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46-591: Topography is a field of geoscience and planetary science and is concerned with local detail in general, including not only relief , but also natural , artificial, and cultural features such as roads, land boundaries, and buildings. In the United States, topography often means specifically relief , even though the USGS topographic maps record not just elevation contours, but also roads, populated places, structures, land boundaries, and so on. Topography in

92-413: A broader sense is used, particularly in medical fields such as neurology . 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 such as latitude, longitude, and altitude . Identifying (naming) features, and recognizing typical landform patterns are also part of the field. A topographic study may be made for

138-589: A narrow sense involves the recording of relief or terrain , the three-dimensional quality of the surface, and the identification of specific landforms ; this is also known as geomorphometry . In modern usage, this involves generation of elevation data in digital form ( DEM ). It is often considered to include the graphic representation of the landform on a map by a variety of cartographic relief depiction techniques, including contour lines , hypsometric tints , and relief shading . The term topography originated in ancient Greece and continued in ancient Rome , as

184-486: 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. Terrain is commonly modelled either using vector ( triangulated irregular network or TIN) or gridded ( raster image ) mathematical models. In the most applications in environmental sciences , land surface is represented and modelled using gridded models. In civil engineering and entertainment businesses,

230-420: A surface or extract land surface objects. 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

276-405: A variety of reasons: military planning and geological exploration have been primary motivators to start survey programs, but detailed information about terrain and surface features is essential for the planning and construction of any major civil engineering , public works , or reclamation projects. There are a variety of approaches to studying topography. Which method(s) to use depends on

322-473: 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 are experts in topography. They study and describe the surface features of a place or region. Geoscience Earth science or geoscience includes all fields of natural science related to

368-413: Is a general term for geodata collection at a distance from the subject area. 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 , whether maps or GIS systems. False-color and non-visible spectra imaging can also help determine

414-460: Is concerned with underlying structures and processes to the surface, rather than with identifiable surface features. The digital elevation model (DEM) is a raster -based 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

460-417: Is created are called divergent boundaries , those where it is brought back into the Earth are convergent boundaries and those where plates slide past each other, but no new lithospheric material is created or destroyed, are referred to as transform (or conservative) boundaries. Earthquakes result from the movement of the lithospheric plates, and they often occur near convergent boundaries where parts of

506-522: Is distinct from human geography , which studies the human populations on Earth, though it does include human effects on the environment. Methodologies vary depending on the nature of the subjects being studied. Studies typically fall into one of three categories: observational, experimental, or theoretical. Earth scientists often conduct sophisticated computer analysis or visit an interesting location to study earth phenomena (e.g. Antarctica or hot spot island chains). A foundational idea in Earth science

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552-470: Is largely the study of the lithosphere , or Earth's surface, including the crust and rocks . It includes the physical characteristics and processes that occur in the lithosphere as well as how they are affected by geothermal energy . It incorporates aspects of chemistry, physics, and biology as elements of geology interact. Historical geology is the application of geology to interpret Earth history and how it has changed over time. Geochemistry studies

598-525: 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. In its contemporary definition, topographic mapping shows relief. In the United States, USGS 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

644-518: Is represented by a field of a magnetic dipole currently tilted at an angle of about 11° with respect to Earth's rotational axis, as if there were an enormous bar magnet placed at that angle through the center of Earth. The North geomagnetic pole ( Ellesmere Island , Nunavut , Canada) actually represents the South pole of Earth's magnetic field, and conversely the South geomagnetic pole corresponds to

690-420: Is the notion of uniformitarianism , which states that "ancient geologic features are interpreted by understanding active processes that are readily observed." In other words, any geologic processes at work in the present have operated in the same ways throughout geologic time. This enables those who study Earth history to apply knowledge of how the Earth's processes operate in the present to gain insight into how

736-526: Is the study of minerals and includes the study of mineral formation, crystal structure , hazards associated with minerals, and the physical and chemical properties of minerals. Petrology is the study of rocks, including the formation and composition of rocks. Petrography is a branch of petrology that studies the typology and classification of rocks. Plate tectonics , mountain ranges , volcanoes , and earthquakes are geological phenomena that can be explained in terms of physical and chemical processes in

