The People's Liberation Organisation of Tamil Eelam (PLOTE) is a former Tamil militant group that had become a pro-government paramilitary group and political party. PLOTE's political wing is known as the Democratic People's Liberation Front .
117-729: PLOTE was founded in 1980 by an ex- surveyor Uma Maheswaran alias Mukundan, who became its general secretary . He was the chairman of the Liberation Tigers of Tamil Eelam (Tamil Tigers or LTTE) from 1977 to 1980. He was trained in Lebanon and later in Syria under the Palestinian nationalist organization Popular Front for the Liberation of Palestine . After a bitter rivalry with Velupillai Prabhakaran , Uma Maheswaran left
234-465: A cave . They have been important to humans as a place of shelter since the dawn of humanity. Craters are depressions in the ground, but unlike caves, they do not provide shelter or extend underground . There are many kinds of craters, such as impact craters , volcanic calderas , and isostatic depressions . Karst processes can create both solution caves , the most frequent cave type, and craters, as seen in karst sinkholes . The pedosphere
351-434: A habitat refers to the environment where a given species or population of organisms lives. Biomes may span more than one continent, and contain a variety of ecosystems and habitats. Land plants evolved from green algae , and are called embryophytes . They include trees , shrubs , ferns , grass , moss , and flowers . Most plants are vascular plants , meaning that their tissues distribute water and minerals throughout
468-495: A plane table in 1551, but it is thought that the instrument was in use earlier as his description is of a developed instrument. Gunter's chain was introduced in 1620 by English mathematician Edmund Gunter . It enabled plots of land to be accurately surveyed and plotted for legal and commercial purposes. Leonard Digges described a theodolite that measured horizontal angles in his book A geometric practice named Pantometria (1571). Joshua Habermel ( Erasmus Habermehl ) created
585-445: A GPS on large scale surveys makes them popular for major infrastructure or data gathering projects. One-person robotic-guided total stations allow surveyors to measure without extra workers to aim the telescope or record data. A fast but expensive way to measure large areas is with a helicopter, using a GPS to record the location of the helicopter and a laser scanner to measure the ground. To increase precision, surveyors place beacons on
702-623: A coastline may be impacted by the tides , caused by changes in gravitational forces on larger bodies of water. Coasts are important zones in natural ecosystems, often home to a wide range of biodiversity . On land, they harbour important ecosystems such as freshwater or estuarine wetlands , which are important for bird populations and other terrestrial animals. In wave-protected areas they harbor saltmarshes , mangroves or seagrasses , all of which can provide nursery habitat for finfish, shellfish , and other aquatic species. Rocky shores are usually found along exposed coasts and provide habitat for
819-477: A fixed base station and a second roving antenna. The position of the roving antenna can be tracked. The theodolite , total station and RTK GPS survey remain the primary methods in use. Remote sensing and satellite imagery continue to improve and become cheaper, allowing more commonplace use. Prominent new technologies include three-dimensional (3D) scanning and lidar -based topographical surveys. UAV technology along with photogrammetric image processing
936-423: A great step forward in the instrument's accuracy. William Gascoigne invented an instrument that used a telescope with an installed crosshair as a target device, in 1640. James Watt developed an optical meter for the measuring of distance in 1771; it measured the parallactic angle from which the distance to a point could be deduced. Dutch mathematician Willebrord Snellius (a.k.a. Snel van Royen) introduced
1053-592: A habitat for soil organisms , a recycling system for nutrients and organic wastes , a regulator of water quality , a modifier of atmospheric composition , and a medium for plant growth , making it a critically important provider of ecosystem services . Since soil has a tremendous range of available niches and habitats , it contains a prominent part of the Earth's genetic diversity . A gram of soil can contain billions of organisms, belonging to thousands of species, mostly microbial and largely still unexplored. Soil
1170-450: A height above sea level. As the surveying profession grew it created Cartesian coordinate systems to simplify the mathematics for surveys over small parts of the Earth. The simplest coordinate systems assume that the Earth is flat and measure from an arbitrary point, known as a 'datum' (singular form of data). The coordinate system allows easy calculation of the distances and direction between objects over small areas. Large areas distort due to
1287-433: A known size. It was sometimes used before to the invention of EDM where rough ground made chain measurement impractical. Historically, horizontal angles were measured by using a compass to provide a magnetic bearing or azimuth. Later, more precise scribed discs improved angular resolution. Mounting telescopes with reticles atop the disc allowed more precise sighting (see theodolite ). Levels and calibrated circles allowed
SECTION 10
#17327648667301404-455: A large area, it can influence climate and weather patterns. The terrain of a region largely determines its suitability for human settlement: flatter alluvial plains tend to have better farming soils than steeper, rockier uplands. Elevation is defined as the vertical distance between an object and sea level, while altitude is defined as the vertical distance from an object to Earth's surface. The elevation of Earth's land surface varies from
1521-491: A large elevation difference between the highest and lowest points would be deemed "high relief". Most land has relatively low relief. The change in elevation between two points of the terrain is called a slope or gradient. A topographic map is a form of terrain cartography which depicts terrain in terms of its elevation, slope, and the orientation of its landforms. It has prominent contour lines , which connect points of similar elevation, while perpendicular slope lines point in
1638-539: A long time to cause noticeable changes in the landscape—for example, the Grand Canyon was created over the past 70 million years by the Colorado River , which scientists estimate continues to erode the canyon at a rate of 0.3 meters (1 foot) every 200 years. However, humans have caused erosion to be 10–40 times faster than normal, causing half the topsoil of the surface of Earth's land to be lost within
