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Azimuth An azimuth (/ˈæzɪməθ/ ( listen)) (from the pl. form of the Arabic noun "السَّمْت" assamt, meaning "the direction") is an angular measurement in a spherical coordinate system. The vector from an observer (origin) to a point of interest is projected perpendicularly onto a reference plane; the angle between the projected vector and a reference vector on the reference plane is called the azimuth. An example of azimuth is the angular direction of a star in the sky. The star is the point of interest, the reference plane is the local horizontal area (e.g. a circular area 5 km in radius around an observer at sea level), and the reference vector points north. The azimuth is the angle between the north vector and the star's vector on the horizontal plane.[1] Azimuth Azimuth is usually measured in degrees (°) [...More...]  "Azimuth" on: Wikipedia Yahoo 

Angular Mil A milliradian, often called a mil or mrad, is an SI derived unit SI derived unit for angular measurement which is defined as a thousandth of a radian (0.001 radian). Mils are used in adjustment of firearm sights by adjusting the angle of the sight compared to the barrel (up, down, left or right). Mils are also used for comparing shot groupings, or to compare the difficulty of hitting different sized shooting targets at different distances. When using a scope with both mil adjustment and a reticle with mil markings (called a mil/mil scope), the shooter can use the reticle as a "ruler" to count the number of mils a shot was off target which directly translates to the sight adjustment needed to hit the target with a follow up shot [...More...]  "Angular Mil" on: Wikipedia Yahoo 

Hour Angle In astronomy and celestial navigation, the hour angle is one of the coordinates used in the equatorial coordinate system to give the direction of a point on the celestial sphere. The hour angle of a point is the angle between two planes: one containing the Earth's axis and the zenith (the meridian plane), and the other containing the Earth's axis and the given point (the hour circle passing through the point).As seen from above the Earth's north pole, a star's local hour angle (LHA) for an observer near New York (red dot). Also depicted are the star's right ascension and Greenwich hour angle (GHA), the local mean sidereal time (LMST) and Greenwich mean sidereal time (GMST). The symbol ʏ identifies the vernal equinox direction.The angle may be expressed as negative east of the meridian plane and positive west of the meridian plane, or as positive westward from 0° to 360° [...More...]  "Hour Angle" on: Wikipedia Yahoo 

Alpha Alpha Alpha (uppercase Α, lowercase α; Ancient Greek: ἄλφα, álpha, modern pronunciation álfa) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of 1. It was derived from the Phoenician and Hebrew Hebrew letter aleph  an ox or leader.[1] Letters that arose from alpha include the Latin Latin A and the Cyrillic letter А. In English, the noun "alpha" is used as a synonym for "beginning", or "first" (in a series), reflecting its Greek roots.[2]Contents1 Uses1.1 Greek1.1.1 Greek grammar1.2 Math and science 1.3 International Phonetic Alphabet2 History and symbolism2.1 Etymology 2.2 Plutarch 2.3 Alpha Alpha and Omega 2.4 Language3 Computer encodings 4 ReferencesUses Greek In Ancient Greek, alpha was pronounced [a] and could be either phonemically long ([a:]) or short ([a]) [...More...]  "Alpha" on: Wikipedia Yahoo 

Clockwise And Counterclockwise Twodimensional rotation can occur in two possible directions. A clockwise (typically abbreviated as CW) motion is one that proceeds in the same direction as a clock's hands: from the top to the right, then down and then to the left, and back up to the top [...More...]  "Clockwise And Counterclockwise" on: Wikipedia Yahoo 

Meridian (geography) A (geographical) meridian (or line of longitude) is the half of an imaginary great circle on the Earth's surface, terminated by the North Pole and the South Pole, connecting points of equal longitude. The position of a point along the meridian is given by its latitude indicating how many degrees north or south of the Equator Equator the point is. Each meridian is perpendicular to all circles of latitude. Each is also the same length, being half of a great circle on the Earth's surface and therefore measuring 20,003.93 km (12,429.9 miles).Contents1 Etymology 2 Geographic 3 Magnetic 4 See also 5 References 6 External linksEtymology[edit] The term "meridian" comes from the Latin meridies, meaning "midday"; the sun crosses a given meridian midway between the times of sunrise and sunset on that meridian. The same Latin stem gives rise to the terms a.m. (ante meridiem) and p.m [...More...]  "Meridian (geography)" on: Wikipedia Yahoo 

True North True north (also called geodetic north) is the direction along Earth's surface towards the geographic North Pole. Geodetic north differs from magnetic north (the direction a compass points toward the Magnetic North Pole), and from grid north (the direction northwards along the grid lines of a map projection). Geodetic true north also differs very slightly from astronomical true north (typically by a few arcseconds) because the local gravity may not point at the exact rotational axis of Earth. The direction of astronomical true north is marked in the skies by the north celestial pole. This is within about 1° of the position of Polaris, so that the star would appear to trace a tiny circle in the sky each sidereal day. Due to the axial precession of Earth, true north rotates in an arc with respect to the stars that takes approximately 25,000 years to complete [...More...]  "True North" on: Wikipedia Yahoo 