782-441: Is the study of oceans. Hydrogeology is the study of groundwater . It includes the mapping of groundwater supplies and the analysis of groundwater contaminants. Applied hydrogeology seeks to prevent contamination of groundwater and mineral springs and make it available as drinking water . The earliest exploitation of groundwater resources dates back to 3000 BC, and hydrogeology as a science was developed by hydrologists beginning in

828-422: Is to something else). 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

874-590: The solar wind , a stream of charged particles emanating from the Sun . The magnetic field is generated by electric currents due to the motion of convection currents of a mixture of molten iron and nickel in Earth's outer core : these convection currents are caused by heat escaping from the core, a natural process called a geodynamo . The magnitude of Earth's magnetic field at its surface ranges from 25 to 65 μT (0.25 to 0.65 G). As an approximation, it

920-649: The "Topographical Bureau of the Army", formed during the War of 1812 , which became the Corps of Topographical Engineers in 1838. After the work of national mapping was assumed by the U.S. Geological Survey 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 mapping in

966-427: The 17th century. Ecohydrology is the study of ecological systems in the hydrosphere . It can be divided into the physical study of aquatic ecosystems and the biological study of aquatic organisms. Ecohydrology includes the effects that organisms and aquatic ecosystems have on one another as well as how these ecoystems are affected by humans. Glaciology is the study of the cryosphere, including glaciers and coverage of

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1012-604: The Continental U.S., for example), the compiled data forms the basis of basic digital elevation datasets such as USGS DEM 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

1058-500: The Earth by ice and snow. Concerns of glaciology include access to glacial freshwater, mitigation of glacial hazards, obtaining resources that exist beneath frozen land, and addressing the effects of climate change on the cryosphere. Ecology is the study of the biosphere . This includes the study of nature and of how living things interact with the Earth and one another and the consequences of that. It considers how living things use resources such as oxygen , water , and nutrients from

1104-425: The Earth to sustain themselves. It also considers how humans and other living creatures cause changes to nature. Physical geography is the study of Earth's systems and how they interact with one another as part of a single self-contained system. It incorporates astronomy, mathematical geography, meteorology, climatology, geology, geomorphology, biology, biogeography, pedology, and soils geography. Physical geography

1150-402: The Earth's crust. Beneath the Earth's crust lies the mantle which is heated by the radioactive decay of heavy elements . The mantle is not quite solid and consists of magma which is in a state of semi-perpetual convection . This convection process causes the lithospheric plates to move, albeit slowly. The resulting process is known as plate tectonics. Areas of the crust where new crust

1196-485: The Earth's surface from cosmic rays . The magnetic field —created by the internal motions of the core—produces the magnetosphere which protects Earth's atmosphere from the solar wind . As the Earth is 4.5 billion years old, it would have lost its atmosphere by now if there were no protective magnetosphere. Earth's magnetic field , also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with

1242-669: 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 data. 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 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

1288-482: The atmosphere is made up of about 78.0% nitrogen , 20.9% oxygen , and 0.92% argon , and small amounts of other gases including CO 2 and water vapor. Water vapor and CO 2 cause the Earth's atmosphere to catch and hold the Sun's energy through the greenhouse effect . This makes Earth's surface warm enough for liquid water and life. In addition to trapping heat, the atmosphere also protects living organisms by shielding

1334-454: 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. Topographic mapping should not be confused with geologic mapping . The latter

1380-747: 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.). 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 delineation may be derived from local cadastral mapping). While of historical interest, these field notes inherently include errors and contradictions that later stages in map production resolve. As with field notes, remote sensing data (aerial and satellite photography, for example),

1426-580: The chemical components and processes of the Earth. Geophysics studies the physical properties of the Earth. Paleontology studies fossilized biological material in the lithosphere. Planetary geology studies geoscience as it pertains to extraterrestrial bodies. Geomorphology studies the origin of landscapes. Structural geology studies the deformation of rocks to produce mountains and lowlands. Resource geology studies how energy resources can be obtained from minerals. Environmental geology studies how pollution and contaminants affect soil and rock. Mineralogy

