centre^[13]. 1:50,000 and 1:25,000 maps are produced in conjunction with the Department of Defence^[14] .

Canada

The Centre for Topographic Information produces topographic maps of Canada at scales of 1:50,000 and 1:250,000. They are known as the National Topographic System (NTS).^[15] A government proposal to discontinue publishing of all hardcopy or paper topographic maps in favor of digital-only mapping data was shelved in 2006 after intense public opposition.^[16]

Denmark

The National Survey and Cadastre of Denmark is responsible for producing topographic and nautical geodata of Denmark, Greenland and the Faroe Islands.^[17]

Finland

The National Land Survey of Finland produces the Topographic Database (accuracy 1:5000-1:10 000) and publishes topographic maps of Finland at 1:25,000 and 1:50,000. In addition topographics maps can be viewed by using a free map service MapSite[3]^[18]

France

The Institut Géographique National (IGN) produces topographic maps of France at 1:25,000 and 1:50,000.^[19] In addition, topographic maps are freely accessible online, through the Géoportail website.

Germany

In principle, each federal state (Bundesland) is in charge of producing the official topographic maps. In fact, the maps between 1:5,000 and 1:100,000 are produced and published by the land surveying offices of each federal state, the maps between 1:200,000 and 1:1,000,000 by a federal office - the Bundesamt für Kartographie und Geodäsie (BKG) in Frankfurt am Main.

Greece

Topographic maps for general use are available at 1:50,000 and 1:100,000 from the Hellenic Military Geographical Service (HMGS) [4]. They use a national projection system called EGSA'87, which is a Transverse Mercatorial Projection mapping Greece in one zone. A few areas are also available at 1:25,000. Some private firms sell topographic maps of national parks based on HMGS topography.

India

The Survey of India is responsible for all topographic control, surveys and mapping of India.^[20]

Japan

The Geographical Survey Institute of Japan is responsible for base mapping of Japan. Standard map scales are 1:25,000, 1:50,000, 1:200,000 and 1:500,000 ^[21]

New Zealand

Land Information New Zealand is the government agency responsible for providing up-to-date topographic mapping. LINZ topographic maps cover all of New Zealand, offshore islands, some Pacific Islands and the Ross Sea Region.^[22] Vector data [5] from the New Zealand Topographic Database (NZTopo) is also available. NZTopoOnline is a publicly accessible, free online service.^[23]

Switzerland

Swisstopo (the Federal Office of Topography) produces topographic maps of Switzerland at seven different scales.

United Kingdom

The Ordnance Survey (OS) produces topographic map series covering the United Kingdom at 1:25,000 and 1:50,000 scales. The 1:25,000 scale is known as the "Explorer" series, and include an "OL" (Outdoor Leisure) sub-series for areas of special interest to hikers and walkers. It replaced the "Pathfinder" series, which was less colourful and covered a smaller area on each map. The 1:50,000 scale is known as the "Landranger" and carries a distinctive pink cover. More detailed mapping as fine as 1:10000 cover some parts of the country.^[24] The 1:25K and 1:50K metric scales are easily coordinated with standard romer scales on currently available compasses and plotting tools. The Ordnance Survey maintains a mapping database from which they can print specialist maps at virtually any scale.^[25]

United States

The United States Geological Survey (USGS), a civilian Federal agency, produces several national series of topographic maps which vary in 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, 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 minutes apart. Nearly 57,000 individual maps in this series cover the 48 contiguous states, Hawaii, 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 64 square miles (166 km²). At 49° north latitude, 49 square miles (127 km²) 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.^[26] 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^[27] (not to be confused with the National Atlas of the United States produced by the 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, but was discontinued some time ago for maps covering the continental U.S. Each map was bounded by two parallels and two 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.^[26] The U.S.A. 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 U.S., though only for use by members of its defense forces).

The next-smallest topographic series, in terms of scale, is the 1:100,000 series. These maps are bounded by two lines of longitude and two lines of latitude. However, in this series, the lines of latitude are spaced 30 minutes apart and the lines of longitude are spaced 60 minutes, which is the source of another name for these maps; the 30 x 60-minute quadrangle series. Each of these quadrangles covers the area contained within 32 maps in the 7.5-minute series. The 1:100,000 scale series is unusual in that it employs the Metric system primarily. One centimeter on the map represents one kilometer of distance on the ground. Contour intervals, spot elevations, and horizontal distances are also specified in meters.

The final regular quadrangle series produced by the USGS is the 1:250,000 scale topographic series. Each of these quadrangles in the conterminous United States measures 1 degree of latitude by 2 degrees of longitude. This series was produced by the U.S. Army Map Service in the 1950s, prior to the maps in the larger-scale series, and consists of 489 sheets, each covering an area ranging from 8,218 square miles (21,285 km²) at 30° north to 6,222 square miles (16,115 km²) at 49° north.^[26] Hawaii is mapped at this scale in quadrangles measuring 1° by 1°.

