Editing Vertical deflection (section)

==Components==
The deflection of the vertical has a [[meridian (astronomy)|north–south]] component ''ξ'' ([[Xi (letter)|xi]]) and an [[prime vertical|east–west]] component&nbsp;''η'' ([[Eta (letter)|eta]]). The value of ''ξ'' is the difference between the ''[[astronomic latitude]]'' and the ''[[geodetic latitude]]'' (taking north latitudes to be positive and south latitudes to be negative); the latter is usually calculated by geodetic network [[coordinate]]s. The value of ''η is'' the product of cosine of latitude and the difference between the ''[[astronomic longitude]]'' and the [[longitude]] (taking east longitudes to be positive and west longitudes to be negative). When a new [[mapping datum]] replaces the old, with new geodetic latitudes and longitudes on a new ellipsoid, the calculated vertical deflections will also change.