1755-434: A loop pattern or link between two prior reference marks so the surveyor can check their measurements. Many surveys do not calculate positions on the surface of the Earth, but instead, measure the relative positions of objects. However, often the surveyed items need to be compared to outside data, such as boundary lines or previous survey's objects. The oldest way of describing a position is via latitude and longitude, and often
1872-618: A multi frequency phase shift of light waves to find a distance. These instruments eliminated the need for days or weeks of chain measurement by measuring between points kilometers apart in one go. Advances in electronics allowed miniaturization of EDM. In the 1970s the first instruments combining angle and distance measurement appeared, becoming known as total stations . Manufacturers added more equipment by degrees, bringing improvements in accuracy and speed of measurement. Major advances include tilt compensators, data recorders and on-board calculation programs. The first satellite positioning system
1989-411: A plan or map, and the points at the ends of the offset lines could be joined to show the feature. Traversing is a common method of surveying smaller areas. The surveyor starts from an old reference mark or known position and places a network of reference marks covering the survey area. They then measure bearings and distances between the reference marks, and to the target features. Most traverses form
2106-406: A point inside a triangle using the angles cast between the vertices at the unknown point. These could be measured more accurately than bearings of the vertices, which depended on a compass. His work established the idea of surveying a primary network of control points, and locating subsidiary points inside the primary network later. Between 1733 and 1740, Jacques Cassini and his son César undertook
2223-478: A profession. They established the basic measurements under which the Roman Empire was divided, such as a tax register of conquered lands (300 AD). Roman surveyors were known as Gromatici . In medieval Europe, beating the bounds maintained the boundaries of a village or parish. This was the practice of gathering a group of residents and walking around the parish or village to establish a communal memory of
2340-428: A reflector or prism to return the light pulses used for distance measurements. They are fully robotic, and can even e-mail point data to a remote computer and connect to satellite positioning systems , such as Global Positioning System . Real Time Kinematic GPS systems have significantly increased the speed of surveying, and they are now horizontally accurate to within 1 cm ± 1 ppm in real-time, while vertically it
2457-518: A role in the regional and global climate. Densely populated cities are warmer and create urban heat islands that have effects on the precipitation, cloud cover , and temperature of the region. A landform is a natural or manmade land feature. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography . Landforms include hills , mountains , canyons , and valleys , as well as shoreline features such as bays , capes , and peninsulas . The shoreline
SECTION 20
#17327648667302574-421: A set of practices called sustainable land management . A biome is an area "characterized by its vegetation, soil, climate, and wildlife ." There are five major types of biomes on land: grasslands, forests, deserts, tundras, and freshwater. Other types of biomes include shrublands, wetlands, and polar ice caps . An ecosystem refers to the interaction between organisms within a particular environment, and
2691-746: A solid phase of minerals and organic matter (the soil matrix), as well as a porous phase that holds gases (the soil atmosphere) and water (the soil solution). Accordingly, soil is a three- state system of solids, liquids, and gases. Soil is a product of several factors: the influence of climate , relief (elevation, orientation, and slope of terrain), organisms, and the soil's parent materials (original minerals) interacting over time. It continually undergoes development by way of numerous physical, chemical and biological processes, which include weathering and erosion . Given its complexity and strong internal connectedness , soil ecologists regard soil as an ecosystem . Soil acts as an engineering medium,
2808-476: A star is determined, the bearing can be transferred to a reference point on Earth. The point can then be used as a base for further observations. Survey-accurate astronomic positions were difficult to observe and calculate and so tended to be a base off which many other measurements were made. Since the advent of the GPS system, astronomic observations are rare as GPS allows adequate positions to be determined over most of
2925-455: A steady growth to the present-day forms or, more likely, a rapid growth early in Earth history followed by a long-term steady continental area. Continents are formed by plate tectonics , a process ultimately driven by the continuous loss of heat from the Earth's interior. On time scales lasting hundreds of millions of years, the supercontinents have formed and broken apart three times. Roughly 750 mya (million years ago), one of
3042-495: A theodolite with a compass and tripod in 1576. Johnathon Sission was the first to incorporate a telescope on a theodolite in 1725. In the 18th century, modern techniques and instruments for surveying began to be used. Jesse Ramsden introduced the first precision theodolite in 1787. It was an instrument for measuring angles in the horizontal and vertical planes. He created his great theodolite using an accurate dividing engine of his own design. Ramsden's theodolite represented
3159-593: A time component. Before EDM (Electronic Distance Measurement) laser devices, distances were measured using a variety of means. In pre-colonial America Natives would use the "bow shot" as a distance reference ("as far as an arrow can slung out of a bow", or "flights of a Cherokee long bow"). Europeans used chains with links of a known length such as a Gunter's chain , or measuring tapes made of steel or invar . To measure horizontal distances, these chains or tapes were pulled taut to reduce sagging and slack. The distance had to be adjusted for heat expansion. Attempts to hold
3276-433: A wide range of sessile animals (e.g. mussels , starfish , barnacles ) and various kinds of seaweeds . Along tropical coasts with clear, nutrient-poor water, coral reefs can often be found between depths of 1–50 meters (3.3–164.0 feet). According to a United Nations atlas, 44% of all people live within 150 km (93 mi) of the sea. Because of their importance in society and high concentration of population,
3393-442: Is a major component of the Earth's ecosystem. The world's ecosystems are impacted in far-reaching ways by the processes carried out in the soil, with effects ranging from ozone depletion and global warming to rainforest destruction and water pollution . With respect to Earth's carbon cycle , soil acts as an important carbon reservoir , and it is potentially one of the most reactive to human disturbance and climate change. As
