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Compass rose

For the meteorological graphic, see Wind rose A common compass rose as found on a nautical chart showing both true north and magnetic north with magnetic variation. Also notice the correspondence between the thirty-two point rose (inner circle) and the modern 0-360° graduations. A compass rose, sometimes called a windrose, or Rose of the Winds, is a figure on a compass, map, nautical chart, or monument used to display the orientation of the cardinal directions: North, East, South, and West—and their intermediate points. It is also the term for the graduated markings found on the traditional magnetic compass. Today, the idea of a compass rose is found on, or featured in, almost all navigation systems, including nautical charts, non-directional beacons (NDB), VHF omnidirectional range (VOR) systems, global-positioning systems (GPS), and similar equipment. Compass rose with the eight principal winds The modern compass rose has eight principal winds. Listed clockwise, these are: Although modern compasses use the names of the eight principal directions (N, NE, E, SE, etc.), older compasses use the traditional Italianate wind names of Medieval origin (Tramontana, Greco, Levante, etc.) 4-point compass roses use only the four "basic winds" or "cardinal directions" (North, East, South, West), with angles of difference at 90°. 8-point compass roses us the eight principal winds—that is, the four cardinal directions (N, E, S, W) plus the four "intercardinal" or "ordinal directions" (NE, SE, SW, NW), at angles of difference of 45°. 16-point compass roses are constructed by bisecting the angles of the principal winds to come up with intermediate compass points, known as half-winds, at angles of difference of 221⁄2°. The names of the half-winds are simply combinations of the principal winds to either side, principal then ordinal. E.g. North-northeast (NNE), East-northeast (ENE), etc. 32-point compass roses are constructed by bisecting these angles, and coming up with quarter-winds at 111⁄4° angles of difference. Quarter-wind names are constructed with the names "X by Y", which can be read as "one quarter wind from X toward Y", where X is one of the eight principal winds and Y is one of the two adjacent cardinal directions. E.g. North-by-east (NbE) is one quarter wind from North towards East, Northeast-by-north (NEbN) is one quarter wind from Northeast toward North. Naming all 32 points on the rose is called "boxing the compass". The 32-point rose has the uncomfortable number of 111⁄4° between points, but is easily found by halving divisions and may have been easier for those not using a 360° circle. Using gradians, of which there are 400 in a circle, the sixteen-point rose will have twenty-five gradians per point. A 4-point compass rose An 8-point compass rose A 16-point compass rose A 32-point compass rose More details Android, Windows

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Benchmark

This article is about the use of bench marks in surveying. For other uses, see Benchmark. An Ordnance Survey cut mark in the UK The term bench mark, or benchmark, originates from the chiseled horizontal marks that surveyors made in stone structures, into which an angle-iron could be placed to form a "bench" for a leveling rod, thus ensuring that a leveling rod could be accurately repositioned in the same place in the future. These marks were usually indicated with a chiseled arrow below the horizontal line. The term is generally applied to any item used to mark a point as an elevation reference. Frequently, bronze or aluminum disks are set in stone or concrete, or on rods driven deeply into the earth to provide a stable elevation point. If an elevation is marked on a map, but there is no physical mark on the ground, it is a spot height. The height of a benchmark is calculated relative to the heights of nearby benchmarks in a network extending from a fundamental benchmark. A fundamental benchmark is a point with a precisely known relationship to the level datum of the area, typically mean sea level. The position and height of each benchmark is shown on large-scale maps. The terms "height" and "elevation" are often used interchangeably, but in many jurisdictions they have specific meanings; "height" commonly refers to a local or relative difference in the vertical (such as the height of a building), whereas "elevation" refers to the difference from a nominated reference surface (such as sea-level, or a mathematical/geodetic model that approximates the sea level known as the geoid). Elevation may be specified as normal height (above a reference ellipsoid), orthometric height, or dynamic height which have slightly different definitions. More details Android, Windows

