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 studies terrain relative to sea level. The Latin word terra (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.
The understanding of terrain is critical for many reasons:
Relief (or local relief) refers specifically to the quantitative measurement of vertical elevation change in a landscape. It is the difference between maximum and minimum elevations within a given area, usually of limited extent. 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 is in large part the study of the formation of terrain or topography. Terrain is formed by concurrent processes:
Tectonic processes such as orogenies 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 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 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 landforms, are definite physical objects (lines, points, areas) that differ from the surrounding objects. The most typical examples airlines of watersheds, stream patterns, ridges, break-lines, pools or borders of specific landforms.
The dictionary definition of terrain at WiktionaryAll-terrain vehicle
An all-terrain vehicle (ATV), also known as a quad, three-wheeler, four-track, four-wheeler, or quadricycle, as defined by the American National Standards Institute (ANSI) is a vehicle that travels on low-pressure tires, with a seat that is straddled by the operator, along with handlebars for steering control. As the name implies, it is designed to handle a wider variety of terrain than most other vehicles. Although it is a street-legal vehicle in some countries, it is not street-legal within most states and provinces of Australia, the United States, or Canada.
By the current ANSI definition, ATVs are intended for use by a single operator, although some companies have developed ATVs intended for use by the operator and one passenger. In some countries, the passenger is not required to wear a helmet. These ATVs are referred to as tandem ATVs.The rider sits on and operates these vehicles like a motorcycle, but the extra wheels give more stability at slower speeds. Also dirt bikes are considered to be ATVs as that they were designed for off-road use only. Although most are equipped with three or four wheels, six-wheel models exist for specialized applications. Engine sizes of ATVs currently for sale in the United States, (as of 2008 products), range from 49 to 1,000 cc (0.049 to 1.0 L; 3.0 to 61 cu in).Brain terrain
Brain terrain, also called knobs-brain coral and brain coral terrain, is a feature of the Martian surface, consisting of complex ridges found on lobate debris aprons, lineated valley fill and concentric crater fill. It is so named because it suggests the ridges on the surface of the human brain. Wide ridges are called closed-cell brain terrain, and the less common narrow ridges are called open-cell brain terrain. It is thought that the wide closed-cell terrain contains a core of ice, and when the ice disappears the center of the wide ridge collapses to produce the narrow ridges of the open-cell brain terrain. Shadow measurements from HiRISE indicate the ridges are 4-5 meters high. Brain terrain has been observed to form from what has been called an "Upper Plains Unit." The process begins with the formation of stress cracks. The upper plains unit fell from the sky as snow and as ice coated dust.Today it is widely accepted that glacier-like forms, lobate debris aprons, lineated valley fill, and concentric fill are all related in that they have the same surface texture. Glacier-like forms in valleys and cirque-like alcoves may coalesce with others to produce lobate debris aprons. When opposing lobate debris aprons converge, linear valley fill results. They probably all contain ice-rich material.
Many of these features are found in the Northern hemisphere in parts of a boundary called the Martian dichotomy, mostly between 0 and 70 E longitudes. Near this area are regions that are named from ancient places: Deuteronilus Mensae, Protonilus Mensae, and Nilosyrtis Mensae.
Lobate debris aprons, lineated valley fill, and concentric fill probably have dirt and rock debris covering huge deposits of ice.Controlled flight into terrain
A controlled flight into terrain (CFIT, usually pronounced cee-fit) is an accident in which an airworthy aircraft, under pilot control, is unintentionally flown into the ground, a mountain, a body of water or an obstacle. In a typical CFIT scenario, the crew is unaware of the impending disaster until it is too late. The term was coined by engineers at Boeing in the late 1970s.Accidents where the aircraft is out of control at the time of impact, because of mechanical failure or pilot error, are not considered CFIT (they are known as uncontrolled flight into terrain), nor are incidents resulting from the deliberate action of the person at the controls, such as acts of terrorism or suicide by pilot.
According to Boeing, CFIT is a leading cause of airplane accidents involving the loss of life, causing over 9,000 deaths since the beginning of the commercial jet age. CFIT was identified as a cause of 25% of USAF Class A mishaps between 1993 and 2002.Digital elevation model
A digital elevation model (DEM) is a 3D CG representation of a terrain's surface – commonly of a planet (e.g. Earth), moon, or asteroid – created from a terrain's elevation data. A "global DEM" refers to a discrete global grid.