3510-470: Is a reasonably sharp contrast between the more felsic upper continental crust and the lower continental crust, which is more mafic in character. The composition of land is not uniform across the Earth, varying between locations and between strata within the same location. The most prominent components of upper continental crust include silicon dioxide , aluminium oxide , and magnesium . The continental crust consists of lower density material such as
3627-474: Is a staple of contemporary land surveying. Typically, much if not all of the drafting and some of the designing for plans and plats of the surveyed property is done by the surveyor, and nearly everyone working in the area of drafting today (2021) utilizes CAD software and hardware both on PC, and more and more in newer generation data collectors in the field as well. Other computer platforms and tools commonly used today by surveyors are offered online by
People's Liberation Organisation of Tamil Eelam - Misplaced Pages Continue
3744-399: Is a term used when referring to moving the level to take an elevation shot from a different location. To "turn" the level, one must first take a reading and record the elevation of the point the rod is located on. While the rod is being kept in exactly the same location, the level is moved to a new location where the rod is still visible. A reading is taken from the new location of the level and
3861-400: Is also appearing. The main surveying instruments in use around the world are the theodolite , measuring tape , total station , 3D scanners , GPS / GNSS , level and rod . Most instruments screw onto a tripod when in use. Tape measures are often used for measurement of smaller distances. 3D scanners and various forms of aerial imagery are also used. The theodolite is an instrument for
3978-442: Is also used in wetland ecology, where "upland" plants indicate an area that is not a wetland. In addition, the term moorland refers to upland shrubland biomes with acidic soils, while heathlands are lowland shrublands with acidic soils. Geomorphology refers to the study of the natural processes that shape land's surface, creating landforms. Erosion and tectonics , volcanic eruptions , flooding , weathering , glaciation ,
4095-529: Is also used more generally, as in Persian rigestân ( ریگستان ) "place of sand, desert", golestân ( گلستان ) "place of flowers, garden", gurestân ( گورستان ) "graveyard, cemetery", and Hindustân ( هندوستان ) "land of the Indo people". The study of land and its history in general is called geography . Mineralogy is the study of minerals, and petrology is the study of rocks. Soil science
4212-488: Is an island , and a chain of islands is an archipelago . The smaller the island, the larger the percentage of its land area will be adjacent to the water, and subsequently will be coast or beach. Islands can be formed by a variety of processes. The Hawaiian islands , for example, even though they are not near a plate boundary, formed from isolated volcanic activity . Atolls are ring-shaped islands made of coral , created when subsidence causes an island to sink beneath
4329-412: Is an alternate method of determining the position of objects, and was often used to measure imprecise features such as riverbanks. The surveyor would mark and measure two known positions on the ground roughly parallel to the feature, and mark out a baseline between them. At regular intervals, a distance was measured at right angles from the first line to the feature. The measurements could then be plotted on
4446-505: Is because divergent conditions further away from the base reduce accuracy. Surveying instruments have characteristics that make them suitable for certain uses. Theodolites and levels are often used by constructors rather than surveyors in first world countries. The constructor can perform simple survey tasks using a relatively cheap instrument. Total stations are workhorses for many professional surveyors because they are versatile and reliable in all conditions. The productivity improvements from
4563-644: Is called the shoreline . The word land is derived from Old English , from the Proto-Germanic word * landą , "untilled land", and then the Proto-Indo-European * lendʰ- , especially in northern regions that were home to languages like Proto-Celtic and Proto-Slavic . Examples include Old Irish land , "land, plot, church building" and Old Irish ithlann , "threshing floor", and Old East Slavic ljadina "wasteland, weeds". A country or nation may be referred to as
4680-585: Is currently about half of that to within 2 cm ± 2 ppm. GPS surveying differs from other GPS uses in the equipment and methods used. Static GPS uses two receivers placed in position for a considerable length of time. The long span of time lets the receiver compare measurements as the satellites orbit. The changes as the satellites orbit also provide the measurement network with well conditioned geometry. This produces an accurate baseline that can be over 20 km long. RTK surveying uses one static antenna and one roving antenna. The static antenna tracks changes in
4797-619: Is functioning under the leadership of D. Siddarthan and is a pro-government minor political party that is alleged to cooperate with the Sri Lankan military against LTTE sympathizers. The group reportedly has around 1,500 permanent cadres in the north and east. In 2015 it was incorporated into the TNA. Some former members of the group also function along with the Sri Lankan Army as a para-military group in military activities against
People's Liberation Organisation of Tamil Eelam - Misplaced Pages Continue
4914-418: Is often defined as the solid, dry surface of Earth. The word land may also collectively refer the collective natural resources of Earth, including its land cover , rivers , shallow lakes , its biosphere , the lowest layer of the atmosphere ( troposphere ), groundwater reserves, and the physical results of human activity on land, such as architecture and agriculture. The boundary between land and sea
5031-459: Is pushed upwards, or subductional events, where Earth's crust is pushed into the mantle, causing the crust to melt, rise due to its low density, and solidify into hardened rock, thickening the crust. A plateau , also called a high plain or a tableland, is an area of a highland consisting of flat terrain that is raised sharply above the surrounding area on at least one side, creating steep cliffs or escarpments . Both volcanic activity such as
5148-448: Is the interface between the land and the ocean . It migrates each day as tides rise and fall, and moves over long periods of time as sea levels change. The shore extends from the low tide line to the highest elevation that can be reached by storm waves, and the coast stretches out inland until the point where ocean-related features are no longer found. When land is in contact with bodies of water, it can be eroded. The weathering of
