6.Chapter3.Geo.Locating Places on the Earth

Chapter 3.Geography.

Locating Places on the Earth

Page 21 We know that distance and direction help us to locate a place on a map or a globe.  If we are at a new place, we try to observe certain features of our surroundings.  These features, such as a temple, a hill or a river help us in locating places.  These features are called the reference points or landmarks The earth being spherical in shape has no edges or corners which can be used as reference points in locating the places.  However, the end points of the imaginary axis of the earth on which it rotates, provide us two basic points of reference.  These end points of the earth's axis are called North Pole and South Pole.  These are the fixed points on the earth.  The South Latitude North Pole lies exactly below the Pole Star and opposite to it is the South Pole.  Using the two Poles as basic reference points, an imaginary circle is drawn around the earth midway between the two Poles.  This great circle, divides the earth into two halves, and is known as the Equator.  The half portion of the earth to the north of the Equator is called the Northern Hemisphere.  The southern half is called the Southern Hemisphere.  A perpendicular line from any of the Poles to the Equator makes an angle of 90 °.  Thus, the North Pole is at 90 'N and the South Pole is at 90 ° S. South Pole LATITUDES Horizontal lines drawn on a globe or a map are called lines of latitude.  Since these lines run parallel to each other they are called parallels of latitudes.  The latitude of a place on the Earth's surface is its angular distance in the north or in the south of the equator.  It is measured as an angle subtended at the center of the earth.  The latitudes are always expressed in degrees.  They are numbered from 0 to 90 ° North and South.  Equator is located at 0 ". Each degree of latitude is divided into 60 minutes and a minute is further sub - divided into 60 seconds. Suppose the latitude of a place is 8 degrees 4 minutes and 25 seconds, we can express it as 8 '.  , 4,25

Page 22 The lines of latitude are the imaginary lines which encircle the earth. All of them are parallel to the equator, all places having the same value of latitude  to the north or the south of the equator lice on the same latitude For example, 30 * N latitude line joins all places located at an angular distance of 30% north of the equator. The equator, beling in the middle Salong the North Pole 90  'N of the two poles of the earth is the longest line of latitude. Its length is equal to the circumference of the earth which is about 40,075.16 km As we move away from the equator, the circumference of equator the circle decreases. The two poles  are, however, only points. While writing the parallels of latitudes, it is essential to write letter Nor S with them. Letter 'N' is written with the latitudes of the Northern Hemisphere and 'S' with the latitudes of the Southern Hemisphere.  For example, Kerala (in India  ) is located 90'S between 8 ° 18'N to 12 48'N of equator.  CED Parallels of Latitude The Trumber of latitudes, when drawn at 1 'interval, are 90 in the Northern Hemisphere and 90 in the Southern Hemisphere.  The latitude of the equator is 0 ". Besides the equator and two poles, other important lines of latitude are: Tropic ol Cancer 1. The Tropic of Cancer (23% 'N) - It lies north of the equator in the Northen Hemisphere.  234 2. The Tropic of Capricorn (23 / S) - It is located south of the equator in the Southern Hemisphere. Tropic of Capricom 3. The Arctic Circle (66) N) - This important line of latitude is above the Tropic of Cancer  in the Northern Hemisphere, 4. The Antarctic Circle (66% 'S) - It is below the Tropic of Capricorn in the Southern Hemisphere. Important Lines of Latitude HEAT ZONES North Pole 90'N 66% N Arctic Circle 23H'N 56%  09 Equator 23'S Antarctic Circle 66Y'S South Pole 90'S Some parts of the earth receive more heat than other parts because of the variation in the angle of the rays of the sun. Depending on the heat received, the zones are named differently these are - Torrid Zone  , Temperate Zone and Frigid Zone. Let us discuss them one by one  .  The Torrid Zone The Tropic of Cancer and the Tropic of Capricorn mark the limits of this zone.  In this zone, the rays of the sun are exactly overhead once a year except on the equator, where the mid-day sun is overhead twice a year.  Hence, it receives maximum heat from the sun and is very hot.