DEMs are used often in geographic information systems, and are the most common basis for digitally produced relief maps. While a digital surface model (DSM) may be useful for landscape modeling, city modeling and visualization applications, a digital terrain model (DTM) is often required for flood or drainage modeling, land-use studies, geological applications, and other applications, and in planetary science.Fretted terrain
Fretted terrain is a type of surface feature common to certain areas of Mars and was discovered in Mariner 9 images. It lies between two different types of terrain. The surface of Mars can be divided into two parts: low, young, uncratered plains that cover most of the northern hemisphere, and high-standing, old, heavily cratered areas that cover the southern and a small part of the northern hemisphere. Between these two zones is a region called the Martian dichotomy and parts of it contain fretted terrain. This terrain contains a complicated mix of cliffs, mesas, buttes, and straight-walled and sinuous canyons. It contains smooth, flat lowlands along with steep cliffs. The scarps or cliffs are usually 1 to 2 km high. Channels in the area have wide, flat floors and steep walls. Fretted terrain shows up in northern Arabia, between latitudes 30°N and 50°N and longitudes 270°W and 360°W, and in Aeolis Mensae, between 10 N and 10 S latitude and 240 W and 210 W longitude. Two good examples of fretted terrain are Deuteronilus Mensae and Protonilus Mensae.
Fretted terrain in Arabia Terra (Ismenius Lacus quadrangle), seems to transition from narrow straight valleys to isolated mesas. Most of the mesas are surrounded by forms that have been given a variety of names: circum-mesa aprons, debris aprons, rock glaciers, and lobate debris aprons. At first, they appeared to resemble rock glaciers on Earth. But scientists could not be sure. Even after the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) took a variety of pictures of fretted terrain, experts could not tell for sure if material was moving or flowing as it would in an ice-rich deposit (glacier). Eventually, proof of their true nature was discovered when radar studies with the Mars Reconnaissance Orbiter showed that they contained pure water ice covered with a thin layer of rocks that insulated the ice.Besides rock-covered glaciers around mesas, the region had many steep-walled valleys with lineations—ridges and grooves—on their floors. The material comprising these valley floors is called lineated valley fill. In some of the best images taken by the Viking Orbiters, some of the valley fill appeared to resemble alpine glaciers on Earth. Given this similarity, some scientists assumed that the lineations on these valley floors might have formed by flow of ice in (and perhaps through) these canyons and valleys. Today it is generally agreed that glacial flow caused the lineations.Fretted terrain in Aeolis Mensae is similar to that of Arabia Terra, but it lacks debris aprons and lineated valley fill. The Medusae Fossae Formation, a friable, layered material that is covered with yardangs surrounds parts of the fretted terrain in Aeolis Mensae.The origin of fretted plateau material is not completely understood. It does seem to contain fine-grained material, and it has an almost total lack of boulders. This material contrasts with most of the Martian surface which is covered with the igneous rock basalt. Basalt breaks into boulders and eventually into sand. It is thought that when plateau material breaks down, the small-sized particles can be easily carried away by the wind. Erosion of plateau material seems to be much faster than other materials on Mars. Research presented in 2018 at a Lunar and Planetary Science Conference in Texas suggested that the erosion that formed fretted terrain was aided by water moving under the surface.Geographical feature
Geographical features are naturally-created features of the Earth. Natural geographical features consist of landforms and ecosystems. For example, terrain types, (physical factors of the environment) are natural geographical features. Conversely, human settlements or other engineered forms are considered types of artificial geographical features.Glaciology
Glaciology (from Latin: glacies, "frost, ice", and Ancient Greek: λόγος, logos, "subject matter"; literally "study of ice") is the scientific study of glaciers, or more generally ice and natural phenomena that involve ice.
