Summary: Georeferencing

Read the summary and the most important questions on Georeferencing

• 1 Reference surfaces for mapping

• 1.2 The Ellipsoid - horizontal datum

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• Why do we use geographic coordinates?

  To locate data on the Earth's reference surface (ellipsoid or sphere)

• How are locations identified in a geographic coordinate system?

  By latitude-longitude coordinates on a ellipsoid or sphere

• What is another word for geographic coordinate system?

  Geodetic datum system

• How are 3D geographic coordinates obtained?

  By introducing the ellipsodial height (h) to the system. Can be used to define a position on the surface of the earth

• Why are local datum systems established?

  To fit the Geoid well over an area of local interest

• When are Ellipsoids called geodetic datum systems?

  When they have a fixed position and orientation. In ArcGIS called: Geographic Coordinate Systems

• 2 Map projections

• 2.1 Classification of map projections

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• Explain the inverse mapping equation

  It transforms the Cartesian map coordinates of a point on the map plane to a set of geographic coordinates on the curved reference surface. Iput are the map coordinates of a point, output are the geographic coordinates of the point

• Explain the scale distortions on Mercator projection

  Angles and shapes (of small areas) are show correctly on the map. The shapes of the continents are reasonably well preserved. Shapes of areas are not correctly represented

• Explain a conformal distortion property

  When it represents angles and shapes (of small areas) corretly

• Explain a equidistant distortion property

  When it represents the certain directions correctly