5265-399: Is the outermost layer of Earth's continental surface and is composed of soil and subject to soil formation processes . Below it, the lithosphere encompasses both Earth's crust and the uppermost layer of the mantle . The lithosphere rests, or "floats", on top of the mantle below it via isostasy . Above the solid ground, the troposphere and humans' use of land can be considered layers of
5382-467: Is the study of soils, encompassing the sub-disciplines of pedology , which focuses on soil formation, and edaphology , which focuses on the relationship between soil and life. The earliest material found in the Solar System is dated to 4.5672 ± 0.0006 bya (billion years ago); therefore, the Earth itself must have been formed by accretion around this time. The formation and evolution of
5499-465: Is thicker than oceanic crust , and it is far more varied in terms of composition. About 31% of this continental crust is submerged in shallow water, forming continental shelves. Land provides many ecosystem services , such as mitigating climate change, regulating water supply through drainage basins and river systems, and supporting food production. Land resources are finite, which has led to regulations intended to safeguard these ecosystem services, and
5616-400: Is used in the planning and execution of most forms of construction . It is also used in transportation, communications, mapping, and the definition of legal boundaries for land ownership. It is an important tool for research in many other scientific disciplines. The International Federation of Surveyors defines the function of surveying as follows: A surveyor is a professional person with
5733-432: Is with an altimeter using air pressure to find the height. When more precise measurements are needed, means like precise levels (also known as differential leveling) are used. When precise leveling, a series of measurements between two points are taken using an instrument and a measuring rod. Differences in height between the measurements are added and subtracted in a series to get the net difference in elevation between
5850-689: The Earth's magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind . The atmosphere and oceans of the Earth continuously shape the land by eroding and transporting solids on the surface. Earth's crust formed when the molten outer layer of the planet Earth cooled to form a solid mass as the accumulated water vapour began to act in the atmosphere. Once land became capable of supporting life, biodiversity evolved over hundreds of millions of years, expanding continually except when punctuated by mass extinctions. The two models that explain land mass propose either
5967-509: The Principal Triangulation of Britain . The first Ramsden theodolite was built for this survey. The survey was finally completed in 1853. The Great Trigonometric Survey of India began in 1801. The Indian survey had an enormous scientific impact. It was responsible for one of the first accurate measurements of a section of an arc of longitude, and for measurements of the geodesic anomaly. It named and mapped Mount Everest and
SECTION 50
#17327648667306084-621: The Torrens system in South Australia in 1858. Torrens intended to simplify land transactions and provide reliable titles via a centralized register of land. The Torrens system was adopted in several other nations of the English-speaking world. Surveying became increasingly important with the arrival of railroads in the 1800s. Surveying was necessary so that railroads could plan technologically and financially viable routes. At
6201-799: The U.S. Federal Government and other governments' survey agencies, such as the National Geodetic Survey and the CORS network, to get automated corrections and conversions for collected GPS data, and the data coordinate systems themselves. Surveyors determine the position of objects by measuring angles and distances. The factors that can affect the accuracy of their observations are also measured. They then use this data to create vectors, bearings, coordinates, elevations, areas, volumes, plans and maps. Measurements are often split into horizontal and vertical components to simplify calculation. GPS and astronomic measurements also need measurement of
6318-523: The biosphere . Human manipulation of the land, including agriculture and architecture , can also be considered part of land. Land is formed from the continental crust , the layer of rock on which soil . groundwater , and human and animal activity sits. Though modern terrestrial plants and animals evolved from aquatic creatures, Earth's first cellular life likely originated on land. Survival on land relies on fresh water from rivers, streams, lakes, and glaciers, which constitute only three percent of
6435-515: The motherland , fatherland , or homeland of its people. Many countries and other places have names incorporating the suffix -land (e.g. England , Greenland , and New Zealand ). The equivalent suffix -stan from Indo-Iranian , ultimately derived from the Proto-Indo-Iranian * sthāna- , is also present in many country and location names, such as Pakistan , Afghanistan , and others throughout Central Asia . The suffix
6552-434: The upwelling of magma and extrusion of lava, or erosion of mountains caused from water, glaciers, or aeolian processes, can create plateaus. Plateaus are classified according to their surrounding environment as intermontane , piedmont , or continental . A few plateaus may have a small flat top while others are wider. Buttes are smaller, with less extrusive and more intrusive igneous rock, while plateaus or highlands are
6669-654: The whale , that evolved from terrestrial mammals back to an aquatic lifestyle. Many megafauna of the past, such as non-avian dinosaurs , have become extinct due to extinction events, e.g. the Quaternary extinction event . Land is "deeply intertwined with human development." It is a crucial resource for human survival, humans depend on land for subsistence, and can develop strong symbolic attachments to it. Access to land can determine "survival and wealth," particularly in developing countries, giving rise to complex power relationships in production and consumption. Most of
6786-432: The Earth's crust. About 30 percent of land has a dry climate, due to losing more water through evaporation than it gains from precipitation . Since warm air rises, this generates winds, though Earth's rotation and uneven sun distribution also play a part. Land is commonly defined as the solid, dry surface of Earth. It can also refer to the collective natural resources that the land holds, including rivers , lakes , and
