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terminology [2018/10/09 05:37]
allchin09
terminology [2018/10/09 06:29] (current)
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 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)| 
 +|Ellipsoidal height (//​h//​)|Distance of a point from the ellipsoid, measured along the perpendicular from the ellipsoid to the point| 
 +|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 longitude| Angle from the prime meridian plane to the meridian plane of a given point, positive eastwards| 
 +|Geoid| Equipotential surface of the Earth'​s gravity field, which is everywhere perpendicular to the direction of gravity and which best fits mean sea level| 
 +|Geoid-ellipsoid separation (//​N//​)|Height of the geoid above the ellipsoid| 
 +|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| 
 +|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.1539063440.txt.gz · Last modified: 2018/10/09 05:37 by allchin09