Glaciology is an interdisciplinary Earth science that integrates geophysics, geology, physical geography, geomorphology, climatology, meteorology, hydrology, biology, and ecology. The impact of glaciers on people includes the fields of human geography and anthropology. The discoveries of water ice on the Moon, Mars, Europa and Pluto add an extraterrestrial component to the field, which is referred to as "astroglaciology".Grade (slope)
The grade (also called slope, incline, gradient, mainfall, pitch or rise) of a physical feature, landform or constructed line refers to the tangent of the angle of that surface to the horizontal. It is a special case of the slope, where zero indicates horizontality. A larger number indicates higher or steeper degree of "tilt". Often slope is calculated as a ratio of "rise" to "run", or as a fraction ("rise over run") in which run is the horizontal distance (not the distance along the slope) and rise is the vertical distance.
The grades or slopes of existing physical features such as canyons and hillsides, stream and river banks and beds are often described. Grades are typically specified for new linear constructions (such as roads, landscape grading, roof pitches, railroads, aqueducts, and pedestrian or bicycle circulation routes). The grade may refer to the longitudinal slope or the perpendicular cross slope.Height above average terrain
Height above average terrain (HAAT), or (less popularly) effective height above average terrain (EHAAT), is a measure of how high an antenna site is above the surrounding landscape. HAAT is used extensively in FM radio and television, as it is more important than effective radiated power (ERP) in determining the range of broadcasts (VHF and UHF in particular, as they are line of sight transmissions). For international coordination, it is officially measured in meters, even by the Federal Communications Commission in the United States, as Canada and Mexico have extensive border zones where stations can be received on either side of the international boundaries. Stations that want to increase above a certain HAAT must reduce their power accordingly, based on the maximum distance their station class is allowed to cover (see List of North American broadcast station classes for more information on this).
The FCC procedure to calculate HAAT is: from the proposed or actual antenna site, either 12 or 16 radials were drawn, and points at 2, 4, 6, 8, and 10 miles (16 km) radius along each radial were used. The entire radial graph could be rotated to achieve the best effect for the station. The altitude of the antenna site, minus the average altitude of all the specified points, is the HAAT. This can create some unusual cases, particularly in mountainous regions—it is possible to have a negative number for HAAT (the transmitter would not be located underground, but rather in a valley, with hills on both sides taller than the transmitter itself, for example).
The FCC has divided the Contiguous United States into three zones for the determination of spacing between FM and TV stations using the same frequencies. FM and TV stations are assigned maximum ERP and HAAT values, depending on their assigned zones, to prevent co-channel interference.
The FCC regulations for ERP and HAAT are listed under Title 47, Part 73 of the Code of Federal Regulations (CFR).Iani Chaos
Iani Chaos is a region of chaos terrain at the south end of the outflow channel Ares Vallis, of the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars, centered at approximately ~342°E, 2°S. This is the source region of Ares Vallis. The chaotic terrain is widely believed to have formed via the removal of subsurface water or ice, resulting in flooding at the surface, and the formation of Ares Vallis. Within Iani Chaos, deposited stratigraphically above the chaotic terrain, are smooth, low-slope, intermediate-to-light-toned deposits that are rich in a hydrated mineral that is most likely gypsum as well as hematite.Jungle
A jungle is land covered with dense vegetation dominated by trees. Application of the term has varied greatly during the past recent centuries. Before the 1970s, tropical rainforests were generally referred to as jungles but this terminology has fallen out of usage. Jungles in Western literature can represent a less civilised or unruly space outside the control of civilisation, attributed to the jungle's association in colonial discourse with places colonised by Europeans.Landform
A landform is a natural or artificial feature of 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. Typical landforms include hills, mountains, plateaus, canyons, and valleys, as well as shoreline features such as bays, peninsulas, and seas, including submerged features such as mid-ocean ridges, volcanoes, and the great ocean basins.Mountain bike
A mountain bike or mountain bicycle (abbreviated MTB) is a bicycle designed for off-road cycling. Mountain bikes share similarities with other bicycles, but incorporate features designed to enhance durability and performance in rough terrain. These typically include a front or full suspension, large knobby tires, more durable wheels, more powerful brakes, straight handlebars, and lower gear ratios for climbing steep grades.Mountain bikes are generally specialized for use on mountain trails, single track, fire roads, and other unpaved surfaces, although perhaps the majority of them are never used off pavement, and it is common to find hybrid road bikes based on "mountain bike" frames for sale. This type of terrain commonly has rocks, roots, loose dirt, and steep grades. Many trails have additional TTFs (Technical Trail Features) such as log piles, log rides, rock gardens, skinnies, gap jumps, and wall-rides. Mountain bikes are built to handle these types of terrain and features. The heavy-duty construction combined with stronger rims and wider tires has also made this style of bicycle popular with urban riders and couriers who must navigate through potholes and over curbs.Since the development of the sport in the 1970s, many new subtypes of mountain biking have developed, such as cross-country (XC), all-day endurance, freeride, downhill, and a variety of track and slalom types. Each of these place different demands on the bike, requiring different designs for optimal performance. MTB development has led to an increase in suspension travel, now often up to 8 inches (200 mm), and gearing up to 27 speeds, to facilitate both climbing and rapid descents. Advancements in gearing have also led to a "1x" (pronounced "one-by") trend, simplifying the gearing to one chainring in the front and a cassette at the rear, typically with 9 to 12 sprockets.
