Latitude & Longitude | Geography (Prelims) by Valor Academy - UPSC PDF Download

Latitude & Longitude

LATITUDE

It is the angular distance of a point on the earth’s surface, measured in degrees from the centre of the earth. Imaginary lines pointing the places of same latitude are called parallels of latitude since they are parallel to a line, the Equator, which lies midway between the globe, becoming matter poleward.

Some important parallels are:-

circle

LONGITUDE

It is the angular distance measured in degrees along the equator east or west of the Prime Meridian. On the globe the lines of longitude are drawn as a series of semicircles that extends from the North Pole to the South Pole through the Equator. They are also called Meridians. The Prime Meridian (0°) is that which passes through the Greenwich, near London and from which all other meridians radiate eastwards and westwards up to 180°.

AXIS:-An imaginary straight line joins the two poles on which the earth rotates.

POLES:-The two points on the earth through which the imaginary axis passes.

PARALLEL OF LATITUDES:-Imaginary circles running parallel to the equator.

MERIDIAN OF LONGITUDES:-Imaginary semicircles running from pole to pole.

LATITUDE:-It is a measure of angular distance of a given point from the equator. 1° (degree) = 60’ (60 minutes) = 3600” (seconds).

The distance from the equator to either of the poles is 1/4^th of a circle round the earth; it will measure 1/4^th of 360°, i.e. 90°.

IMPORTANT LONGITUDES AND LATITUDES AND HEAT ZONES

TORRID ZONE :- The area, between the Tropic of Cancer and Capricorn which receives the maximum heat as the midday sun is exactly overhead at least once a year.

TEMPARATE ZONE:-The area bounded by the Tropic of cancer and the Arctic circle in the Northern Hemisphere, and the Tropic of Capricorn and the Antartic circles in the Southern Hemisphere which has moderate temperature.

FRIGID ZONE: - The very cold area lying between the Arctic circle and the North Pole in the Northern Hemisphere and the Antarctic Circle and the South Pole in the Southern Hemisphere as the sun does not rises much above the horizon.

CONCEPT OF TIME

Since the earth makes one complete revolution of 360° in one day of 24 hours, it passes through 15° in one hour or 1° in 4 minutes. The earth rotates from west to east, so every 15° we go eastward, local time is advanced by one hour. Conversely, if we go westwards, local time is retarted by one hour. We may then conclude that places east of Greenwich see the sun earlier and gain time, whereas places west of Greenwich see the sun later and lose time. If we know G.M.T, to know local time, we merely have to add or subtract the difference in the number of hours from the given longitude.

STANDARD TIME

If each town were to keep the time of its own meridian, there would be much difference in local time between one town and the other. To avoid such difficulty, a system of Standard Time is observed by all countries. Most countries adopt their standard time from the central meridian of their countries. The Indian Government has accepted the meridian of 82.5° east for the standard time which is 5 hours and 30 minutes ahead of G.MT.

The whole world has in fact been divided into 24 Standard Time Zones, each of which differs from the next by 15° in longitude or one hour in time.

INTERNATIONAL DATE LINE

An imaginary line on the globe, approximately along the 180° meridian of longitude. When a person crosses this line from East to West, he gains one day and when he crosses from West to East, he loses one day.