USGS topographic quadrangle maps are marked with grid lines and tics around the map collar which make it possible to identify locations on the map by several methods, including the graticule measurements of longitude and latitude, the township and section method within the Public Land Survey System, and cartesian coordinates in both the State Plane Coordinate System and the Universal Transverse Mercator coordinate system.

Other specialty maps have been produced by the USGS at a variety of scales. These include county maps, maps of special interest areas, such as the national parks, and areas of scientific interest.

A number of Internet sites have made these maps available on the web for affordable commercial and professional use. Because works of the U.S. Government are in the public domain, it is also possible to find many of these maps for free at various locations on the Internet. Georeferenced map images are available from the USGS as digital raster graphics (DRGs) in addition to digital data sets based on USGS maps, notably Digital Line Graphs (DLGs) and digital elevation models (DEMs).

See also

• Bathymetric chart
• Hypsometric tints
• Topographic profile
• Raised-relief map

References

1. ^ Centre for Topopgraphic Information, Topo Maps: Frequently Asked Questions
2. ^ P. D. A. Harvey, The History of Topographical Maps: Symbols, Pictures and Surveys, Thames and Hudson, 1980, ISBN 0-500-24105-8, p. 9. "By a topographical map, we mean a large-scale map, one that sets out to convey the shape and pattern of landscape, showing a tiny portion of the earth's surface as it lies within one's own direct experience, and quite distinct from the small-scale maps that show us the features of whole provinces, nations and continents."
3. ^ ^{a b} Art & Architecture Thesaurus entry for topographic maps.
4. ^ Committee on Nomenclature of the American Society of Photogrammetry, "Definitions of terms used in photogrammetric surveying and mapping: preliminary report", Photogrammetric Engineering, 8, 247-283, 1942. "Topographic Map. A map that presents the horizontal and vertical positions of the features represented; distinguished from a planimetric map by the addition of relief in measurable form." This definition is used in many glossaries of map terminology.
5. ^ M.-J. Kraak and F. Ormeling, Cartography: Visualization of Spatial Data, Longman, 1996, ISBN 0-582-25953-3, p. 44. "Traditionally, the main division of maps is into topographic and thematic maps. Topographic maps supply a general image of the earth's surface: roads, rivers, buildings, often the nature of the vegetation, the relief and the names of the various mapped objects."
6. ^ The range of information is indicated by the title of a map produced in 1766: A Topographical Map of Hartfordshire from an Actual Survey in which is Express'd all the Roads, Lanes, Churches, Noblemen and Gentlemen's Seats, and every Thing remarkable in the County, by Andrew Dury and John Andrews, reprinted by Hertfordshire Publications in 1980. This showed the relief by using hachures.
7. ^ Library of Congress, Geography and Maps: General Collections
8. ^ Peter Barber, The Map Book, Weidenfeld & Nicolson, 2005, ISBN 0-297-84372-9, pp. 232, 250.
9. ^ "Organizing the U.S. Geological Survey". The United States Geological Survey: 1879-1989. U.S. Geological Survey, U.S. Department of the Interior. 2000-04-10. http://pubs.usgs.gov/circ/c1050/organize.htm. Retrieved 2007-06-19. 
10. ^ "The Four Great Surveys of the West". The United States Geological Survey: 1879-1989. U.S. Geological Survey, U.S. Department of the Interior. 2000-04-10. http://pubs.usgs.gov/circ/c1050/surveys.htm. Retrieved 2007-06-19. 
11. ^ Ordnance Survey, Explorer Map Symbols; Swisstopo, Conventional Signs; United States Geological Survey, Topographic Map Symbols.
12. ^ Geoscience Australia MapConnect
13. ^ Geoscience Australia Sales Centre
14. ^ DIGO
15. ^ Centre for Topographic Information website.
16. ^ Canada shreds plan to scrap paper maps
17. ^ Kort & Matrikelstyrelsens website (in Danish).
18. ^ National Land Survey of Finland.
19. ^ Institut Géographique National website (in French, English and German).
20. ^ Department of Scientific and Technology: Survey of India
21. ^ Omni Resources catalog page
22. ^ Land Information New Zealand.
23. ^ [1]
24. ^ 1:10 000 Scale Raster: mid-scale high-resolution detailed mapping
25. ^ Ordnance Survey website. The MasterMap Topography Layer contains information about buildings, roads, woodland, administrative boundaries, etc, with just a few spot heights along the roads. For contours or a digital terrain model, a separate product called Land-Form Profile is required.
26. ^ ^{a b c} USGS Topographic Maps and "USGS Maps Booklet". http://erg.usgs.gov/isb/pubs/booklets/usgsmaps/usgsmaps.html. 
27. ^ "The U.S. Geological Survey's Revision Program for 7.5-Minute Topographic Maps", Larry Moore (USGS), December, 2000.

External links

Atlas portal

• Topographic Symbols - U.S. military guide to topographic maps (use "Index" on the right hand side to navigate around the website)
• How a Topographic Map is Manufactured, History, and Other Information
• Digital topographic map library
• 1:50,000 Scale Romer for Download
• National Geographic's TOPO! Explorer Website Seamless USGS topographic maps for the US.
• US/New England topo map - New England topographic maps for GPS.

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