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terminology

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terminology [2018/10/09 05:23] allchin09 created |
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====== Terminology ====== | ====== Terminology ====== | ||

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+ | This terminology is generally sourced from Appendix A of 'Datums and Map Projections' (Iliffe & Lott 2008) based off the ISO 19111 terms. | ||

^ Term ^ Comment ^ | ^ Term ^ Comment ^ | ||

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| Coordinate conversion |Change of coordinates from one CRS to another in which the two CRSs are based on the same datum| | | Coordinate conversion |Change of coordinates from one CRS to another in which the two CRSs are based on the same datum| | ||

| Coordinate operation |Change of coordinates with a 1-to-1 relationship, from one CRS to another. Comprised of coordinate conversion and coordinate transformation processes| | | Coordinate operation |Change of coordinates with a 1-to-1 relationship, from one CRS to another. Comprised of coordinate conversion and coordinate transformation processes| | ||

- | | | + | | Coordinate reference system (CRS) | A coordinate system that through a datum, has defined position, scale and orientation with respect to an object (usually the Earth)| |

+ | |Coordinate system| Set of rules defining how coordinates are assigned to points| | ||

+ | |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| | ||

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