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Terrain

Not to be confused with Terrane. For the fruit, see Terret gris. For the store, see Urban Outfitters. Present-day Earth altimetry and bathymetry. Data from the National Geophysical Data Center's TerrainBase Digital Terrain Model. Relief map of Sierra Nevada A shaded and colored image (i.e. terrain is enhanced) of varied terrain from the Shuttle Radar Topography Mission. This shows elevation model of New Zealand's Alpine Fault running about 500 km (300 mi) long. The escarpment is flanked by a vast chain of hills between the fault and the mountains of New Zealand's Southern Alps. Northeast is towards the top. Terrain or relief (also topographical relief) is the vertical and horizontal dimension of the land surface. When relief is described underwater, the term bathymetry is used. The Latin Word "Terra (The root word of terrain)," is "Earth." Terrain is used as a general term in physical geography, referring to 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. More details Android, Windows

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Region

This article is about the concept of region in geography. For other uses, see Region (disambiguation). In geography, regions are areas broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and the interaction of humanity and the environment (environmental geography). Geographic regions and sub-regions are mostly described by their imprecisely defined, and sometimes transitory boundaries, except in human geography, where jurisdiction areas such as national borders are defined in law. Apart from the global continental regions, there are also hydrospheric and atmospheric regions that cover the oceans, and discrete climates above the land and water masses of the planet. The land and water global regions are divided into subregions geographically bounded by large geological features that influence large-scale ecologies, such as plains and features. As a way of describing spatial areas, the concept of regions is important and widely used among the many branches of geography, each of which can describe areas in regional terms. For example, ecoregion is a term used in environmental geography, cultural region in cultural geography, bioregion in biogeography, and so on. The field of geography that studies regions themselves is called regional geography. In the fields of physical geography, ecology, biogeography, zoogeography, and environmental geography, regions tend to be based on natural features such as ecosystems or biotopes, biomes, drainage basins, natural regions, mountain ranges, soil types. Where human geography is concerned, the regions and subregions are described by the discipline of ethnography. A region has its own nature that could not be moved. The first nature is its natural environment (landform, climate, etc.). The second nature is its physical elements complex that were built by people in the past. The third nature is its socio-cultural context that could not be replaced by new immigrants.[citation needed] More details Android, Windows

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Natural resource

"Primary resource" redirects here. For original sources used in research, see Primary source. The rainforest in Fatu-Hiva, in the Marquesas Islands, is an example of an undisturbed natural resource. Forest provides timber for humans, food and shelter for the flora and fauna. The nutrient cycle between organisms form food chains and biodiversity of species. The Carson Fall in Mount Kinabalu, Malaysia is an example of undisturbed natural resource. Waterfalls provide spring water for humans, animals and plants for survival and also habitat for marine organisms. The water current can be used to turn turbines for hydroelectric generation. The ocean is an example of a natural resource. Ocean waves can be used to generate wave power which is a renewable energy. Ocean water is important for salt production, desalination, and providing habitat for deep water fishes. There are biodiversity of marine species in the sea where nutrient cycles are common. A picture of the Udachnaya pipe, an open-pit diamond mine in Siberia. An example of a non-renewable natural resource. Natural resources are resources that exist without the actions of humankind. This includes all valued characteristics such as magnetic, gravitational, and electrical properties and forces. On earth it includes; sunlight, atmosphere, water, land, air (includes all minerals) along with all vegetation and animal life that naturally subsists upon or within the heretofore identified characteristics and substances. Particular areas such as the rainforest in Fatu-Hiva are often characterized by the biodiversity and geodiversity existent in their ecosystems. Natural resources may be further classified in different ways. Natural resources are materials and components (something that can be used) that can be found within the environment. Every man-made product is composed of natural resources (at its fundamental level). A natural resource may exist as a separate entity such as fresh water, and air, as well as a living organism such as a fish, or it may exist in an alternate form which must be processed to obtain the resource such as metal ores, petroleum, and most forms of energy. There is much debate worldwide over natural resource allocations, this is particularly true during periods of increasing scarcity and shortages (depletion and overconsumption of resources) but also because the exportation of natural resources is the basis for many economies (particularly for developed countries). Some natural resources such as sunlight and air can be found everywhere, and are known as ubiquitous resources. However, most resources only occur in small sporadic areas, and are referred to as localized resources. There are very few resources that are considered inexhaustible (will not run out in foreseeable future) – these are solar radiation, geothermal energy, and air (though access to clean air may not be). The vast majority of resources are theoretically exhaustible, which means they have a finite quantity and can be depleted if managed improperly. More details Android, Windows

