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
Latitude ON a customizable, Linux-based Mobile Internet Device (MID) platform the laptop is able to boot almost instantly and view Email, document reader, calendar, contacts and access the Internet. First laptop models to include Latitude ON were E4200 and E4300 released in February 2009. Last laptop model introduced so far is Latitude Z600. Dell claims that battery life can be extended to days. Latitude ON Reader is similar to Dell's MediaDirect where the software is located in a separate partition on the system hard drive and has a dedicated button to power on. There are several versions of Latitude ON: Latitude ON