terminology
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Terminology
This terminology is generally sourced from Appendix A of 'Datums and Map Projections' (Iliffe & Lott 2008) based off the ISO 19111 terms.
| Term | Comment |
|---|---|
| Coordinate | A sequence of n numbers designating the position of a point in n-dimensional space |
| 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 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 (positive) or westwards (negative) from a north-south reference |
| 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 coordinate system | A coordinate system 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 |
terminology.1539065545.txt.gz · Last modified: 2018/10/09 17:12 by allchin09