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Polar circle

For the ship of this name, see HMS Endurance. For the concept in geometry, see Polar circle (geometry). The polar circle in Finland, 1975. The polar circle in Norway at Saltfjellet mountain plateau. Relationship between Earth's axial tilt (ε) to the tropical and polar circles A polar circle is either the Arctic Circle or the Antarctic Circle. On Earth, the Arctic Circle is located at a latitude of 66°33′46.4″ N, and the Antarctic Circle is located at a latitude of 66°33′46.4″ S. Areas between each polar circle and its associated pole (North Pole or South Pole), known geographically as the frigid zones, would theoretically experience at least one 24-hour period when the sun is continuously above the horizon and at least one 24-hour period when the sun is continuously below the horizon annually. However, due to atmospheric refraction and the Sun being an extended object rather than a point source, the continuous daylight area is somewhat extended while the continuous darkness area is somewhat reduced. The latitude of the polar circles is 90 degrees minus the axial tilt of the Earth's axis of daily rotation relative to the ecliptic, the plane of the Earth's orbit. This tilt varies slightly, a phenomenon described as nutation. Therefore, the latitudes noted above are calculated by averaging values of tilt observed over many years. The axial tilt also exhibits long-term variations as described in the reference article (a difference of 1 second of arc in the tilt is equivalent to change of about 31 metres north or south in the positions of the polar circles on the Earth's surface). More details Android, Windows

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Midnight sun

For other uses, see Midnight sun (disambiguation). The Altafjord in Alta, Norway, bathed in the midnight sun. The midnight sun is a natural phenomenon that occurs in the summer months in places north of the Arctic Circle or south of the Antarctic Circle, when the sun remains visible at the local midnight. Around the summer solstice (approximately 21 June in the Northern Hemisphere and 22 December in the Southern Hemisphere) the sun is visible for the full 24 hours, given fair weather. The number of days per year with potential midnight sun increases the farther towards either pole one goes. Although approximately defined by the polar circles, in practice the midnight sun can be seen as much as 55 miles (90 km) outside the polar circle, as described below, and the exact latitudes of the farthest reaches of midnight sun depend on topography and vary slightly year-to-year. There are no permanent, economically autonomous human settlements south of the Antarctic Circle, only research stations, so the countries and territories whose populations experience the midnight sun are limited to those crossed by the Arctic Circle: Canada (Yukon, Northwest Territories, and Nunavut), Greenland, Iceland, Finland, Norway, Russia, Sweden, and the United States (Alaska). A quarter of Finland's territory lies north of the Arctic Circle, and at the country's northernmost point the sun does not set at all for 60 days during summer. In Svalbard, Norway, the northernmost inhabited region of Europe, there is no sunset from approximately 19 April to 23 August. The extreme sites are the poles, where the sun can be continuously visible for half the year. The opposite phenomenon, polar night, occurs in winter, when the sun stays below the horizon throughout the day. Since the axial tilt of the Earth is considerable (approximately 23 degrees 27 minutes), the sun does not set at high latitudes in local summer. The duration of sunlight increases from one day during the summer solstice at the polar circle, to several weeks only 100 km closer to the pole, to six months at the poles. At extreme latitudes, the midnight sun is usually referred to as polar day. At the poles themselves, the sun rises and sets only once each year. During the six months that the sun is above the horizon, it spends the days continuously moving in circles around the observer, gradually spiralling higher and reaching its highest circuit of the sky at the summer solstice. Because of atmospheric refraction, and also because the sun is a disk rather than a point, the midnight sun may be experienced at latitudes slightly below the polar circle, though not exceeding one degree (depending on local conditions). For example, Iceland is known for its midnight sun, even though most of it (Grímsey is the exception) is slightly south of the Arctic Circle. For the same reasons, the period of sunlight at the poles is slightly longer than six months. Even the northern extremities of Scotland (and places at similar latitudes, such as St. Petersburg) experience twilight in the northern sky at around the summer solstice. Observers at heights appreciably above sea level can experience extended periods of midnight sun as a result of the "dip" of the horizon viewed from altitude. More details Android, Windows

