HOME

TheInfoList




Topography is the study of the forms and features of
land surface Terrain or relief (also topographical Topography is the study of the forms and features of land surface Relief map of Sierra Nevada, Spain Terrain or relief (also topographical Topography is the study of the forms and fe ...
s. The topography of an area could refer to the surface forms and features themselves, or a description (especially their
depiction Depiction is reference conveyed through pictures. A picture refers to its object through a non-linguistic two-dimensional scheme, and is distinct from writing or notation. A depictive two-dimensional scheme is called a picture plane and may be cons ...
in maps). Topography is a field of
geoscience Earth science or geoscience includes all fields of natural science Natural science is a branch A branch ( or , ) or tree branch (sometimes referred to in botany Botany, also called , plant biology or phytology, is the science o ...
and
planetary science Planetary science (or more rarely, planetology) is the scientific study of planets (including Earth), Astronomical object, celestial bodies (such as Natural satellite, moons, Asteroid, asteroids, Comets on Fire, comets) and planetary systems (in p ...
and is concerned with local detail in general, including not only
relief Relief is a sculptural technique where the sculpted elements remain attached to a solid background of the same material. The term ''wikt:relief, relief'' is from the Latin verb ''relevo'', to raise. To create a sculpture in relief is to give the ...
, but also
natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and ...

natural
and
artificial Artificiality (the state of being artificial or man-made) is the state of being the product of intentional human manufacture, rather than occurring nature, naturally through processes not involving or requiring human activity. Connotations Artific ...
features, and even
local history Local history is the study of history History (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southea ...
and
culture Culture () is an umbrella term which encompasses the social behavior and Norm (social), norms found in human Society, societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, and habits of the individuals i ...

culture
. This meaning is less common in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

United States
, where topographic maps with
elevation The elevation of a geographic Geography (from Ancient Greek, Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth and Solar Sy ...

elevation
contours have made ''topography'' synonymous with ''relief''. Topography in a narrow sense involves the recording of relief or
terrain Terrain or relief (also topographical Topography is the study of the forms and features of land surface Relief map of Sierra Nevada, Spain Terrain or relief (also topographical Topography is the study of the forms and fe ...

terrain
, the three-dimensional quality of the surface, and the identification of specific
landform A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws ...

landform
s; this is also known as
geomorphometry Geomorphometry, or geomorphometrics ( grc, γῆ, gê, earth + grc, μορφή, morphḗ, form, shape + grc, μέτρον, métron, measure), is the science and practice of measuring the characteristics of terrain Terrain or relief (also ...
. In modern usage, this involves generation of elevation data in digital form (
DEM DEM was the ISO 4217 ISO 4217 is a standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requirement * Standard (metrology), an ob ...
). It is often considered to include the graphic representation of the landform on a
map A map is a symbol A symbol is a mark, sign, or that indicates, signifies, or is understood as representing an , , or . Symbols allow people to go beyond what is n or seen by creating linkages between otherwise very different s and s. A ...

map
by a variety of
cartographic relief depiction Terrain cartography or relief mapping is the depiction of the shape of the surface of the Earth on a map, using one or more of several techniques that have been developed. Terrain Terrain or relief (also topographical Topography i ...
techniques, including
contour line A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve In mathematics, a curve (also called a curved line in older texts) is an object similar to a line (geometry), line, but that does not have to b ...
s,
hypsometric tints Hypsometric tints (also called layer tinting, elevation tinting, elevation coloring, or hysometric coloring) are colors placed between contour lines A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a ...
, and relief shading.


Etymology

The term ''topography'' originated in
ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a civilization belonging to a period of History of Greece, Greek history from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, antiquity ( AD 600). This era wa ...
and continued in
ancient Rome In historiography Historiography is the study of the methods of historian ( 484– 425 BC) was a Greek historian who lived in the 5th century BC and one of the earliest historians whose work survives. A historian is a person who stud ...
, as the detailed description of a place. The word comes from the
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
(''topos'', "place") and (''-graphia'', "writing"). In classical literature this refers to writing about a place or places, what is now largely called '
local history Local history is the study of history History (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southea ...
'. In Britain and in Europe in general, the word topography is still sometimes used in its original sense. Detailed military surveys in
Britain Britain usually refers to: * United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a synonym for the United ...