6903-447: The Earth's curvature. North is often defined as true north at the datum. Land Land , also known as dry land , ground , or earth , is the solid terrestrial surface of Earth not submerged by the ocean or another body of water . It makes up 29.2% of Earth's surface and includes all continents and islands . Earth's land surface is almost entirely covered by regolith , a layer of rock , soil , and minerals that forms
7020-522: The Earth, and they are often used to establish maps and boundaries for ownership , locations, such as the designated positions of structural components for construction or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales. A professional in land surveying is called a land surveyor . Surveyors work with elements of geodesy , geometry , trigonometry , regression analysis , physics , engineering, metrology , programming languages , and
7137-585: The Egyptians' command of surveying. The groma instrument may have originated in Mesopotamia (early 1st millennium BC). The prehistoric monument at Stonehenge ( c. 2500 BC ) was set out by prehistoric surveyors using peg and rope geometry. The mathematician Liu Hui described ways of measuring distant objects in his work Haidao Suanjing or The Sea Island Mathematical Manual , published in 263 AD. The Romans recognized land surveying as
SECTION 60
#17327648667307254-811: The LTTE in 1980 and formed PLOTE. In late 1988, an attempted coup to overthrow the Maumoon Abdul Gayoom 's government in Maldives with the help of mercenaries from PLOTE was foiled with assistance from the Indian Army and Navy. There have been suggestions that the PLOTE may have been promised one of the small Maldivian islands as a base, possibly for arms shipments. In a recent interview, Vetrichelvan PLOTE's former representative in New Delhi claims it
7371-515: The LTTE. A prominent former PLOTE and later paramilitary leader Manika Dasan was killed by the LTTE in a claymore bomb attack in the town of Vavuniya . Another paramilitary leader from the Batticlao region, Plote Mohan, was killed by LTTE assassins in Colombo in 2004. Involvement in torture documented by Human Rights Watch in a number its reports including in 2008, 2009 2010 A letter to
7488-516: The PLOTE. In the mid-1970s, both Prabhakaran and Uma Maheswaran were members of the LTTE. During the gunfire, Jotheeswaran sustained bullet injuries both in his right and left thighs. Mukundan was also shot at but escaped unhurt. The accused V. Prabhakaran and Sivakumar were arrested and remanded . Both of them were proclaimed offenders of the Sri Lankan government with a reward on their head of Rs. 5 lakhs each. On May 25, 1982, Uma Maheswaran
7605-460: The Pope urged him to take up with the Sri Lankan government, the government's support of paramilitaries such as PLOTE. Surveying Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. These points are usually on the surface of
7722-628: The Solar System bodies occurred in tandem with the Sun. In theory, a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disc , out of which the planets then grow (in tandem with the star). A nebula contains gas, ice grains and dust (including primordial nuclides ). In nebular theory , planetesimals begin to form as particulate matter accumulates by cohesive clumping and then by gravity. The primordial Earth's assembly took 10– 20 myr . By 4.54 ± 0.04 bya ,
7839-561: The academic qualifications and technical expertise to conduct one, or more, of the following activities; Surveying has occurred since humans built the first large structures. In ancient Egypt , a rope stretcher would use simple geometry to re-establish boundaries after the annual floods of the Nile River . The almost perfect squareness and north–south orientation of the Great Pyramid of Giza , built c. 2700 BC , affirm
7956-438: The basis for dividing the western territories into sections to allow the sale of land. The PLSS divided states into township grids which were further divided into sections and fractions of sections. Napoleon Bonaparte founded continental Europe 's first cadastre in 1808. This gathered data on the number of parcels of land, their value, land usage, and names. This system soon spread around Europe. Robert Torrens introduced
8073-457: The bearing from every vertex in a figure, a surveyor can measure around the figure. The final observation will be between the two points first observed, except with a 180° difference. This is called a close . If the first and last bearings are different, this shows the error in the survey, called the angular misclose . The surveyor can use this information to prove that the work meets the expected standards. The simplest method for measuring height
8190-468: The beginning of the century, surveyors had improved the older chains and ropes, but they still faced the problem of accurate measurement of long distances. Trevor Lloyd Wadley developed the Tellurometer during the 1950s. It measures long distances using two microwave transmitter/receivers. During the late 1950s Geodimeter introduced electronic distance measurement (EDM) equipment. EDM units use
8307-528: The boundaries. Young boys were included to ensure the memory lasted as long as possible. In England, William the Conqueror commissioned the Domesday Book in 1086. It recorded the names of all the land owners, the area of land they owned, the quality of the land, and specific information of the area's content and inhabitants. It did not include maps showing exact locations. Abel Foullon described
8424-506: The climate change impacts on habitats and biodiversity, as well as natural resources, in the target areas. Land cover change detection and mapping is a key component of interdisciplinary land change science , which uses it to determine the consequences of land change on climate. Land change modeling is used to predict and analyze changes in land cover and use. Soil is a mixture of organic matter , minerals , gases , liquids , and organisms that together support life . Soil consists of
8541-636: The coast is important for major parts of the global food and economic system, and they provide many ecosystem services to humankind. For example, important human activities happen in port cities . Coastal fisheries for commercial, recreational, and subsistence purposes, and aquaculture are major economic activities and provide jobs, livelihoods, and protein for the majority of coastal human populations. Other coastal spaces like beaches and seaside resorts generate economic activity through tourism . Marine coastal ecosystems can also provide protection against sea level rise and tsunamis . In many countries,
8658-419: The coastal mangrove is the primary source of wood for fuel (e.g. charcoal) and building materials. Coastal ecosystems have a much higher capacity for carbon sequestration than many terrestrial ecosystems , and as such can play a critical role in the near future to help mitigate climate change effects by uptake of atmospheric anthropogenic carbon dioxide . A subcontinental area of land surrounded by water