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Polar regions of Earth

Play media Visualization of the ice and snow covering Earth's north and south polar regions Northern Hemisphere permafrost (permanently frozen ground) in purple The polar regions of Earth, also known as Earth's frigid zones, are the regions of Earth surrounding its geographical poles (the North and South Poles). These regions are dominated by Earth's polar ice caps, the northern resting on the Arctic Ocean and the southern on the continent of Antarctica. More details Android, Windows

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Polar ice cap

This article is about polar ice caps in general. For Earth's ice cap, see Arctic ice pack. "Polar ice" redirects here. For the vodka, see Polar Ice (vodka). Polar ice cap on Mars, seen by the Hubble Telescope A polar ice cap or polar cap is a high-latitude region of a planet, dwarf planet, or natural satellite that is covered in ice. There are no requirements with respect to size or composition for a body of ice to be termed a polar ice cap, nor any geological requirement for it to be over land; only that it must be a body of solid phase matter in the polar region. This causes the term "polar ice cap" to be something of a misnomer, as the term ice cap itself is applied more narrowly to bodies that are over land, and cover less than 50,000 km²: larger bodies are referred to as ice sheets. The composition of the ice will vary. For example, Earth's polar caps are mainly water ice, whereas Mars's polar ice caps are a mixture of solid carbon dioxide and water ice. Polar ice caps form because high-latitude regions receive less energy in the form of solar radiation from the Sun than equatorial regions, resulting in lower surface temperatures. Earth's polar caps have changed dramatically over the last 12,000 years. Seasonal variations of the ice caps takes place due to varied solar energy absorption as the planet or moon revolves around the Sun. Additionally, in geologic time scales, the ice caps may grow or shrink due to climate variation. More details Android, Windows

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Glade

A glade in a montane forest in the Olympic Mountains An alder glade along the Elwha River In the most general sense, a glade or clearing is an open area within a woodland. Glades are often grassy meadows under the canopy of deciduous trees such as red alder or quaking aspen in western North America. They also represent openings in forests where local conditions such as avalanches, poor soils, or fire damage have created semi-permanent clearings. They are very important to herbivorous animals, such as deer and elk, for forage and denning activities. Sometimes the word is used in a looser sense, as in the treeless wetlands of the Everglades. In the central United States, the term glade is used more specifically to describe rocky, prairie-like habitats that occur in areas of shallow soil. Glades are characterized by unique plant and animal communities that are adapted to harsh and dry conditions. More details Android, Windows

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Polder

For other uses, see Polder (disambiguation). Polder at Neßmersiel, Germany, aerial view in May 2012 Satellite image of Noordoostpolder, Netherlands (595.41 km²) A polder (Dutch pronunciation: [pɔldər]) is a low-lying tract of land enclosed by dikes that forms an artificial hydrological entity, meaning it has no connection with outside water other than through manually operated devices. There are three types of polder: Land reclaimed from a body of water, such as a lake or the sea bed Flood plains separated from the sea or river by a dike Marshes separated from the surrounding water by a dike and subsequently drained The ground level in drained marshes subsides over time. All polders will eventually be below the surrounding water level some or all of the time. Water enters the low-lying polder through infiltration and water pressure of ground water, or rainfall, or transport of water by rivers and canals. This usually means that the polder has an excess of water, which is pumped out or drained by opening sluices at low tide. Care must be taken not to set the internal water level too low. Polder land made up of peat (former marshland) will sink in relation to its previous level, because of peat decomposing when exposed to oxygen from the air. Polders are at risk from flooding at all times, and care must be taken to protect the surrounding dikes. Dikes are typically built with locally available materials, and each material has its own risks: sand is prone to collapse owing to saturation by water; dry peat is lighter than water and potentially unable to retain water in very dry seasons. Some animals dig tunnels in the barrier, allowing water to infiltrate the structure; the muskrat is known for this activity and actively hunted in certain European countries because of it. Polders are most commonly, though not exclusively, found in river deltas, former fenlands and coastal areas. Flooding of polders has also been used as a military tactic in the past. One example is the flooding of the polders along the Yser river during World War I. Opening the sluices at high tide and closing them at low tide turned the polders into an inaccessible swamp, which allowed the Allied armies to stop the German army. More details Android, Windows