Britain
(beginning in the late eighteenth century) were called
Ordnance Survey , nativename_a = , nativename_r = , logo = Ordnance Survey 2015 Logo.svg , logo_width = 240px , logo_caption = , seal = , seal_width = , seal_caption = , picture = , picture_width = , picture_caption = , formed = , preceding1 = , di ...
s, and this term was used into the 20th century as generic for topographic surveys and maps. The earliest scientific surveys in France were called the Cassini maps after the family who produced them over four generations. The term "topographic surveys" appears to be American in origin. The earliest detailed surveys in the United States were made by the "Topographical Bureau of the Army," formed during the
War of 1812 The War of 1812 (18 June 1812 – 17 February 1815) was a conflict fought by the United States of America The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country in . It ...
, which became the
Corps of Topographical Engineers The U.S. Army Corps of Topographical Engineers was a branch of the United States Army The United States Army (USA) is the land Land is the solid surface of Earth that is not permanently submerged in water. Most but not all land is sit ...
in 1838. After the work of national mapping was assumed by the
U.S. Geological Survey The United States Geological Survey (USGS, formerly simply Geological Survey) is a scientific agency Agency may refer to: * a governmental or other institution Institutions, according to Samuel P. Huntington, are "stable, valued, recurrin ...
in 1878, the term topographical remained as a general term for detailed surveys and mapping programs, and has been adopted by most other nations as standard. In the 20th century, the term topography started to be used to describe surface description in other fields where
map A map is a symbol A symbol is a mark, sign, or that indicates, signifies, or is understood as representing an , , or . Symbols allow people to go beyond what is n or seen by creating linkages between otherwise very different s and s. A ...

map
ping in a broader sense is used, particularly in medical fields such as
neurology Neurology (from el, , "string, nerve" and the suffix , "study of") is a branch of dealing with . Neurology deals with the diagnosis and treatment of all categories of conditions and disease involving the and s (and their subdivisions, the ...
.


Objectives

An objective of topography is to determine the position of any feature or more generally any point in terms of both a horizontal
coordinate system In geometry Geometry (from the grc, γεωμετρία; ' "earth", ' "measurement") is, with , one of the oldest branches of . It is concerned with properties of space that are related with distance, shape, size, and relative position o ...

coordinate system
such as latitude, longitude, and
altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum Data (; ) are individual facts A fact is something that is truth, true. The usual t ...

altitude
. Identifying (naming) features, and recognizing typical landform patterns are also part of the field. A
topographic study
topographic study
may be made for a variety of reasons: military planning and geological exploration have been primary motivators to start survey programs, but detailed information about
terrain Terrain or relief (also topographical Topography is the study of the forms and features of land surface Relief map of Sierra Nevada, Spain Terrain or relief (also topographical Topography is the study of the forms and fe ...

terrain
and surface features is essential for the
planning Planning is the process A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process A business p ...

planning
and
construction Construction is a general term meaning the and to form , , or ,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and comes from ''constructio'' (from ''com-' ...

construction
of any major
civil engineering Civil engineering is a professional engineering Regulation and licensure in engineering is established by various jurisdictions of the world to encourage public welfare, safety, well-being and other interests of the general public and to defin ...
,
public works Public works are a broad category of infrastructure Infrastructure is the set of fundamental facilities and systems that support the sustainable functionality of households and firms. Serving a country, city, or other area, including the serv ...

public works
, or reclamation projects.


Techniques

There are a variety of approaches to studying topography. Which method(s) to use depends on the scale and size of the area under study, its accessibility, and the quality of existing surveys.