The expressions "all terrain bicycle", "all terrain bike", and the acronym "ATB" are used as synonyms for "mountain bike", but some authors consider them passé.Mountain biking
Mountain biking is a sport of riding bicycles off-road, often over rough terrain, using specially designed mountain bikes. Mountain bikes share similarities with other bikes but incorporate features designed to enhance durability and performance in rough terrain. Mountain biking can generally be broken down into multiple categories: cross country, trail riding, all mountain (also referred to as "Enduro"), downhill, freeride and dirt jumping.
This sport requires endurance, core strength and balance, bike handling skills, and self-reliance. Advanced riders pursue both steep technical descents and high incline climbs. In the case of freeride, downhill, and dirt jumping, aerial maneuvers are performed off both natural features and specially constructed jumps and ramps.
Mountain bikers ride on off-road trails such as singletrack, back-country roads, wider bike park trails, fire roads, and some advanced trails are designed with jumps, berms, and drop-off to add excitement to the trail. Riders with enduro and downhill bikes will often visit ski resorts that stay open in the summer to ride downhill specific trails, using the ski lifts to return to the top with their bikes. Because riders are often far from civilization, there is a strong ethic of self-reliance in the sport. Riders learn to repair broken bikes and flat tires to avoid being stranded. Many riders carry a backpack, including water, food, tools for trailside repairs, and a first aid kit in case of injury. Group rides are common, especially on longer treks. Mountain bike orienteering adds the skill of map navigation to mountain biking.Mountaineering
Mountaineering is the set of activities that involves ascending mountains. Mountaineering-related activities include traditional outdoor climbing, skiing, and traversing via ferratas. Indoor climbing, sport climbing and bouldering are also considered mountaineering by some.
Unlike most sports, mountaineering lacks widely-applied formal rules, regulations, and governance; mountaineers adhere to a large variety of techniques and philosophies when climbing mountains. Numerous local alpine clubs support mountaineers by hosting resources and social activities. A federation of alpine clubs, the International Climbing and Mountaineering Federation (UIAA), is the International Olympic Committee-recognized world organization for mountaineering and climbing.Swiss cheese features
Swiss cheese features (SCFs) are curious pits in the south polar ice cap of Mars (Mare Australe quadrangle) named from their similarity to the holes in Swiss cheese. They were first seen in 2000 using Mars Orbiter Camera imagery. They are typically a few hundred meters across and 8 metres deep, with a flat base and steep sides. They tend to have similar bean-like shapes with a cusp pointing towards the south pole, indicating that insolation is involved in their formation. The angle of the Sun probably contributes to their roundness. Near the Martian summer solstice, the Sun can remain continuously just above the horizon; as a result the walls of a round depression will receive more intense sunlight, and sublimate much more rapidly than the floor. The walls sublimate and recede, while the floor remains the same.