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Water hemisphere

Redirect to: Land and water hemispheres From a merge: This is a redirect from a page that was merged into another page. This redirect was kept in order to preserve this page's edit history after its content was merged into the target page's content. Please do not remove the tag that generates this text (unless the need to recreate content on this page has been demonstrated) nor delete this page. For redirects with substantive page histories that did not result from page merges use {{R with history}} instead. More details Android, Windows

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List of peninsulas

"Peninsular" redirects here. For the Spanish caste, see Peninsulars. For other uses, see Peninsula (disambiguation). The world's largest peninsula, the Arabian Peninsula Baja California Peninsula, Mexico Presented below is a list of peninsulas. A peninsula (Latin: paeninsula from paene "almost" and insula "island") is a piece of land that is bordered by water on three sides but connected to mainland. The surrounding water is usually understood to be continuous, though not necessarily named as such. A peninsula can also be a headland, cape, island promontory, bill, point, or spit. A point is generally considered a tapering piece of land projecting into a body of water that is less prominent than a cape. In English, the plural of peninsula is peninsulas or, less commonly, peninsulae. A river which courses through a very tight meander is also sometimes said to form a "peninsula" within the (almost closed) loop of water. More details Android, Windows

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Population density

Population density (people per km2) by country, 2015 Population density (people per km2) by country, 2006 Population density (people per km2) map of the world in 1994. In relation to the equator it is seen that the vast majority of the human population lives in the Northern Hemisphere. Population density (people per km2) map of the world in 1994 Deserts around the world. Compare with maps above. See also this image for location of densely populated areas (cities) in various vegetation zones. Population density (in agriculture: standing stock and standing crop) is a measurement of population per unit area or unit volume; it is a quantity of type number density. It is frequently applied to living organisms, and most of the time to humans. It's a key geographical term. More details Android, Windows

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Active layer

For other uses, see Layer (electronics). The red dotted-to-solid line depicts the average temperature profile with depth of soil in a permafrost region. The trumpet-shaped lines at the top show seasonal maximum and minimum temperatures in the "active layer", which commences at the depth where the maximum annual temperature intersects 0° C. The active layer is seasonally frozen. The middle zone is permanently frozen as "permafrost". And the bottom layer is where the geothermal temperature is above freezing. Note the importance of the vertical 0° C line: It denotes the bottom of the active layer in the seasonally variable temperature zone and the bottom limit of permafrost as the temperature increases with depth. In environments containing permafrost, the active layer is the top layer of soil that thaws during the summer and freezes again during the autumn. In all climates, whether they contain permafrost or not, the temperature in the lower levels of the soil will remain more stable than that at the surface, where the influence of the ambient temperature is greatest. This means that, over many years, the influence of cooling in winter and heating in summer (in temperate climates) will decrease as depth increases.[1] If the winter temperature is below the freezing point of water, a frost front will form in the soil. This "frost front" is the boundary between frozen and unfrozen soil, and with the coming of spring and summer, the soil is thawed, always from the top down. If the heating during summer exceeds the cooling during winter, the soil will be completely thawed during the summer and there will be no permafrost. This occurs when the mean annual temperature is above 0°C (32°F), but also occurs when the mean annual temperature is slightly below 0°C on sites exposed to the sun with coarse-textured parent materials (vegetation). When there is not sufficient heat to thaw the frozen soil completely, permafrost forms. The active layer in this environment consists of the top layers of soil which thaws during the summer, while the inactive layer refers to the soil below which is frozen year-round because the heat fails to penetrate. Liquid water cannot flow below the active layer, with the result that permafrost environments tend to be very poorly drained and boggy. More details Android, Windows