Field survey

Surveying helps determine accurately the terrestrial or
three-dimensional space Three-dimensional space (also: 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called parameters) are required to determine the position of an element (i.e., point). This is the informal meaning of the ...
position of points and the distances and
angle In Euclidean geometry Euclidean geometry is a mathematical system attributed to Alexandrian Greek mathematics , Greek mathematician Euclid, which he described in his textbook on geometry: the ''Euclid's Elements, Elements''. Euclid's method ...

angle
s between them using
leveling instrument A level is an optical instrument used to establish or verify points in the same horizontal plane in a process known as levelling, and is used in conjunction with a levelling staff to establish the relative heights levels of objects or marks. It is ...
s such as
theodolite A theodolite is a precision optical instrument for measuring angle In Euclidean geometry Euclidean geometry is a mathematical system attributed to Alexandrian Greek mathematics , Greek mathematician Euclid, which he described in his text ...

theodolite
s,
dumpy level A level is an optical instrument used to establish or verify points in the same horizontal plane in a process known as levelling, and is used in conjunction with a levelling staff to establish the relative heights levels of objects or marks. It is ...
s and
clinometer An inclinometer or clinometer is an measuring instrument, instrument used for measuring angles of slope, elevation, or depression (geology), depression of an object with respect to gravity's direction. It is also known as a ''tilt indicator'', ' ...
s. Work on one of the first topographic maps was begun in France by
Giovanni Domenico Cassini Giovanni Domenico Cassini, also known as Jean-Dominique Cassini (8 June 1625 – 14 September 1712) was an Italian (naturalised French) mathematician, astronomer An astronomer is a scientist in the field of astronomy who focuses their stu ...

Giovanni Domenico Cassini
, the great Italian astronomer. Even though remote sensing has greatly sped up the process of gathering information, and has allowed greater accuracy control over long distances, the direct survey still provides the basic control points and framework for all topographic work, whether manual or
GIS A geographic information system (GIS) is a type of database In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processe ...

GIS
-based. In areas where there has been an extensive direct survey and mapping program (most of Europe and the Continental U.S., for example), the compiled data forms the basis of basic digital elevation datasets such as
USGS DEM The USGS DEM standard is a geospatial file format developed by the United States Geological Survey for storing a Raster graphics, raster-based digital elevation model. It is an open standard, and is used throughout the world. It has been superseded ...
data. This data must often be "cleaned" to eliminate discrepancies between surveys, but it still forms a valuable set of information for large-scale analysis. The original American topographic surveys (or the British "Ordnance" surveys) involved not only recording of relief, but identification of landmark features and vegetative land cover.


Remote sensing

Remote sensing Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object, in contrast to in situ ''In situ'' (; often not italicized in English) is a Latin Latin (, or , ) is a class ...

Remote sensing
is a general term for geodata collection at a distance from the subject area.


Passive sensor methodologies

Besides their role in photogrammetry, aerial and satellite imagery can be used to identify and delineate terrain features and more general land-cover features. Certainly they have become more and more a part of
geovisualization Geovisualization or geovisualisation (short for geographic visualization), also known as cartographic visualization, refers to a set of tools and techniques supporting the analysis of geospatial data Geographic data and information is defined in t ...
, whether
map A map is a symbol A symbol is a mark, sign, or that indicates, signifies, or is understood as representing an , , or . Symbols allow people to go beyond what is n or seen by creating linkages between otherwise very different s and s. A ...

map
s or
GIS A geographic information system (GIS) is a type of database In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processe ...

GIS
systems. False-color and non-visible
spectra
spectra
imaging can also help determine the lie of the land by delineating vegetation and other land-use information more clearly. Images can be in visible colours and in other spectrum.