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1472-414: The common points are identified on each image . A line of sight (or ray ) can be built from the camera location to the point on the object. It is the intersection of its rays ( 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 algorithms can exploit other information on

1518-454: 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

1564-443: The convecting mantle. Volcanoes result primarily from the melting of subducted crust material. Crust material that is forced into the asthenosphere melts, and some portion of the melted material becomes light enough to rise to the surface—giving birth to volcanoes. Atmospheric science initially developed in the late-19th century as a means to forecast the weather through meteorology , the study of weather. Atmospheric chemistry

1610-405: The crust are forced into the earth as part of subduction. Plate tectonics might be thought of as the process by which the Earth is resurfaced. As the result of seafloor spreading , new crust and lithosphere is created by the flow of magma from the mantle to the near surface, through fissures, where it cools and solidifies. Through subduction , oceanic crust and lithosphere vehemently returns to

1656-571: The detailed description of a place. The word comes from the Greek τόπος ( topos , "place") and -γραφία ( -graphia , "writing"). In classical literature this refers to writing about a place or places, what is now largely called ' local history '. In Britain and in Europe in general, the word topography is still sometimes used in its original sense. Detailed military surveys in Britain (beginning in

1702-538: The first topographic maps was begun in France by 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 -based. In areas where there has been an extensive direct survey and mapping program (most of Europe and

1748-457: The late eighteenth century) were called Ordnance Surveys , and this term was used into the 20th century as generic for topographic surveys and maps. The earliest scientific surveys in France were 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

1794-456: 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 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 images (or more) taken starting from different positions, usually from different passes of an aerial photography flight. In this technique,

1840-479: The most representations of land surface employ some variant of TIN models. In geostatistics , 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 . The DLSM can then be used to visualize terrain, drape remote sensing images, quantify ecological properties of

1886-661: The north pole of Earth's magnetic field (because opposite magnetic poles attract and the north end of a magnet, like a compass needle, points toward Earth's South magnetic field. Hydrology is the study of the hydrosphere and the movement of water on Earth . It emphasizes the study of how humans use and interact with freshwater supplies. Study of water's movement is closely related to geomorphology and other branches of Earth science. Applied hydrology involves engineering to maintain aquatic environments and distribute water supplies. Subdisciplines of hydrology include oceanography , hydrogeology , ecohydrology , and glaciology . Oceanography

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1932-457: The planet Earth . This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spheres: the biosphere , hydrosphere / cryosphere , atmosphere , and geosphere (or lithosphere ). Earth science can be considered to be a branch of planetary science but with a much older history. Geology is broadly the study of Earth's structure, substance, and processes. Geology

1978-466: The planet has evolved and changed throughout long history. In Earth science, it is common to conceptualize the Earth's surface as consisting of several distinct layers, often referred to as spheres: the lithosphere , the hydrosphere , the atmosphere , and the biosphere , this concept of spheres is a useful tool for understanding the Earth's surface and its various processes these correspond to rocks , water , air and life . Also included by some are

2024-425: The scale and size of the area under study, its accessibility, and the quality of existing surveys. Surveying helps determine accurately the terrestrial or three-dimensional space position of points and the distances and angles between them using leveling instruments such as theodolites , dumpy levels and clinometers . GPS and other global navigation satellite systems (GNSS) are also used. Work on one of

2070-462: 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). Satellite RADAR mapping is one of the major techniques of generating Digital Elevation Models (see below). Similar techniques are applied in bathymetric surveys using sonar to determine the terrain of the ocean floor. In recent years, LIDAR ( LI ght D etection A nd R anging),

2116-405: Was developed in the 20th century to measure air pollution and expanded in the 1970s in response to acid rain . Climatology studies the climate and climate change . The troposphere , stratosphere , mesosphere , thermosphere , and exosphere are the five layers which make up Earth's atmosphere. 75% of the mass in the atmosphere is located within the troposphere, the lowest layer. In all,

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