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Whitewater

For other uses, see Whitewater (disambiguation). Whitewater on the river Guil (French Alps) Whitewater on the small rapid of Kannonkoski, Central Finland Vivid water of the Torne River between Sweden and Finland. Whitewater, usually spelled white water in both American and British English, is formed in a rapid, when a river's gradient increases enough to create so much turbulence that air is entrained into the water body, that is, it forms a bubbly or aerated and unstable current; the frothy water appears white. The term is also loosely used to refer to less turbulent, but still agitated, flows.[citation needed] The term "whitewater" also has a broader meaning, applying to any river or creek itself that has a significant number of rapids. The term is also used as an adjective describing boating on such rivers, such as whitewater canoeing or whitewater kayaking. More details Android, Windows

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Circle of latitude

Mercator projection world map, true angles but untrue regarding areas, especially at high latitudes. Also note increasing distances between the latitudes towards the poles and the parallel longitude lines. The only true world maps are globes. The Mercator projection comes from a globe inside a cylinder. Picture shows projection and use of a worldwide Mercator projection map. The Mercator projection first came in use by the Dutch in the 16th century A circle of latitude on the Earth is an imaginary east–west circle connecting all locations (ignoring elevation) with a given latitude. A location's position along a circle of latitude is given by its longitude. Circles of latitude are often called parallels because they are parallel to each other – that is, any two circles are always the same distance apart. Unlike circles of longitude, which all are great circles with the centre of Earth in the middle, the circles of latitude get smaller as the distance from the Equator increases. Their length can be calculated by a common sine or cosine function. The 60th circle of latitude is half as long as the equator (disregarding Earth's minor flattening, which is less than 0.3%). A circle of latitude is perpendicular to all meridians. The latitude of the circle is approximately the angle between the equator and the circle, with the angle's vertex at the Earth's centre. The equator is at 0°, and the North and South poles are at 90° north and 90° south respectively. The Equator is the longest circle of latitude and is the only circle of latitude which also is a great circle. There are 89 integral (whole degree) circles of latitude between the equator and the Poles in each hemisphere, but these can be divided into more precise measurements of latitude, and are often represented as a decimal degree (e.g. 34.637°N) or with minutes and seconds (e.g. 22°14'26"S). There is no limit to how precisely latitude can be measured, and so there are an infinite number of circles of latitude on Earth. On a map, the circles of latitude may or may not be parallel, and their spacing may vary, depending on which projection is used to map the surface of the Earth onto a plane. On an equirectangular projection, centered on the equator, the circles of latitude are horizontal, parallel, and equally spaced. On other cylindrical and pseudocylindrical projections, the circles of latitude are horizontal and parallel, but may be spaced unevenly to give the map useful characteristics. For instance, on a Mercator projection the circles of latitude are more widely spaced near the poles to preserve local scales and shapes, while on a Gall–Peters projection the circles of latitude are spaced more closely near the poles so that comparisons of area will be accurate. On most non-cylindrical and non-pseudocylindrical projections, the circles of latitude are neither straight nor parallel. Arcs of circles of latitude are sometimes used as boundaries between countries or regions where distinctive natural borders are lacking (such as in deserts), or when an artificial border is drawn as a "line on a map", which was made in massive scale during the 1884 Berlin Conference, regarding huge parts of the African continent. North American nations and states have also mostly been created by straight lines, which are often parts of circles of latitudes. For instance, the northern border of Colorado is at 41°N while the southern border is at 37°N. Roughly half the length of border between the United States and Canada follows 49°N. More details Android, Windows