THE EARTH. MERIDIANS AND PARALLELS

Size: px

Start display at page:

Download "THE EARTH. MERIDIANS AND PARALLELS"

Basil Quinn
6 years ago
Views:

1 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

2 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

3 There are five major circles of latitude, listed below from north to south, with their values (Epoch 2010). [1] : Arctic Circle ( N) Tropic of Cancer ( N) Equator (0 latitude) Tropic of Capricorn ( S) Antarctic Circle ( 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 latitudeat the intersection points. Each is also the same size, being half of a great circle on the Earth's surface and therefore measuring 20, 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]

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

5 EXERCISES (word problems) 1. Two cities are located on two meridians. The angle between these meridians is 225. What will be the time difference? 2. Find the surface area of the Earth knowing that its radius is 6371 km. 3. Find the distance between two points on Earth, knowing that the geographic coordinates are A(10 W, 25 S) and B(10 W,55 S). R=6371 Km. 4. The geographical coordinates of a town are (15 E, 45 N). Find the distance of this town to the equator measured over the town s meridian. 5. In geography, the antipodes of any place on Earth is the point on the Earth's surface which is diametrically opposite to it. Two points that are antipodal to each other are connected by a straight line running through the centre of the Earth. Find the geographical coordinates of the antipodes of Rome (12 40 E, N). 6. What are the geographical coordinates of the north and south poles? 7. Find the surface area of a time zone (un huso horario). R = 6371 km. 8. Calculate the distance traveled by an airplane flying along the common parallel from a point in Europe with geographical coordinates of (8 E, 45 N) to another point in America with coordinates (70 W, 45 N). 9. Two points A and B are located on the equator with longitudes of 20 E and 20 W. What is the distance between them?. Length of equator=40030 km.

Module 2: Mapping Topic 2 Content: Determining Latitude and Longitude Notes

Module 2: Mapping Topic 2 Content: Determining Latitude and Longitude Notes Introduction In order to more easily locate points on a globe or map, cartographers designed a system of imaginary vertical lines (also called parallels) and horizontal lines (also called meridians) that