8775-580: The direction of the steepest slope. Hypsometric tints are colors placed between contour lines to indicate elevation relative to sea level . A difference between uplands, or highlands , and lowlands is drawn in several earth science fields. In river ecology, " upland " rivers are fast-moving and colder than "lowland" rivers, encouraging different species of fish and other aquatic wildlife to live in these habitats. For example, nutrients are more present in slow-moving lowland rivers, encouraging different species of macrophytes to grow there. The term "upland"
8892-981: The earliest known supercontinents, Rodinia , began to break apart. The continents later recombined to form Pannotia , 600– 540 mya , then finally Pangaea , which also broke apart 180 mya . A continuous area of land surrounded by an ocean is called a landmass. Although it is most often written as one word to distinguish it from the usage "land mass"—the measure of land area—it may also be written as two words. There are four major continuous landmasses on Earth: Afro-Eurasia , America (landmass) , Antarctica , and Australia (landmass) , which are subdivided into continents. Up to seven geographical regions are commonly regarded as continents. Ordered from greatest to least land area, these continents are Asia , Africa , North America , South America , Antarctica , Europe , and Australia . Terrain refers to an area of land and its features. Terrain affects travel, mapmaking, ecosystems, and surface water flow and distribution. Over
9009-562: The early days of surveying, this was the primary method of determining accurate positions of objects for topographic maps of large areas. A surveyor first needs to know the horizontal distance between two of the objects, known as the baseline . Then the heights, distances and angular position of other objects can be derived, as long as they are visible from one of the original objects. High-accuracy transits or theodolites were used, and angle measurements were repeated for increased accuracy. See also Triangulation in three dimensions . Offsetting
9126-544: The first prototype satellites of the Global Positioning System (GPS) in 1978. GPS used a larger constellation of satellites and improved signal transmission, thus improving accuracy. Early GPS observations required several hours of observations by a static receiver to reach survey accuracy requirements. Later improvements to both satellites and receivers allowed for Real Time Kinematic (RTK) surveying. RTK surveys provide high-accuracy measurements by using
9243-467: The first triangulation of France. They included a re-surveying of the meridian arc , leading to the publication in 1745 of the first map of France constructed on rigorous principles. By this time triangulation methods were well established for local map-making. It was only towards the end of the 18th century that detailed triangulation network surveys mapped whole countries. In 1784, a team from General William Roy 's Ordnance Survey of Great Britain began
9360-490: The geological continents and the areas of shallow seabed close to their shores, known as continental shelves . This layer is sometimes called sial because its bulk composition is richer in aluminium silicate and has a lower density compared to the oceanic crust , called sima which is richer in magnesium silicate . Changes in seismic wave velocities have shown that at a certain depth (the Conrad discontinuity ), there
9477-748: The ground (about 20 km (12 mi) apart). This method reaches precisions between 5–40 cm (depending on flight height). Surveyors use ancillary equipment such as tripods and instrument stands; staves and beacons used for sighting purposes; PPE ; vegetation clearing equipment; digging implements for finding survey markers buried over time; hammers for placements of markers in various surfaces and structures; and portable radios for communication over long lines of sight. Land surveyors, construction professionals, geomatics engineers and civil engineers using total station , GPS , 3D scanners, and other collector data use land surveying software to increase efficiency, accuracy, and productivity. Land Surveying Software
9594-509: The ground to large beacons that can be seen from long distances. The surveyors can set up their instruments in this position and measure to nearby objects. Sometimes a tall, distinctive feature such as a steeple or radio aerial has its position calculated as a reference point that angles can be measured against. Triangulation is a method of horizontal location favoured in the days before EDM and GPS measurement. It can determine distances, elevations and directions between distant objects. Since
9711-409: The growth of coral reefs , and meteorite impacts are among the processes that constantly reshape Earth's surface over geological time . Erosion transports one part of land to another via natural processes, such as wind , water, ice , and gravity . In contrast, weathering wears away rock and other solid land without transporting the land somewhere else. Natural erosional processes usually take
9828-402: The harvest of crops. Floodplains provided agricultural land for some of the earliest civilizations . Erosion is often a main driver for the creation of plains and valleys, with rift valleys being a noticeable exception. Fjords are glacial valleys that can be thousands of meters deep, opening out to the sea. Any natural void in the ground which can be entered by a human can be considered
9945-400: The height difference is used to find the new elevation of the level gun, which is why this method is referred to as differential levelling . This is repeated until the series of measurements is completed. The level must be horizontal to get a valid measurement. Because of this, if the horizontal crosshair of the instrument is lower than the base of the rod, the surveyor will not be able to sight
10062-623: The igneous rocks granite and andesite . Less common is basalt , a denser volcanic rock that is the primary constituent of the ocean floors . Sedimentary rock is formed from the accumulation of sediment that becomes buried and compacted together . Nearly 75% of the continental surfaces are covered by sedimentary rocks, although they form about 5% of the crust. The most abundant silicate minerals on Earth's surface include quartz , feldspars , amphibole , mica , pyroxene and olivine . Common carbonate minerals include calcite (found in limestone ) and dolomite . The rock that makes up land
10179-476: The land is divided into two major categories: Mountain ranges and relatively flat interiors called cratons . Both form over millions of years through plate tectonics . Streams – a major part of Earth's water cycle – shape the landscape , carve rocks, transport sediments, and replenish groundwater. At high elevations or latitudes , snow is compacted and recrystallized over hundreds or thousands of years to form glaciers, which can be so heavy that they warp
