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terminology

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terminology [2018/10/09 06:12] allchin09 |
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|Coordinate transformation| Change of coordinates from one CRS to another, where the CRSs datums differ| | |Coordinate transformation| Change of coordinates from one CRS to another, where the CRSs datums differ| | ||

|Datum| Defines the position of the origin, the scale and the orientation of the axis of a coordinate system with respect to an object| | |Datum| Defines the position of the origin, the scale and the orientation of the axis of a coordinate system with respect to an object| | ||

- | |Easting| Distance in a CRS eastwards (positive) or westwards (negative) from a north-south reference| | + | |Easting| Distance in a CRS eastwards from a north-south reference line, positive eastwards| |

|Ellipsoid| A closed surface formed by the rotation of an ellipse about a main axis. The figure of the Earth is usually modelled as an ellipsoid which is slightly squished from the shape of a sphere at the poles. Shape usually described by terms //a// and //b// (semi-major and semi-minor axis lengths) or //a// and //f-inverse// (inverse flattening)| | |Ellipsoid| A closed surface formed by the rotation of an ellipse about a main axis. The figure of the Earth is usually modelled as an ellipsoid which is slightly squished from the shape of a sphere at the poles. Shape usually described by terms //a// and //b// (semi-major and semi-minor axis lengths) or //a// and //f-inverse// (inverse flattening)| | ||

|Ellipsoidal height (//h//)|Distance of a point from the ellipsoid, measured along the perpendicular from the ellipsoid to the point| | |Ellipsoidal height (//h//)|Distance of a point from the ellipsoid, measured along the perpendicular from the ellipsoid to the point| | ||

- | |Geodetic coordinate system|A coordinate system where position is specified by geodetic latitude, geodetic longitude and (for 3d case) ellipsoidal height| | + | |Geodetic CRS|A CRS where position is specified by geodetic latitude, geodetic longitude and (for 3d case) ellipsoidal height| |

|Geodetic latitude| Angle from the equatorial plane to the perpendicular to the ellipsoid through a given point, positive northwards| | |Geodetic latitude| Angle from the equatorial plane to the perpendicular to the ellipsoid through a given point, positive northwards| | ||

|Geodetic longitude| Angle from the prime meridian plane to the meridian plane of a given point, positive eastwards| | |Geodetic longitude| Angle from the prime meridian plane to the meridian plane of a given point, positive eastwards| | ||

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|Gravity-related height (//H//)|Height dependent on the Earth's gravity field, such as orthometric or normal height, which both are approximations of the distance of a point above mean sea level. //H// = //h// + //N//| | |Gravity-related height (//H//)|Height dependent on the Earth's gravity field, such as orthometric or normal height, which both are approximations of the distance of a point above mean sea level. //H// = //h// + //N//| | ||

|Height| Either ellipsoidal or gravity-related height| | |Height| Either ellipsoidal or gravity-related height| | ||

- | + | |Map projection| Coordinate conversion from an ellipsoidal coordinate system to a plane| | |

- | + | |Mean sea level (//MSL//)| Averal level of the surface of the sea over all stages of tide and seasonal variations. Usually defined for a local region from observations of one or more points over a period of time| | |

+ | |Meridian| Intersection of an ellipsoid by a plane containing the shortest axis of the ellipsoid| | ||

+ | |Northing| Distance in a CRS from an east-west reference line, positive northwards| | ||

+ | |Prime meridian| Meridian from which the longitudes of other meridians are quantified| | ||

+ | |Projected CRS| A CRS derived from a 2D geodetic CRS by applying a map projection| | ||

+ | |Vertical CRS| A 1D CRS based on a vertical datum| | ||

+ | |Vertical datum| A datum describing the relation of gravity-related heights or depths to the Earth, usually related to //MSL//. Ellipsoidal heights are instead treated as being related to a 3D ellipsoidal CRS| |

terminology.txt · Last modified: 2018/10/09 06:29 by allchin09