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Geographic Coordinate System A GEOGRAPHIC COORDINATE SYSTEM is a coordinate system used in geography that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are often chosen such that one of the numbers represents a vertical position , and two or three of the numbers represent a horizontal position . A common choice of coordinates is latitude , longitude and elevation . To specify a location on a twodimensional map requires a map projection [...More...]  "Geographic Coordinate System" on: Wikipedia Yahoo 

Coordinate System In geometry , a COORDINATE SYSTEM is a system which uses one or more numbers , or COORDINATES, to uniquely determine the position of a point or other geometric element on a manifold such as Euclidean space . The order of the coordinates is significant, and they are sometimes identified by their position in an ordered tuple and sometimes by a letter, as in "the _x_coordinate". The coordinates are taken to be real numbers in elementary mathematics , but may be complex numbers or elements of a more abstract system such as a commutative ring . The use of a coordinate system allows problems in geometry to be translated into problems about numbers and _vice versa_; this is the basis of analytic geometry [...More...]  "Coordinate System" on: Wikipedia Yahoo 

Geography GEOGRAPHY (from Greek γεωγραφία, _geographia_, literally "earth description" ) is a field of science devoted to the study of the lands, the features, the inhabitants, and the phenomena of Earth Earth . The first person to use the word "γεωγραφία" was Eratosthenes (276–194 BC). Geography Geography is an allencompassing discipline that seeks an understanding of the Earth Earth and its human and natural complexities—not merely where objects are, but how they have changed and come to be. Geography Geography is often defined in terms of the two branches of human geography and physical geography . Human geography deals with the study of people and their communities, cultures, economies and interactions with the environment by studying their relations with and across space and place [...More...]  "Geography" on: Wikipedia Yahoo 

Altitude ALTITUDE or HEIGHT (sometimes known as DEPTH) is defined based on the context in which it is used (aviation, geometry, geographical survey, sport, and many more). As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context. Although the term altitude is commonly used to mean the height above sea level of a location, in geography the term elevation is often preferred for this usage. Vertical distance measurements in the "down" direction are commonly referred to as depth [...More...]  "Altitude" on: Wikipedia Yahoo 

Nvector The NVECTOR representation is a threeparameter nonsingular representation wellsuited for replacing latitude and longitude as horizontal position representation in mathematical calculations and computer algorithms. Geometrically, the nvector for a given position on an ellipsoid is the outwardpointing unit vector that is normal in that position to the ellipsoid. For representing horizontal positions on Earth, the ellipsoid is a reference ellipsoid and the vector is decomposed in an Earthcentered Earthfixed coordinate system . It behaves smoothly at all Earth positions, and it holds the mathematical onetoone property. More in general, the concept can be applied to representing positions on the boundary of a strictly convex bounded subset of kdimensional Euclidean space Euclidean space , provided that that boundary is a differentiable manifold . In this general case, the nvector consists of k parameters [...More...]  "Nvector" on: Wikipedia Yahoo 

Horizontal Position Representation A POSITION REPRESENTATION is the parameters used to express a position relative to a reference. Representing position in three dimensions is often done by a Euclidean vector Euclidean vector . However, when representing position relative to the Earth Earth it is often more convenient to represent vertical position as altitude or depth, and to use some other parameters to represent HORIZONTAL POSITION. There are also several applications where only the horizontal position is of interest, this might e.g. be the case for ships and ground vehicles/cars. There are several options for horizontal position representations, each with different properties which makes them appropriate for different applications. Latitude Latitude /longitude and UTM are common horizontal position representations [...More...]  "Horizontal Position Representation" on: Wikipedia Yahoo 

Latitude In geography , LATITUDE is a geographic coordinate that specifies the north –south position of a point on the Earth's surface. Latitude Latitude is an angle (defined below) which ranges from 0° at the Equator Equator to 90° ( North North or South) at the poles. Lines of constant latitude, or _parallels_, run east–west as circles parallel to the equator. Latitude Latitude is used together with longitude to specify the precise location of features on the surface of the Earth. Without qualification the term latitude should be taken to be the _geodetic latitude_ as defined in the following sections. Also defined are six _auxiliary latitudes_ which are used in special applications [...More...]  "Latitude" on: Wikipedia Yahoo 

Longitude LONGITUDE (/ˈlɒndʒᵻtjuːd/ or /ˈlɒndʒᵻtuːd/ , Australian and British also /ˈlɒŋɡᵻtjuːd/ ), is a geographic coordinate that specifies the eastwest position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Meridians (lines running from the North Pole North Pole to the South Pole South Pole ) connect points with the same longitude. By convention, one of these, the Prime Meridian Prime Meridian , which passes through the Royal Observatory, Greenwich , England, was allocated the position of zero degrees longitude. The longitude of other places is measured as the angle east or west from the Prime Meridian, ranging from 0° at the Prime Meridian Prime Meridian to +180° eastward and −180° westward [...More...]  "Longitude" on: Wikipedia Yahoo 

Elevation The ELEVATION of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid , a mathematical model of the Earth\'s sea level as an equipotential gravitational surface (see Geodetic system, vertical datum ). Elevation, or GEOMETRIC HEIGHT, is mainly used when referring to points on the Earth's surface, while altitude or geopotential height is used for points above the surface, such as an aircraft in flight or a spacecraft in orbit, and depth is used for points below the surface. Elevation Elevation is not to be confused with the distance from the center of the Earth; due to equatorial bulge , the summits of Mt. Everest and Chimborazo have, respectively, the largest elevation and the largest geocentric distance [...More...]  "Elevation" on: Wikipedia Yahoo 