10296-489: The land will influence how much solar radiation reaches its surface. High latitudes receive less solar radiation than low latitudes. The land's topography is important in creating and transforming airflow and precipitation . Large landforms, such as mountain ranges, can divert wind energy and make air parcels less dense and therefore able to hold less heat. As air rises, this cooling effect causes condensation and precipitation. Different types of land cover will influence
10413-425: The land's albedo , a measure of the solar radiation that is reflected, rather than absorbed and transferred to Earth. Vegetation has a relatively low albedo, meaning that vegetated surfaces are good absorbers of the sun's energy. Forests have an albedo of 10–15 percent while grasslands have an albedo of 15–20 percent. In comparison, sandy deserts have an albedo of 25–40 percent. Land use by humans also plays
10530-705: The land. Land cover refers to the material physically present on the land surface, for example, woody crops, herbaceous crops, barren land, and shrub-covered areas. Artificial surfaces (including cities) account for about a third of a percent of all land. Land use refers to human allocation of land for various purposes, including farming, ranching, and recreation (e.g. national parks); worldwide, there are an estimated 16.7 million km (6.4 million sq mi) of cropland, and 33.5 million km (12.9 million sq mi) of pastureland. Land cover change detection using remote sensing and geospatial data provides baseline information for assessing
10647-416: The law. They use equipment, such as total stations , robotic total stations, theodolites , GNSS receivers, retroreflectors , 3D scanners , lidar sensors, radios, inclinometer , handheld tablets, optical and digital levels , subsurface locators, drones, GIS , and surveying software. Surveying has been an element in the development of the human environment since the beginning of recorded history . It
10764-465: The low point of −418 m (−1,371 ft) at the Dead Sea , to a maximum altitude of 8,848 m (29,029 ft) at the top of Mount Everest. The mean height of land above sea level is about 797 m (2,615 ft), with 98.9% of dry land situated above sea level. Relief refers to the difference in elevation within a landscape; for example, flat terrain would have "low relief", while terrain with
10881-464: The measurement of angles. It uses two separate circles , protractors or alidades to measure angles in the horizontal and the vertical plane. A telescope mounted on trunnions is aligned vertically with the target object. The whole upper section rotates for horizontal alignment. The vertical circle measures the angle that the telescope makes against the vertical, known as the zenith angle. The horizontal circle uses an upper and lower plate. When beginning
10998-409: The measurement of vertical angles. Verniers allowed measurement to a fraction of a degree, such as with a turn-of-the-century transit . The plane table provided a graphical method of recording and measuring angles, which reduced the amount of mathematics required. In 1829 Francis Ronalds invented a reflecting instrument for recording angles graphically by modifying the octant . By observing
11115-424: The measuring instrument level would also be made. When measuring up a slope, the surveyor might have to "break" (break chain) the measurement- use an increment less than the total length of the chain. Perambulators , or measuring wheels, were used to measure longer distances but not to a high level of accuracy. Tacheometry is the science of measuring distances by measuring the angle between two ends of an object with
11232-411: The modern systematic use of triangulation . In 1615 he surveyed the distance from Alkmaar to Breda , approximately 72 miles (116 km). He underestimated this distance by 3.5%. The survey was a chain of quadrangles containing 33 triangles in all. Snell showed how planar formulae could be corrected to allow for the curvature of the Earth . He also showed how to resect , or calculate, the position of
11349-441: The ocean surface and leaves a ring of reefs around it. Mountains are features that usually rise at least 300 metres (980 ft) higher than the surrounding terrain. The formation of mountain belts is called orogenesis, and results from plate tectonics . For example, where a plate at a convergent plate boundary pushes one plate above the other, mountains could be formed by either collisional events, such that Earth's crust
11466-566: The orders of the court on conditional bail. The LTTE cadres including their leader V.Pirabhakaran had taken up residence at Mylapore Madras, while the leaders and members of the PLOTE had been staying at Saidapet, Madras. PLOTE lost its strength and momentum gradually due to continual conflicts with the LTTE. On July 16, 1989, Uma Maheswaran was assassinated in Colombo . A PLOTE splinter group claimed responsibility, though many still suspect Indian intelligence agency (RAW) involvement. Currently it
11583-672: The other Himalayan peaks. Surveying became a professional occupation in high demand at the turn of the 19th century with the onset of the Industrial Revolution . The profession developed more accurate instruments to aid its work. Industrial infrastructure projects used surveyors to lay out canals , roads and rail. In the US, the Land Ordinance of 1785 created the Public Land Survey System . It formed
11700-504: The outer part of the crust . Land plays an important role in Earth's climate system , being involved in the carbon cycle , nitrogen cycle , and water cycle . One-third of land is covered in trees, another third is used for agriculture , and one-tenth is covered in permanent snow and glaciers . The remainder consists of desert , savannah , and prairie . Land terrain varies greatly, consisting of mountains, deserts, plains, plateaus, glaciers, and other landforms . In physical geology,
11817-405: The past 150 years. Plate tectonics refers to the theory that Earth's lithosphere is divided into "tectonic plates" that move over the mantle. This results in continental drift , with continents moving relative to each other. The scientist Alfred Wegener first hypothesized the theory of continental drift in 1912. More researchers gradually developed his idea throughout the 20th century into
11934-408: The planet warms, it has been predicted that soils will add carbon dioxide to the atmosphere due to increased biological activity at higher temperatures, a positive feedback (amplification). This prediction has, however, been questioned on consideration of more recent knowledge on soil carbon turnover. Continental crust is the layer of igneous , sedimentary , and metamorphic rocks that forms