Grad (angle) The gradian is a unit of measurement of an angle, equivalent to 1 400 textstyle frac 1 400 of a turn,[1] 9 10 textstyle frac 9 10 of a degree, or π 200 textstyle frac pi 200 of a radian. It is also known as gon (from Greek γωνία/gōnía for angle), grad, or grade. In continental Europe, the French term centigrade was in use for one hundredth of a grad. This was one reason for the adoption of the term Celsius Celsius to replace centigrade as the name of the temperature scale.[2][3]Contents1 History 2 Benefits 3 Use in surveying 4 Conversion 5 See also 6 References 7 External linksHistory[edit] The unit originated in connection with the French Revolution French Revolution in France as the grade, along with the metric system, hence it is occasionally referred to as a "metric degree" [...More...]  "Grad (angle)" on: Wikipedia Yahoo 

Sightline A sightline (also sight line) or visual axis is a normally unobstructed line of sight between an intended observer (or spectator) and a subject of interest, such as a stage, arena, or monument. Sightlines are a particularly important consideration in theatre and stadium design, road junction layout and urban planning. In cities such as London, construction within sightlines is restricted to protect the key views of famous landmarks.[1] Subjects that have a direct line of sight with one another are said to be intervisible.Contents1 Cvalue 2 Sightlines in theatres 3 Sightlines in stadiums3.1 Sightlines in plan 3.2 Focus point4 Obstructed view seats 5 FIFA CValue standards 6 Research 7 ReferencesCvalue[edit] Good sightlines allow spectators to see all areas of a venue stage or field of play [...More...]  "Sightline" on: Wikipedia Yahoo 

Spatial Reference System A spatial reference system (SRS) or coordinate reference system (CRS) is a coordinatebased local, regional or global system used to locate geographical entities. A spatial reference system defines a specific map projection, as well as transformations between different spatial reference systems. Spatial reference systems are defined by the OGC's Simple feature access using wellknown text, and support has been implemented by several standardsbased geographic information systems. Spatial reference systems can be referred to using a SRID SRID integer, including EPSG EPSG codes defined by the International Association of Oil and Gas Producers [...More...]  "Spatial Reference System" on: Wikipedia Yahoo 

Culmination In astronomy, the culmination of a planet, star, or constellation is its transit over an observer's meridian.[1][2] During a sidereal day, an astronomical object crosses the meridian twice: once at its upper culmination, when it is approximately at its highest point as seen from the Earth, and once at its lower culmination, its approximately lowest point. Often, culmination is used to mean upper culmination.[1][2][3] The altitude of an object in degrees at its upper culmination is equal to (90 − L + D), where L is the observer's latitude and D is the object's declination.Contents1 Cases 2 Period 3 Sun 4 Polaris 5 See also 6 ReferencesCases[edit] The three cases are dependent on the observer's latitude and the declination of the celestial body:The object is above the horizon even at its lower culmination; i.e. if declination + latitude > 90° (i.e [...More...]  "Culmination" on: Wikipedia Yahoo 

Astronomy Astronomy Astronomy (from Greek: ἀστρονομία) is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, galaxies, and comets; the phenomena include supernova explosions, gamma ray bursts, and cosmic microwave background radiation. More generally, all phenomena that originate outside Earth's atmosphere Earth's atmosphere are within the purview of astronomy. A related but distinct subject, physical cosmology, is concerned with the study of the Universe Universe as a whole.[1] Astronomy Astronomy is one of the oldest of the natural sciences [...More...]  "Astronomy" on: Wikipedia Yahoo 

Radian The radian (SI symbol rad) is the SI unit for measuring angles, and is the standard unit of angular measure used in many areas of mathematics. The length of an arc of a unit circle is numerically equal to the measurement in radians of the angle that it subtends; one radian is just under 57.3 degrees (expansion at A072097). The unit was formerly an SI supplementary unit, but this category was abolished in 1995 and the radian is now considered an SI derived unit.[1] Separately, the SI unit of solid angle measurement is the steradian. The radian is most commonly represented by the symbol rad.[2] An alternative symbol is c, the superscript letter c (for "circular measure"), the letter r, or a superscript R,[3] but these symbols are infrequently used as it can be easily mistaken for a degree symbol (°) or a radius (r) [...More...]  "Radian" on: Wikipedia Yahoo 

Atan2 In a variety of computer languages, the functionality of the multivalued inverse tangent is provided under the function names of atan2 ( y , x ) displaystyle operatorname atan2 (y,x) or arctan2 ( y , x ) displaystyle operatorname arctan2 (y,x) . This function takes two arguments y and x, not both equal to zero, representing the coordinates of an arbitrary point ( x , y ) displaystyle (x,y) in the X/Yplane, excluding the origin. The ratio y / x displaystyle y/x is interpreted as the tangent of an angle θ , displaystyle theta , spanned by the Xaxis and the ray from the origin to this point [...More...]  "Atan2" on: Wikipedia Yahoo 

World Geodetic System The World Geodetic System World Geodetic System (WGS) is a standard for use in cartography, geodesy, and navigation including GPS [...More...]  "World Geodetic System" on: Wikipedia Yahoo 

Cape Town Cape Town Cape Town (Afrikaans: Kaapstad, [ˈkɑːpstat]; Xhosa: iKapa) is a coastal city in South Africa. It is the secondmost populous urban area in South Africa South Africa after Johannesburg.[6] It is also the capital and primate city of the Western Cape Western Cape province.[7] As the seat of the Parliament of South Africa, it is also the legislative capital of the country.[8] It forms part of the City City of Cape Town Cape Town metropolitan municipality. The city is famous for its harbour, for its natural setting in the Cape Floristic Region, and for such wellknown landmarks as Table Mountain Table Mountain and Cape Point [...More...]  "Cape Town" on: Wikipedia Yahoo 