Topographic map
In modern mapping, atopographic maportopographic sheetis a type ofmapcharacterized by large-scaledetail and quantitative representation of relief features, usually usingcontour lines(connecting points of equal elevation), but historically using avariety of methods.Traditional definitions require a topographic map to show both natural and artificial features.[1]A topographic survey is typically based upon a systematic observation and published as amap series,made up of two or more map sheets that combine to form the whole map. A topographic map series uses a common specification that includes the range of cartographic symbols employed, as well as a standard geodetic framework that defines themap projection,coordinate system,ellipsoidandgeodetic datum.Official topographic maps also adopt a national grid referencing system.
Natural Resources Canadaprovides this description of topographic maps:[2]
These maps depict in detail ground relief (landforms and terrain), drainage (lakes and rivers),forest cover,administrative areas, populated areas, transportation routes and facilities (including roads and railways), and other man-made features.
Other authors define topographic maps by contrasting them with another type of map; they are distinguished from smaller-scale "chorographicmaps "that cover large regions,[3][4]"planimetricmaps "that do not show elevations,[5]and "thematic maps"that focus on specific topics.[6]
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".[4]
The study or discipline oftopographyis a much broader field of study, which takes into account allnaturaland human-made features of terrain. Maps were among the first artifacts to record observations about topography.[7]
History[edit]
Topographic maps are based on topographical surveys. Performed at large scales, these surveys are called topographical in the old sense oftopography,showing a variety of elevations and landforms.[8]This is in contrast to oldercadastral surveys,which primarily show property and governmental boundaries. The first multi-sheet topographic map series of an entire country, theCarte géométrique de la France,was completed in 1789.[9]TheGreat Trigonometric Surveyof India, started by theEast India Companyin 1802, then taken over by theBritish Rajafter 1857 was notable as a successful effort on a larger scale and for accurately determining heights of Himalayan peaks from viewpoints over one hundred miles distant.[10]
Topographic surveys were prepared by the military to assist in planning for battle and for defensive emplacements (thus the name and history of theUnited Kingdom'sOrdnance Survey). As such, elevation information was of vital importance.[11]
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 theArmy Corps of Engineersand theDepartment of the Interiormigrated to the newly createdUnited States Geological Surveyin 1879, where it has remained since.[12][13]
1913 saw the beginning of theInternational Map of the Worldinitiative, which set out to map all of Earth's significant land areas at a scale of 1:1 million, on about one thousand sheets, each covering four degrees latitude by six or more degrees longitude. Excluding borders, each sheet was 44 cm high and (depending on latitude) up to 66 cm wide. Although the project eventually foundered, it left anindexing systemthat remains in use.
By the 1980s, centralized printing of standardized topographic maps began to be superseded by databases of coordinates that could be used on computers by moderately skilled end users to view or print maps with arbitrary contents, coverage and scale. For example, thefederal government of the United States'TIGERinitiative compiled interlinked databases of federal, state and local politicalbordersandcensus enumeration areas,and of roadways, railroads, and water features with support for locating street addresses within street segments. TIGER was developed in the 1980s and used in the 1990 and subsequentdecennial censuses.Digital elevation models(DEM) were also compiled, initially from topographic maps and stereographic interpretation of aerial photographs and then fromsatellite photography and radar data.Since all these were government projects funded with taxes and not classified for national security reasons, the datasets were in thepublic domainand freely usable without fees or licensing.
TIGER and DEM datasets greatly facilitatedgeographic information systemsand made theGlobal Positioning Systemmuch more useful by providing context around locations given by the technology as coordinates. Initial applications were mostly professionalized forms such as innovativesurveying instrumentsand agency-level GIS systems tended by experts. By the mid-1990s, increasinglyuser-friendlyresources such asonline mappingin two and three dimensions, integration of GPS withmobile phonesandautomotive navigation systemsappeared. As of 2011, the future of standardized, centrally printed topographical maps is left somewhat in doubt.[14][15]
Uses[edit]
Topographic maps have many multiple uses in the present day: any type of geographicplanningor large-scalearchitecture;Earth sciencesand many othergeographicdisciplines;miningand other Earth-based endeavours;civil engineeringand recreational uses such ashikingandorienteering.
It takes practice and skill to read and interpret a topographic map. This includes not only how to identify map features, but also how to interpret contour lines to infer landforms like cliffs, ridges, draws, etc. Training in map reading is often given in orienteering, scouting, and the military.[16]
Conventions[edit]
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.[17]
Topographic maps are also commonly calledcontour mapsortopo maps.In the United States, where the primary national series is organized by a strict 7.5-minute grid, they are often called orquadsor quadrangles.
Topographic maps conventionally showtopography,or land contours, by means ofcontour lines.Contour lines arecurvesthat connect contiguous points of the samealtitude(isohypse). In other words, every point on the marked line of 100 melevationis 100 m above mean sea level.
These maps usually show not only the contours, but also any significantstreamsor other bodies ofwater,forestcover, built-up areas or individual buildings (depending on scale), and other features and points of interest such as what direction those streams are flowing.
