ArcGIS terminology Define projection Specify the projection for some data

Arcgis terminology define projection specify the

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ArcGIS terminologyDefine projection.Specify the projection for some data without changing the data.Project.Change the data from one projection to another. dr gemson, IIAEM, JU, Bangalore49* ArcGISis a geographic information system (GIS) for working with maps and geographicinformation. It is used for creating and using maps, compiling geographic data, analyzing mappedinformation,sharinganddiscoveringgeographicinformation,usingmapsandgeographicinformation in a range of applications, and managing geographic information in a database.
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Types of Coordinate Systems(1) Global Cartesian coordinates (x, y, z) for the whole earth(2) Geographic coordinates (, , z) (3) Projected coordinates (x, y, z) on a local area of the earth’s surfaceThe z-coordinate in (1) and (3) are defined geometrically; in (2) the z-coordinate is defined gravitationallydr gemson, IIAEM, JU, Bangalore50
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Global Cartesian Coordinates (x,y,z)OXZYGreenwichMeridianEquatordr gemson, IIAEM, JU, Bangalore51
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Geographic Coordinates (, , z)Latitude () and Longitude () defined using an ellipsoid, an ellipse rotated about an axisElevation (z) defined using geoid, a surface of constant gravitational potentialEarth datums define standard values of the ellipsoid and geoiddr gemson, IIAEM, JU, Bangalore52
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Shape of the EarthWe think of the earth as a sphereIt is actually a spheroid, slightly larger in radius at the equator than at the polesdr gemson, IIAEM, JU, Bangalore53
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EllipsePF2OF1abXZAn ellipse is defined by:Focal length = Distance (F1, P, F2) isconstant for all pointson ellipseWhen = 0, ellipse = circleFor the earth:Major axis, a = 6378 kmMinor axis, b = 6357 kmFlattening ratio, f = (a-b)/a ~ 1/300dr gemson, IIAEM, JU, Bangalore54
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Ellipsoid or SpheroidRotate an ellipse around an axisOXZYaabRotational axisdr gemson, IIAEM, JU, Bangalore55
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Standard Ellipsoids of EarthEllipsoidMajoraxis, a (m)Minoraxis, b (m)Flatteningratio, fClarke(1866)6,378,2066,356,5841/294.98GRS806,378,1376,356,7521/298.57Ref: Snyder, Map Projections, A working manual, USGSProfessional Paper 1395, p.12dr gemson, IIAEM, JU, Bangalore56
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Horizontal Earth DatumsAn earth datum is defined by an ellipse and an axis of rotationNAD27 (North American Datum of 1927) uses the Clarke (1866) ellipsoid on a non geocentric axis of rotationNAD83 (NAD,1983) uses the GRS80 ellipsoid on a geocentric axis of rotationWGS84 (World Geodetic System of 1984) uses GRS80, almost the same as NAD83dr gemson, IIAEM, JU, Bangalore57
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Definition of Latitude, (1) Take a point S on the surface of the ellipsoid and define there the tangent plane, mn(2) Define the line pq through S and normal to the tangent plane(3) Angle pqr which this line makes with the equatorial plane is the latitude , of point SOSmnqprdr gemson, IIAEM, JU, Bangalore58
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Cutting Plane of a MeridianPMeridianEquatorplanePrime Meridiandr gemson, IIAEM, JU, Bangalore59
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Definition of Longitude, 0°E, W90°W(-90 °)180°E, W90°E(+90 °)-120°-30°-60°-150°30°-60°120°150°= the angle between a cutting plane on the prime meridianand the cutting plane on the meridian through the point, PPdr gemson, IIAEM, JU, Bangalore60
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