Photogrammetry

Photogrammetry is a measurement technique for which the co-ordinates of the points in 3D of an object are determined by the measurements made in two
photographic Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is employed i ...
image An image (from la, imago) is an artifact that depicts visual perception Visual perception is the ability to interpret the surrounding environment (biophysical), environment through photopic vision (daytime vision), color vision, sco ...

image
s (or more) taken starting from different positions, usually from different passes of an aerial photography flight. In this technique, the common points are identified on each image. A line of sight (or
ray Ray may refer to: Science and mathematics * Ray (geometry) In geometry, the notion of line or straight line was introduced by ancient mathematicians to represent straight objects (i.e., having no curvature) with negligible width and depth. ...
) can be built from the camera location to the point on the object. It is the intersection of its rays (
triangulation In trigonometry Trigonometry (from Greek '' trigōnon'', "triangle" and '' metron'', "measure") is a branch of mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathe ...

triangulation
) which determines the relative three-dimensional position of the point. Known control points can be used to give these relative positions absolute values. More sophisticated
algorithm In and , an algorithm () is a finite sequence of , computer-implementable instructions, typically to solve a class of problems or to perform a computation. Algorithms are always and are used as specifications for performing s, , , and other ...

algorithm
s can exploit other information on the scene known a priori (for example, symmetries in certain cases allowing the rebuilding of three-dimensional co-ordinates starting from one only position of the camera).


Active sensor methodologies

Satellite
RADAR Radar (radio detection and ranging) is a detection system that uses radio waves to determine the distance (''ranging''), angle, or velocity of objects. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor ...

RADAR
mapping is one of the major techniques of generating Digital Elevation Models (see below). Similar techniques are applied in
bathymetric Bathymetry (pronounced ) is the study of underwater depth of ocean floor The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface of the Earth.
bathymetric
surveys using
sonar Sonar (sound navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect objects on or under the surface o ...

sonar
to determine the terrain of the ocean floor. In recent years,
LIDAR Lidar (, also LIDAR, or LiDAR; sometimes LADAR) is a method for determining ranges (variable distance) by targeting an object with a laser A laser is a device that emits light Light or visible light is electromagnetic radiati ...
(LIght Detection And Ranging), a remote sensing technique that uses a laser instead of radio waves, has increasingly been employed for complex mapping needs such as charting canopies and monitoring glaciers.


Forms of topographic data

Terrain is commonly modelled either using vector (
triangulated irregular network A triangulated irregular network (TIN) is a representation of a continuous surface consisting entirely of triangular facets (a triangle mesh), used mainly as Discrete Global Grid A Discrete Global Grid (DGG) is a tessellation, mosaic which cove ...
or TIN) or gridded (
Raster image file:Rgb-raster-image.svg, upright=1, The Smiley, smiley face in the top left corner is a raster image. When enlarged, individual pixels appear as squares. Enlarging further, each pixel can be analyzed, with their colors constructed through comb ...

Raster image
) mathematical models. In the most applications in
environmental science Environmental science is an interdisciplinary Interdisciplinarity or interdisciplinary studies involves the combination of two or more academic disciplines into one activity (e.g., a research project). It draws knowledge from several oth ...
s, land surface is represented and modelled using gridded models. In civil engineering and entertainment businesses, the most representations of land surface employ some variant of TIN models. In
geostatistics Geostatistics is a branch of statistics Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data Data (; ) are individual facts, statistics, or items of informati ...
, land surface is commonly modelled as a combination of the two signals – the smooth (spatially correlated) and the rough (noise) signal. In practice, surveyors first sample heights in an area, then use these to produce a Digital Land Surface Model in the form of a
TIN Tin is a with the Sn (from la, ) and  50. Tin is a silvery-colored metal that characteristically has a faint yellow hue. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent ...
. The DLSM can then be used to visualize terrain, drape remote sensing images, quantify ecological properties of a surface or extract land surface objects. Note that the contour data or any other sampled elevation datasets are not a DLSM. A DLSM implies that elevation is available continuously at each location in the study area, i.e. that the map represents a complete surface. Digital Land Surface Models should not be confused with Digital Surface Models, which can be surfaces of the canopy, buildings and similar objects. For example, in the case of surface models produces using the lidar technology, one can have several surfaces – starting from the top of the canopy to the actual solid earth. The difference between the two surface models can then be used to derive volumetric measures (height of trees etc.).