Most topographic maps were prepared usingphotogrammetricinterpretation ofaerial photographyusing astereoplotter.Modern mapping also employslidarand otherRemote sensingtechniques. Older topographic maps were prepared using traditionalsurveyinginstruments.
The cartographic style (content and appearance) of topographic maps is highly variable between national mapping organizations. Aesthetic traditions and conventions persist in topographic map symbology, particularly amongst European countries at medium map scales.[18]
Publishers of national topographic map series[edit]
Although virtually the entire terrestrial surface of Earth has been mapped at scale 1:1,000,000, medium and large-scale mapping has been accomplished intensively in some countries and much less in others.[19]Several commercial vendors supply international topographic map series.
According to 2007/2/ECEuropean directive,national mapping agencies ofEuropean Unioncountries must have publicly available services for searching, viewing and downloading their official map series.[20]Topographic maps produced by some of them are available under afree licensethat allows re-use, such as aCreative Commonslicense.[21]
See also[edit]
References[edit]
- ^Kent, Alexander (1 July 2009)."Topographic Maps: Methodological Approaches for Analyzing Cartographic Style".Journal of Map & Geography Libraries.5(2): 131–156.doi:10.1080/15420350903001187.S2CID128466975.Retrieved13 June2020.
- ^Government of Canada (8 April 2016)."National Topographic System Maps".Earth Sciences – Geography.Natural Resources Canada. Archived fromthe originalon 15 May 2016.Retrieved16 May2016.
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- ^P. D. A. Harvey,The History of Topographical Maps: Symbols, Pictures and Surveys,Thames and Hudson, 1980,ISBN0-500-24105-8,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."
- ^abArt & Architecture Thesaurusentry fortopographic mapsArchived7 June 2011 at theWayback Machine.
- ^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.
- ^M.-J. Kraak and F. Ormeling,Cartography: Visualization of Spatial Data,Longman, 1996,ISBN0-582-25953-3,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."
- ^Kent, A.J.; Hopfstock, A. (November 2018)."Topographic Mapping: Past, Present and Future".The Cartographic Journal.55(4): 305–308.doi:10.1080/00087041.2018.1576973.
- ^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 usinghachures.
- ^Library of Congress,Geography and Maps: General CollectionsArchived16 September 2017 at theWayback Machine
- ^Dickey, Parke A (October 1985)."Who discovered Mount Everest?".Eos.66(41): 54–59.Bibcode:1985EOSTr..66..697D.doi:10.1029/EO066i041p00697.Retrieved26 June2011.
- ^Peter Barber,The Map Book,Weidenfeld & Nicolson, 2005,ISBN0-297-84372-9,pp. 232, 250.
- ^ "Organizing the U.S. Geological Survey".The United States Geological Survey: 1879–1989.U.S. Geological Survey, U.S. Department of the Interior. 10 April 2000.Archivedfrom the original on 2 July 2007.Retrieved19 June2007.
- ^ "The Four Great Surveys of the West".The United States Geological Survey: 1879–1989.U.S. Geological Survey, U.S. Department of the Interior. 10 April 2000.Archivedfrom the original on 10 June 2007.Retrieved19 June2007.
- ^ Ramirez, J. Raul."Maps for the Future: A Discussion"(PDF).Archived fromthe original(PDF)on 22 November 2011.Retrieved1 July2011.
- ^Hurst, Paul (2010),Will we be lost without paper maps in the digital age?(PDF)(M.S. thesis), U.K.: University of Sheffield, pp. 1–18, archived fromthe original(PDF)on 2 October 2011,retrieved1 July2011
- ^US Department of the Army (2015).Map Reading and Land Navigation(PDF).Field Manual No. 3-25.26. Washington, DC.
{{cite book}}:CS1 maint: location missing publisher (link) - ^Ordnance Survey,Explorer Map SymbolsArchived1 November 2012 at theWayback Machine;Swisstopo,Conventional SignsArchived26 July 2011 at theWayback Machine;United States Geological Survey,Topographic Map SymbolsArchived10 September 2008 at theWayback Machine.
- ^Kent, Alexander J.; Vujakovic, Peter (August 2009). "Stylistic Diversity in European State 1: 50 000 Topographic Maps".The Cartographic Journal.46(3): 179–213.doi:10.1179/000870409x12488753453453.ISSN0008-7041.S2CID129681695.
- ^Pickles, John.Cartography, Digital Transitions, and Questions of History(PDF).International Cartographic Association, 1999. Ottawa. p. 17. Archived fromthe original(PDF)on 23 November 2011.Retrieved29 June2011.
- ^"L_2007108EN.01000101.xml".19 January 2022. Archived fromthe originalon 19 January 2022.Retrieved3 August2022.
- ^"Spanish IGN products license (in Spanish)"(PDF).Archived fromthe original(PDF)on 6 May 2022.Retrieved3 August2022.
External links[edit]
- USGS Topographic maps are downloadable as pdf filesfrom a searchable maporby a search if the map name is known.
- How a Topographic Map is Manufactured, History, and Other Information
- The International Cartographic Association (ICA) Commission on Topographic Mapping