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The Temperate Zone The zone between the Tropic of Cancer and the Arctic Circle is called the North Temperate Zone.  The zone between the Tropic of Capricorn and the Antarctic Circle is called the South Temperate Zone.  The sun rays in both these zones are never directly overhead.  The angle of the sun rays decreases as we go ww towards the poles.  That is way these zones are neither very hot nor very cold.  They have moderate temperature.  The Frigid Zone The Heat Zones It lies from Arctic Circle to the North Pole and from Antarctic Circle to the South Pole.  This zor remains covered with ice and snow for the most part of the year because the rays of the sun a always slanting.  Hence, it is the coldest zone of the earth.  LONGITUDES 5 The meridians of longitude are a set of imaginary vertical lines.  They are in the form of semi-circles which converge towards the two poles and are the widest at the equator.  Unlike the parallels of latitudes, they are all equal in length.  West The lines of longitudes are drawn all around the globe at an interval of an angle of 1 '.  As all these lines of longitudes are equal, one particular line of longitude was to be selected SAL for numbering them.  The line of longitude passing through the British Royal Observatory at Greenwich, London, has been adopted as the Prime Meridian or Longitude There are 180 ° longitudes each drawn on both sides of Longitudes the Prime Meridian.  The value of the meridians of longitude starts from 19 to 180 ° towards the e as well as towards the west side of the Prime Meridian.  The half part of the earth on the east to Prime Meridian is called Eastern Hemisphere and the other half to the west is called the West Hemisphere.  Thus, in each hemisphere there are 180 longitudes.  The total number of longitude thus, 360. Meridians to the east of Prime Meridian are marked as 'E', whereas to the west of Pri Meridian as 'W'.  However, 180 ° is a common line and form International date line in the Pa Ocean.

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GRID SYSTEM A network of the lines of latitude and North Pole longitude intersecting each other is called a Grid.  Each place on the globe is intersected by vertical and horizontal lines.  Thus, with the help equator of these two sets of lines or the grid system the location of any place can be determined.  For Primo Meridian example, Nasik in Maharashtra is located at an intersection of 20'N parallel of latitude and 74'E South Pole line of longitude Grid of Parallels and Meridians 

LONGITUDE AND TIME In ancient times, changing seasohs, day and night and  position of the sun were some of the means to estimate time.  People observed the path of the sun in DE the sky to estimate the time.  The earth, as we know, rotates from west to east and completes one rotation in 24 hours.  This also means that 360 longitudes face V the mid - day sun one after the other in 24 hours, thus, (15 longitudes pass before the sun in a period of one hour or 60 minutes. Further, it takes 4 minutes for one Sundial with  time longitude to cross before the sun. All the places located on the same meridian have the same local time. The local time of one meridian differs from the other. If it is noon or 12.00 o'clock at Greenwich, 

Do You Know? 

the  local time of all places at 30 ° E longitude will be In Latin am means ante meridian 30 x 4 (minutes) = 120 minutes or 2 hours ahead. It means and pm means post meridian. the time on 30º E will be 12 + 2  = 2.00 pm On the other hand, the local time of all places at 30 ° W longitude will be 2 hours behind the Greenwich time. It will be 12 - 2 = 10.00 am Thus, the local time will be ahead at all the places in  the east of a given meridian and it will be behind at all places in the west of a given meridian. 

STANDARD TIME We  know that places located on different meridians have different local time.  It would create a lot of difficulties, if all countries would adopt different local time.  The railway time - table and the

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schedules of the air flights would be difficult to prepare.  People crossing the longitudes would have to adjust their watches.  India lies between 68% E and 97'25 'E longitudes.  Think about the problems, the people of India would face if they follow the different local times.  (In order to avoid this problem and maintain its uniformity all over a country, it was decided to adopt the local time of a central meridian of a country as the Standard Time of India mostly the meridian selected, is divisible by 7 ° 30 'so  that the difference Jantar Mantar Jaipur between its standard time and the Greenwich Mean Time (GMT) is expressed in the multiple half an hour '. The meridian, selected for a country, is called the Standard Meridian. 

Do you know? Some countries have a  vast longitudinal extent. That is why countries like Russia has nin and USA has four time zones. 

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(India, spanning roughly over 30 "longitudes, has selected 82 ° 30 'E longitude as its Standard Meridian. It passes through a place near Mirzapur. Its local time is taken as the Indian Standard Time (IST). The Greenwich Mean Time (  GMT) is 5% hours behind the Indian Standard Time. Greenwich Mean Time is followed by all countries for the international airlines and ship fleets, 

Do you know? Although, about 30 longitudes pass over India, yet it has only one standard meridian and  one standard time for the whole country for convenience. This is called Indian Standard Time (IST). Keywords schedule: it is a plan for carrying out a process or procedure. subtended: form an angle at a particular point. variation: it is a  slight difference in condition or amount in certain limits.