As the seasonal frost disappears, the pit walls appear to darken considerably relative to the surrounding terrain. The SCFs have been observed to grow in size, year by year, at an average rate of 1 to 3 meters, suggesting that they are formed in a thin layer (8m) of carbon dioxide ice lying on top of water ice. Later research with HiRISE showed that the pits are in a 1-10 meter thick layer of dry ice that is sitting on a much larger water ice cap. Pits have been observed to begin with small areas along faint fractures. The circular pits have steep walls that work to focus sunlight, thereby increasing erosion. For a pit to develop, a steep wall of about 10 cm and a length of over 5 meters is necessary.Terrain softening
The landscape polewards of around 30 degrees latitude on Mars has a distinctively different appearance to that nearer the equator, and is said to have undergone terrain softening. Softened terrain lacks the sharp ridge crests seen near the equator, and is instead smoothly rounded. This rounding is thought to be caused by high concentrations of water ice in soils. The term was coined in 1986 by Steve Squyres and Michael Carr from examining imagery from the Viking missions to Mars.
Below 30 degrees of latitude, impact craters have steep walls; well-defined, sharp rims; and flat or smoothly bowl-shaped floors. Ridges on intercrater plains come to similarly well-defined, pointed crests. However, above this latitude, these same features appear very different. The crests seen on ridges and crater rims appear strongly rounded and much more poorly defined. The relief (height) of features is somewhat reduced. Small craters are noticeably less common. In other words, terrain which elsewhere looked sharp here looks "soft". This texture has also been described as "smooth", or "rolling". Softened craters are also commonly infilled with concentric patterns on their floors.On Earth, diffusive creep of soils is associated with rounded hillslopes. Squyres and Carr thus attributed the softened texture to accelerated viscous creep in shallow soils near the surface, and went on to associate this accelerated creep with the presence of ground ice at these latitudes. This conclusion has been largely borne out by subsequent research. In the late 1980s some attempts were made to link terrain softening with dust and aeolian processes, though this hypothesis has largely been superseded by more recent observations.Terrain softening is one of a suite of features seen in the midlatitudes of Mars—also including lobate debris aprons, lineated valley fill, concentric crater fill, latitude dependent mantle, patterned ground, viscous flow features, arcuate ridges, recurring slope lineae, and gullies—whose form and distribution strongly suggest the abundance of ice at the surface.Urban warfare
Urban warfare is combat conducted in urban areas such as towns and cities. Urban combat is very different from combat in the open at both the operational and tactical level. Complicating factors in urban warfare include the presence of civilians and the complexity of the urban terrain. Urban combat operations may be conducted in order to capitalize on the strategic or tactical advantages with which possession or control of a particular urban area gives or to deny these advantages to the enemy.Fighting in urban areas negates the advantages that one side may have over the other in armour, heavy artillery, or air support. Ambushes laid down by small groups of soldiers with handheld anti-tank weapons can effectively destroy entire columns of modern armour (as in the First Battle of Grozny), while artillery and air support can be severely reduced if the 'superior' party wants to limit civilian casualties as much as possible, but the defending party does not (or even uses civilians as human shields).
Some civilians may be difficult to distinguish from combatants such as armed militias and gangs, and particularly individuals who are simply trying to protect their homes from attackers. Tactics are complicated by a three-dimensional environment, limited fields of view and fire because of buildings, enhanced concealment and cover for defenders, below-ground infrastructure, and the ease of placement of booby traps and snipers.Walker (Star Wars)
All Terrain Walkers are armoured fighting vehicles from the Star Wars universe that traverse the landscape on mechanical legs. They are used by the Old Republic, the Galactic Empire, and the First Order for ground assault, reconnaissance or transport. Throughout the saga walkers have played a pivotal role in the fate of characters and the outcome of battles. Industrial Light and Magic (ILM) is responsible for their animation and design, often using models, stop-motion animation, and relevant matte paintings to depict their presence in the films.
There are a variety of walkers: The Empire Strikes Back introduces the All Terrain Armored Transport (AT-AT) and All Terrain Scout Transport (AT-ST). Star Wars: Episode II – Attack of the Clones, Star Wars: Episode III – Revenge of the Sith and The Clone Wars introduced earlier models of walkers, such as the All-Terrain Tactical Enforcer (AT-TE), and the All Terrain Recon Transports (AT-RT). The Star Wars expanded universe features numerous walker variants have been merchandised in popular culture.