Latitude and Longitude
Any location on Earth is described by two
numbers -its latilude and its longitude
Latitude
On a globe of the Earth, lines of latitude are
circles of different size. The longest is the equaton
whose latitude is zero, while at the poles at
latitudes 90 north and 90 south (or -909) the
circles shrink to a point
Longitude
On the globe, lines of constant longitude
(meridians') extend from pole to pole
Every meridian must cross the equator Since the equator is a circle, we can
divide it-like any circle-into 360 degrees, and the longitude of a point is then the
marked value of that division where its meridian meets the equator
For historical reasons, the longitude (meridian) passing the old Royal
Astronomical Observatory in Greenwich, England, is the one chosen as zero
longitude. Located at the eastern edgeof London, the British capital, the observatory
is now a public museum and a brass bandstretching across its yard marks the 'prime
meridian
A line of longitude is also called a meridian, derived from the Latin, from
meri, a variation of 'medius which denotes middle, and diem, meaning day
The word once meant "noon, and times of the day before noon were known as
ante meridian, while times after it were 'post meridian, Today's abbreviations
am.and pm come from these terms and the Sun at noon was said to be pasing
meridian" All points on the same line of longitude experienced noon (and any
other hour) at the same time and were therefore sald to be on the same "meridián
Local Time (LT) and Time Zones
Two important concepts,related to latitude and (especially)longitude are LocalTime (LI) and Universal Time (UT)
·Longitudes are measured from zero to 180" east and 180° west (or-180°), and
both 180- degree longitudes share the same line, in the middle of the Pacific Ocean
As the Earth rotates around its axis, at any moment one line of longitude "the
n meridian" faces the Sun, and at that moment, it will be noon everywhere on it.
After 24 hours the Earth has undergone a full rotation with respect to the Sun, and
Tc same meridian again faces noon. Thus each hour the Earth rotaten by 360/24-
The Date Line and Universal Time (UD
