Latitude constant latitude and constant longitude, which are constructed with reference to the rotation axis of the Earth. The primary reference points are the poles where the axis of rotation of the Earth intersects the reference surface. Planes which contain the rotation axis intersect the surface at the meridians; and the angle between any one meridian plane and that through Greenwich (the Prime Meridian) defines the longitude: meridians are lines of constant longitude. The plane through the centre of the Earth and perpendicular to the rotation axis intersects the surface at a great circle called the Equator. Planes parallel to the
Dell Latitude Latitude line generally retains identical components throughout its production. This design is intended to simplify maintenance and support tasks for large corporations, allowing components to be easily swapped between models. The lines of Dell Latitude personal computers are currently in the "E" series, which is the successor to the popular Latitude D, C, and X series. The Latitudes from the early 1990s up until the C*00 lines weren't in a set "series", instead going under the models CP and XP with modifiers at the end, e.g.: XPi, CP M233. In the past, the "mainstream" line was the 6 series, being