Raw survey data

Topographic survey information is historically based upon the notes of surveyors. They may derive naming and cultural information from other local sources (for example,
boundary Boundary or Boundaries may refer to: * Border, in political geography Entertainment *Boundaries (2016 film), ''Boundaries'' (2016 film), a 2016 Canadian film *Boundaries (2018 film), ''Boundaries'' (2018 film), a 2018 American-Canadian road trip ...
delineation may be derived from local
cadastral A cadastral map (shortened to cadastre or cadaster) is a comprehensive land recording of the real estate Real estate is property consisting of land and the buildings on it, along with its natural resources such as crops, minerals or water; i ...
mapping). While of historical interest, these field notes inherently include errors and contradictions that later stages in map production resolve.


Remote sensing data

As with field notes, remote sensing data (aerial and satellite photography, for example), is raw and uninterpreted. It may contain holes (due to cloud cover for example) or inconsistencies (due to the timing of specific image captures). Most modern topographic mapping includes a large component of remotely sensed data in its compilation process.


Topographic mapping

In its contemporary definition, topographic mapping shows relief. In the United States,
USGS The United States Geological Survey, abbreviated USGS and formerly simply known as the Geological Survey, is a scientific agency Agency may refer to: * a governmental or other institution Institutions, according to Samuel P. Huntington, ...
topographic maps show relief using contour lines. The USGS calls maps based on topographic surveys, but without contours, "planimetric maps." These maps 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. While not officially "topographic" maps, the national surveys of other nations share many of the same features, and so they are often called "topographic maps." Existing topographic survey maps, because of their comprehensive and encyclopedic coverage, form the basis for much derived topographic work. Digital Elevation Models, for example, have often been created not from new remote sensing data but from existing paper topographic maps. Many government and private publishers use the artwork (especially the contour lines) from existing topographic map sheets as the basis for their own specialized or updated topographic maps.See for example the publications o
National Geographic Trails Illustrated Maps
and DeLorme products.
Topographic mapping should not be confused with geologic mapping. The latter is concerned with underlying structures and processes to the surface, rather than with identifiable surface features.


Digital elevation modeling

The digital elevation model (DEM) is a raster graphics, raster-based Digital data, digital dataset of the topography (hypsometry and/or bathymetry) of all or part of the Earth (or a telluric planet). The pixels of the dataset are each assigned an elevation value, and a header portion of the dataset defines the area of coverage, the units each pixel covers, and the units of elevation (and the zero-point). DEMs may be derived from existing paper maps and survey data, or they may be generated from new satellite or other remotely sensed radar or
sonar Sonar (sound navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect objects on or under the surface o ...

sonar
data.


Topological modeling

A geographic information system (GIS) can recognize and analyze the spatial relationships that exist within digitally stored spatial data. These topological relationships allow complex spatial Model (abstract), modelling and analysis to be performed. Topological relationships between geometric entities traditionally include adjacency (what adjoins what), containment (what encloses what), and proximity (how close something is to something else). * reconstitute a sight in synthesized images of the ground, * determine a trajectory of overflight of the ground, * calculate surfaces or volumes, * trace topographic profiles,


Topography in other fields

Topography has been applied to different science fields. In neuroscience, the neuroimaging discipline uses techniques such as EEG topography for brain mapping. In ophthalmology, corneal topography is used as a technique for mapping the surface curvature of the cornea. In tissue engineering, atomic force microscopy is used to map nanotopography. In human anatomy, topography is superficial human anatomy. In mathematics the concept of topography is used to indicate the patterns or general organization of features on a map or as a term referring to the pattern in which variables (or their values) are distributed in a space.


Topographers

Topographers are experts in topography.


See also

* Cartography * Digital elevation model * Fall line (topography) * Geomorphology * Global Relief Model * Hypsography * Marine topography * Topographic map


References

{{Authority control Topography, Cartography