12051-433: The plant. Through photosynthesis , most plants nourish themselves from sunlight and water, breathing in carbon dioxide and breathing out oxygen. Between 20 and 50% of oxygen is produced by land vegetation. Unlike plants, terrestrial animals are not a monophyletic group —that is, a group including all terrestrial animals does not encompass all lineages from a common ancestor . This is because there are organisms, such as
12168-441: The primordial Earth had formed. Earth's atmosphere and oceans were formed by volcanic activity and outgassing that included water vapour . The origin of the world's oceans was condensation augmented by water and ice delivered by asteroids , protoplanets , and comets . In this model , atmospheric " greenhouse gases " kept the oceans from freezing while the newly formed Sun was only at 70% luminosity . By 3.5 bya ,
12285-428: The rod and get a reading. The rod can usually be raised up to 25 feet (7.6 m) high, allowing the level to be set much higher than the base of the rod. The primary way of determining one's position on the Earth's surface when no known positions are nearby is by astronomic observations. Observations to the Sun, Moon and stars could all be made using navigational techniques. Once the instrument's position and bearing to
12402-422: The satellite positions and atmospheric conditions. The surveyor uses the roving antenna to measure the points needed for the survey. The two antennas use a radio link that allows the static antenna to send corrections to the roving antenna. The roving antenna then applies those corrections to the GPS signals it is receiving to calculate its own position. RTK surveying covers smaller distances than static methods. This
12519-423: The surface of the Earth. Few survey positions are derived from the first principles. Instead, most surveys points are measured relative to previously measured points. This forms a reference or control network where each point can be used by a surveyor to determine their own position when beginning a new survey. Survey points are usually marked on the earth's surface by objects ranging from small nails driven into
12636-406: The survey, the surveyor points the instrument in a known direction (bearing), and clamps the lower plate in place. The instrument can then rotate to measure the bearing to other objects. If no bearing is known or direct angle measurement is wanted, the instrument can be set to zero during the initial sight. It will then read the angle between the initial object, the theodolite itself, and the item that
12753-536: The telescope aligns with. The gyrotheodolite is a form of theodolite that uses a gyroscope to orient itself in the absence of reference marks. It is used in underground applications. The total station is a development of the theodolite with an electronic distance measurement device (EDM). A total station can be used for leveling when set to the horizontal plane. Since their introduction, total stations have shifted from optical-mechanical to fully electronic devices. Modern top-of-the-line total stations no longer need
12870-459: The two endpoints. With the Global Positioning System (GPS), elevation can be measured with satellite receivers. Usually, GPS is somewhat less accurate than traditional precise leveling, but may be similar over long distances. When using an optical level, the endpoint may be out of the effective range of the instrument. There may be obstructions or large changes of elevation between the endpoints. In these situations, extra setups are needed. Turning
12987-446: The water on Earth. The vast majority of human activity throughout history has occurred in habitable land areas supporting agriculture and various natural resources . In recent decades, scientists and policymakers have emphasized the need to manage land and its biosphere more sustainably, through measures such as restoring degraded soil , preserving biodiversity , protecting endangered species , and addressing climate change . Land
13104-701: The widely accepted theory of plate tectonics of today. Several key characteristics define modern understanding of plate tectonics. The place where two tectonic plates meet is called a plate boundary , with different geological phenomena occurring across different kinds of boundaries. For example, at divergent plate boundaries , seafloor spreading is usually seen, in contrast with the subduction zones of convergent or transform plate boundaries . Earthquakes and volcanic activity are common in all types of boundaries. Volcanic activity refers to any rupture in Earth's surface where magma escapes, therefore becoming lava . The Ring of Fire , containing two-thirds of
13221-512: The widest, and mesas are a general-sized plateau with horizontal bedrock strata . Wide, flat areas of land are called plains , which cover more than one-third of Earth's land area. When they occur as lowered areas between mountains, they can create valleys , canyons or gorges, and ravines . A plateau can be thought of as an elevated plain. Plains are known to have fertile soils and be important for agriculture due to their flatness supporting grasses suitable for livestock and facilitating
13338-466: The world's volcanos, and over 70% of Earth's seismological activity , comprises plate boundaries surrounding the Pacific Ocean . Earth's land interacts with and influences its climate heavily, since the land's surface heats up and cools down faster than air or water. Latitude , elevation , topography , reflectivity , and land use all have varying effects on climate. The latitude of
13455-408: Was Athulathmudali, then Sri Lankan Prime Minister, who instigated PLOTE into such a venture on a promise of some islands. On May 19, 1982, a shootout occurred at about 9:45 p.m. at Pondy Bazaar , Mambalam , Madras between LTTE and PLOTE members. V. Prabhakaran and Raghavan (alias Sivakumar) of the LTTE, armed with revolvers , opened fire on Jotheeswaran and Mukundan (alias Uma Maheswaran) of
13572-506: Was arrested near Gummidipoondi railway station . At the time of arrest, he opened fire with his revolver and another case was registered against him under the Indian Arms Act . In the meantime, on May 23, 1982 Sivaneswaran (alias Niranjan), an accomplice of Mukundan, was also arrested at Saidapet, Madras and an unlicensed revolver seized from him. All these accused remained in custody until August 5, 1982 when they were released by
13689-504: Was the US Navy TRANSIT system . The first successful launch took place in 1960. The system's main purpose was to provide position information to Polaris missile submarines. Surveyors found they could use field receivers to determine the location of a point. Sparse satellite cover and large equipment made observations laborious and inaccurate. The main use was establishing benchmarks in remote locations. The US Air Force launched
#729270