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Terrain or relief (also topographical relief) involves the vertical and horizontal dimensions of land surface. The term bathymetry is used to describe underwater relief, while
hypsometry Hypsometry () is the measurement of the elevation and depth of features of the Earth's surface relative to mean sea level. On Earth, the elevations can take on either positive or negative (below sea level) values. The distribution is theorised ...
studies terrain relative to sea level. The Latin word (the root of ''terrain'') means "earth." In physical geography, terrain is the lay of the land. This is usually expressed in terms of the elevation, slope, and orientation of terrain features. Terrain affects surface water flow and distribution. Over a large area, it can affect weather and climate patterns.


Importance

The understanding of terrain is critical for many reasons: * The terrain of a region largely determines its suitability for human settlement: flatter
alluvial plain An alluvial plain is a largely flat landform created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions, from which alluvial soil forms. A floodplain is part of the process, being the sma ...
s tend to have better farming soils than steeper, rockier uplands. * In terms of environmental quality, agriculture, hydrology and other interdisciplinary sciences; understanding the terrain of an area assists the understanding of watershed boundaries, drainage characteristics, drainage systems, groundwater systems,
water movement Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a s ...
, and impacts on water quality. Complex arrays of relief data are used as input parameters for hydrology transport models (such as the SWMM or DSSAM Models) to allow prediction of river water quality. * Understanding terrain also supports soil conservation, especially in agriculture.
Contour ploughing Contour bunding or contour farming or Contour ploughing is the farming practice of plowing and/or planting across a slope following its elevation contour lines. These contour lines create a water break which reduces the formation of rills and gu ...
is an established practice enabling sustainable agriculture on sloping land; it is the practice of ploughing along lines of equal elevation instead of up and down a slope. * Terrain is
militarily A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distinct ...
critical because it determines the ability of
armed forces A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distinct ...
to take and hold areas, and move troops and material into and through areas. An understanding of terrain is basic to both defensive and offensive strategy. The military usage of "terrain" is very broad, encompassing not only landform but land use and land cover, surface transport infrastructure, built structures and human geography, and, by extension under the term human terrain, even psychological, cultural, or economic factors. * Terrain is important in determining weather patterns. Two areas geographically close to each other may differ radically in precipitation levels or timing because of elevation differences or a "
rain shadow A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side. Evaporated moisture from water bodies (such as oceans and large lakes) is carrie ...
" effect. * Precise knowledge of terrain is vital in aviation, especially for low-flying routes and maneuvers ( see terrain collision avoidance) and airport altitudes. Terrain will also affect range and performance of radars and terrestrial radio navigation systems. Furthermore, a hilly or mountainous terrain can strongly impact the implementation of a new aerodrome and the orientation of its runways.


Relief

Relief (or ''local relief'') refers specifically to the quantitative measurement of vertical elevation change in a
landscape A landscape is the visible features of an area of land, its landforms, and how they integrate with natural or man-made features, often considered in terms of their aesthetic appeal.''New Oxford American Dictionary''. A landscape includes the ...
. It is the difference between maximum and minimum elevations within a given area, usually of limited extent. A relief can be described qualitatively, such as a "" or "" plain or
upland Upland or Uplands may refer to: Geography *Hill, an area of higher land, generally *Highland, an area of higher land divided into low and high points *Upland and lowland, conditional descriptions of a plain based on elevation above sea level *I ...
. The relief of a landscape can change with the size of the area over which it is measured, making the definition of the scale over which it is measured very important. Because it is related to the slope of surfaces within the area of interest and to the gradient of any streams present, the relief of a landscape is a useful metric in the study of the Earth's surface. Relief energy, which may be defined ''inter alia'' as "the maximum height range in a regular grid", is essentially an indication of the ruggedness or relative height of the terrain.


Geomorphology

Geomorphology is in large part the study of the formation of terrain or topography. Terrain is formed by concurrent processes operating on the underlying geological structures over
geological time The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronol ...
: * Geological processes: Migration of tectonic plates, faulting and folding, mountain formation, volcanic eruptions, etc. * Erosional processes: glacial, water, wind, chemical and gravitational (
mass movement Mass movement may refer to: * Mass movement (geology), the movement of rock and soil down slopes due to gravity * Mass movement (politics) A mass movement denotes a political party or movement which is supported by large segments of a population. P ...
); such as
landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...
s, downhill creep, flows, slumps, and rock falls. *
Extraterrestrial Extraterrestrial refers to any object or being beyond ( extra-) the planet Earth ( terrestrial). It is derived from the Latin words ''extra'' ("outside", "outwards") and ''terrestris'' ("earthly", "of or relating to the Earth"). It may be abbrevia ...
:
meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...
impacts. Tectonic processes such as
orogenies Orogeny is a mountain building process. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. An ''orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is uplifted t ...
and uplifts cause land to be elevated, whereas erosional and weathering processes wear the land away by smoothing and reducing topographic features. The relationship of
erosion and tectonics The interaction between erosion and tectonics has been a topic of debate since the early 1990s. While the tectonic effects on surface processes such as erosion have long been recognized (for example, river formation as a result of tectonic uplift ...
rarely (if ever) reaches equilibrium. These processes are also codependent, however the full range of their interactions is still a topic of debate. Land surface parameters are quantitative measures of various
morphometric Morphometrics (from Greek μορϕή ''morphe'', "shape, form", and -μετρία ''metria'', "measurement") or morphometry refers to the quantitative analysis of ''form'', a concept that encompasses size and shape. Morphometric analyses are co ...
properties of a surface. The most common examples are used to derive slope or aspect of a terrain or curvatures at each location. These measures can also be used to derive hydrological parameters that reflect flow/erosion processes. Climatic parameters are based on the modelling of solar radiation or air flow. Land surface objects, or
landform A landform is a natural or anthropogenic land feature on the solid surface of the Earth or other planetary body. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography. Landforms include hills, ...
s, are definite physical objects (lines, points, areas) that differ from the surrounding objects. The most typical examples airlines of
watershed Watershed is a hydrological term, which has been adopted in other fields in a more or less figurative sense. It may refer to: Hydrology * Drainage divide, the line that separates neighbouring drainage basins * Drainage basin, called a "watershe ...
s,
stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...
patterns,
ridge A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The line ...
s, break-lines, pools or borders of specific landforms.


Digital terrain model


See also

* Applications of global navigation satellite systems (GNSS) * Cartographic relief depiction (2D relief map) *
Geographic information system A geographic information system (GIS) is a type of database containing Geographic data and information, geographic data (that is, descriptions of phenomena for which location is relevant), combined with Geographic information system software, sof ...
(GIS) * Geomorphometry *
Hypsometry Hypsometry () is the measurement of the elevation and depth of features of the Earth's surface relative to mean sea level. On Earth, the elevations can take on either positive or negative (below sea level) values. The distribution is theorised ...
* Isostasy *
Physical terrain model A raised-relief map, terrain model or embossed map is a three-dimensional representation, usually of terrain, materialized as a physical artifact. When representing terrain, the vertical dimension is usually exaggerated by a factor between fiv ...
*
Relief ratio The relief ratio is a number calculated to describe the grade of a river or stream. The calculation is the difference in elevation between the river's source and the river's confluence or mouth divided by the total length of the river or stream. ...
* Subterranea * Terrain awareness and warning system * Terrane * Topography


References


Bibliography

* * *


Further reading


Boots on the ground
On military terrain from the perspective of the combat soldier. By Professor Derek Gregory


External links


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{{Wiktionary-inline, terrain Physical geography Topography Vertical datums