Map Projection A MAP PROJECTION is a systematic transformation of the latitudes and longitudes of locations from the surface of a sphere or an ellipsoid into locations on a plane . Maps cannot be created without map projections. All map projections necessarily distort the surface in some fashion. Depending on the purpose of the map, some distortions are acceptable and others are not; therefore, different map projections exist in order to preserve some properties of the spherelike body at the expense of other properties. There is no limit to the number of possible map projections. :1 More generally, the surfaces of planetary bodies can be mapped even if they are too irregular to be modeled well with a sphere or ellipsoid; see below . Even more generally, projections are a subject of several pure mathematical fields, including differential geometry , projective geometry , and manifolds . However, "map projection" refers specifically to a cartographic projection [...More...]  "Map Projection" on: Wikipedia Yahoo 

History Of Geodesy Geodesy Geodesy (/dʒiːˈɒdɨsi/), also named geodetics, is the scientific discipline that deals with the measurement and representation of the Earth. The HISTORY OF GEODESY began in antiquity and blossomed during the Age of Enlightenment . Early ideas about the figure of the Earth Earth held the Earth Earth to be flat (see flat Earth Earth ), and the heavens a physical dome spanning over it. Two early arguments for a spherical Earth Earth were that lunar eclipses were seen as circular shadows which could only be caused by a spherical Earth, and that Polaris Polaris is seen lower in the sky as one travels South [...More...]  "History Of Geodesy" on: Wikipedia Yahoo 

History Of Longitude The HISTORY OF LONGITUDE is a record of the effort, by astronomers, cartographers and navigators over several centuries, to discover a means of determining longitude . The measurement of longitude is important to both cartography and navigation , in particular to provide safe ocean navigation. Knowledge of both latitude and longitude was required. Finding an accurate and reliable method of determining longitude took centuries of study, and involved some of the greatest scientific minds in human history [...More...]  "History Of Longitude" on: Wikipedia Yahoo 

History Of Prime Meridians A PRIME MERIDIAN is a meridian (a line of longitude ) in a geographical coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its antimeridian (the 180th meridian in a 360°system ) form a great circle . This great circle divides the sphere, e.g., the Earth Earth , into two hemispheres . If one uses directions of East and West from a defined prime meridian, then they can be called Eastern Hemisphere Eastern Hemisphere and Western Hemisphere Western Hemisphere . Gerardus Mercator Gerardus Mercator in his Atlas Cosmographicae Atlas Cosmographicae (1595) uses a prime meridian somewhere close to 25°W , passing just to the west of Santa Maria Island in the Atlantic Atlantic [...More...]  "History Of Prime Meridians" on: Wikipedia Yahoo 

Invention An INVENTION is a unique or novel device , method, composition or process. The invention process is a process within an overall engineering and product development process. It may be an improvement upon a machine or product or a new process for creating an object or a result. An invention that achieves a completely unique function or result may be a radical breakthrough. Such works are novel and not obvious to others skilled in the same field . An inventor may be taking a big step in success or failure. Some inventions can be patented. A patent legally protects the intellectual property rights of the inventor and legally recognizes that a claimed invention is actually an invention. The rules and requirements for patenting an invention vary from country to country and the process of obtaining a patent is often expensive. Another meaning of invention is CULTURAL INVENTION , which is an innovative set of useful social behaviours adopted by people and passed on to others [...More...]  "Invention" on: Wikipedia Yahoo 

Eratosthenes ERATOSTHENES OF CYRENE (/ɛrəˈtɒsθəniːz/ ; Greek : Ἐρατοσθένης ὁ Κυρηναῖος, IPA: ; c. 276 BC – c. 195/194 BC ) was a Greek mathematician , geographer , poet , astronomer , and music theorist . He was a man of learning, becoming the chief librarian at the Library of Alexandria Alexandria . He invented the discipline of geography , including the terminology used today. He is best known for being the first person to calculate the circumference of the Earth , which he did by applying a measuring system using stadia , a standard unit of measure during that time period. His calculation was remarkably accurate. He was also the first to calculate the tilt of the Earth\'s axis (again with remarkable accuracy). Additionally, he may have accurately calculated the distance from the Earth to the Sun Sun and invented the leap day [...More...]  "Eratosthenes" on: Wikipedia Yahoo 

Cyrene, Libya CYRENE (/saɪˈriːniː/ ; Ancient Greek : Κυρήνη, translit. Kyrēnē) was an ancient Greek and Roman city near presentday Shahhat , Libya Libya . It was the oldest and most important of the five Greek cities in the region. It gave eastern Libya Libya the classical name Cyrenaica Cyrenaica that it has retained to modern times. Nearby located, the ancient Necropolis of Cyrene Necropolis of Cyrene . Cyrene lies in a lush valley in the Jebel Akhdar uplands. The city was named after a spring , Kyre, which the Greeks Greeks consecrated to Apollo Apollo . It was also the seat of the Cyrenaics Cyrenaics , a famous school of philosophy in the 4th century BC, founded by Aristippus Aristippus , a disciple of Socrates Socrates . It was then nicknamed the " Athens Athens of Africa" [...More...]  "Cyrene, Libya" on: Wikipedia Yahoo 