Topographic 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

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. A topographic map is typically published as a map series, made up of two or more map sheets that combine to form the whole map.

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 South Africa 4.12 Switzerland 4.13 United Kingdom 4.14 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

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 series.

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]

South Africa

The Chief Directorate: National Geo-spatial Information (CD:NGI) is responsible for the official, definitive, national topographic mapping and control network system of South Africa. The CD:NGI provides a range of maps, aerial photography, survey services and computer data products for government departments, commerce, planning, administrative, educational, management and leisure use.^[24]

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.^[25] 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.^[26]

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.

See also

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

References

External links

• 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

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