THE EARTH. MERIDIANS AND PARALLELS

1=Circle of latitude
2=Meridian (geography)

A circle of latitude , on the Earth , is an imaginary east -west circle connecting all locations (not taking into account elevation) that share a given latitude . A location's position along a circle of latitude is given by its longitude .

Circles of latitude are often called parallels because they are parallel to each other. On some map projections, including the Equirectangular projection , they are drawn at equidistant intervals.

Circles of latitude become smaller the farther they are from the equator and the closer they are to the poles . A circle of latitude is perpendicular to all meridians at the points of intersection, and is hence a special case of a loxodrome .

Contrary to what might be assumed from their straight-line representation on some map projections, a circle of latitude is not, with the sole exception of the Equator, the shortest distance between two points lying on the Earth. In other words, circles of latitude (except for the Equator) are not great circles (see also great-circle distance ). It is for this reason that an airplane traveling between a European and North American city that share the same latitude will fly farther north, over Greenland for example.

Arcs of circles of latitude are sometimes used as boundaries between countries or regions where distinctive natural borders are lacking (such as in deserts), or when an artificial border is drawn as a "line on a map", as happened in Korea .

Longitude (λ)

Lines of longitude appear vertical with varying curvature in this projection; but are actually halves of great ellipses, with identical radii at a given latitude.

Latitude (φ)

Lines of latitude appear horizontal with varying curvature in this projection; but are actually circular with different radii. All locations with a given latitude are collectively referred to as a circle of latitude .

The equator divides the planet into aNorthern Hemisphere , a Southern Hemisphere and has a latitude of 0°.

Major circles of latitude

There are five major circles of latitude, listed below from north to south, with their values (Epoch 2010). [1] :

Arctic Circle (66° 33 ′ 44 ″ N)
Tropic of Cancer (23° 26 ′ 16 ″ N)
Equator (0° latitude)
Tropic of Capricorn (23° 26 ′ 16 ″ S)
Antarctic Circle (66° 33 ′ 44 ″ S)

These circles of latitude (excluding the equator) mark the divisions between the five principal geographical zones .

A meridian (or line of longitude ) is an imaginary arc on the Earth's surface from the North Pole to the South Pole that connects all locations running along it with a given longitude . The position of a point on the meridian is given by the latitude . Each meridian is perpendicular to all circles of latitude at the intersection points. Each is also the same size, being half of a great circle on the Earth's surface and therefore measuring 20,003.93 km.

Since the meridian that passes through Greenwich , England, establishes the meaning of zero degrees of longitude, or the Prime Meridian , any other meridian is identified by the angle, referenced to the center of the earth as vertex, between where it and the prime meridian cross the equator. As there are 360 degrees in a circle, the meridian on the opposite side of the earth from Greenwich (which forms the other half of a circle with the two through Greenwich) is 180° longitude , and the others lie between 0° and 180° of West lo ngitude in the Western Hemisphere (west of Greenwich) and between 0° and 180° of Eas t longitude in the Eastern Hemisphere (east of Greenwich). Most maps show the lines of longitude.

The term "meridian" comes from the Latin meridies , meaning "midday"; the sun crosses a given meridian midway between the times of sunrise and sunset on that meridian. The same Latin stem gives rise to the terms a.m. (ante meridiem) and p.m. (post meridiem) used to disambiguate hours of the day when using the 12-hour clock .

The magnetic meridian is an equivalent imaginary line connecting the magnetic south and north poles and can be taken as the magnetic force lines along the surface of the earth [1] . That is, a compass needle will be parallel to the magnetic meridian. The angle between the magnetic and the true meridian is the Magnetic declination , which is relevant for navigating with a compass. [2]

INGLÉS ESPAÑOL A meridian (or line of longitude ) Meridiano o línea de longitud A circle of latitude or paralel Círculo de latitud o paralelo zone huso Polar cap. Ice cap. Polar ice cap Casquete polar Zone (i.e. tropical zone) zona Time zones Husos horarios