Latitude & longitude

Latitude & Longitude : Created by Puja Chowdhury (Basu) 1 Latitude & Longitude by Puja Chowdhury (Basu) basu.puja@gmail.com

Importance of Latitude & Longitude : Created by Puja Chowdhury (Basu) 2 Importance of Latitude & Longitude Mapping is a key technique for depicting geographical information. Maps are two-dimensional representations of three-dimensional surfaces. Common coordinate system used to locate points is Latitude and Longitude. The positions of objects on the earth's spherical surface are measured using latitude and longitude. Latitude and longitude are two of the most basics terms in all of geography.

What is longitude? : Created by Puja Chowdhury (Basu) 3 What is longitude? lines running north and south around the globe think of Earth as a globe think of the globe as divided into lots of little sections a circle has 360 degrees that's true for Earth as well

Contd… : Created by Puja Chowdhury (Basu) 4 Contd… If you put your finger on the city of Paris and trace all the way around the globe, from right to left, you will trace the full 360 degrees. Go just halfway and you get 180 degrees

Contd… : Created by Puja Chowdhury (Basu) 5 Contd… You have just traced 360 degrees of longitude Longitude are lines that run north and south The Prime Meridian, in Greenwich, England, is at 0 degrees longitude

What is latitude ? : Created by Puja Chowdhury (Basu) 6 What is latitude ? lines running east and west around the globe Put your finger on Paris again Trace around the globe, this time going around the top of the globe, then around the bottom, and back to Paris

Contd… : Created by Puja Chowdhury (Basu) 7 Contd… You've just traced the full 180 degrees of latitude Latitude is only 180 degrees Latitude lines run east and west and measure north or south The Equator is at 0 degrees latitude

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Contd… : Created by Puja Chowdhury (Basu) 9 Contd… you want to tell your friend exactly where Paris is So check out a map that has latitude and longitude marked on it You'll find that the latitude and longitude markings are every 10 degrees. (Some maps have markings for every 15 degrees or even every 5 degrees.)

Contd… : Created by Puja Chowdhury (Basu) 10 Contd… Paris is almost halfway between 45 degrees and 50 degrees markings It's probably about 47.5 degrees. Let's call it 48. That's latitude

Contd.. : Created by Puja Chowdhury (Basu) 11 Contd.. What about longitude? the Prime Meridian is at 0 degrees. That's in England France is just east of England Paris is just less than halfway between the 0 degrees and 5 degrees markings It's probably about 2 degrees

Contd… : Created by Puja Chowdhury (Basu) 12 Contd… what is the exact location of Paris Paris is indeed at 48 degrees north and 2 degrees east

World Map with Latitude & Longitude : Created by Puja Chowdhury (Basu) 13 World Map with Latitude & Longitude

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How to measure Latitude & Longitude? : Created by Puja Chowdhury (Basu) 15 How to measure Latitude & Longitude? Latitude & Longitude are called geographic coordinates and are expressed in angular units (degrees and minutes or decimal degrees) Latitude is measured as degrees north or south of the equator (the equator is 0º) Latitude numbers start at 0 at the equator and become larger as you go toward each pole S latitude is sometimes expressed as negative degrees (e.g. -51° = 51°S)

Contd… : Created by Puja Chowdhury (Basu) 16 Contd… Longitude is at 0 at the Greenwich Meridian and increases as you go towards E or W W longitude is sometimes expressed as negative degrees (e.g. Calgary is at -114° or 114°W

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Limitation of Latitude & Longitude : Created by Puja Chowdhury (Basu) 18 Limitation of Latitude & Longitude Latitude and longitude can locate exact positions on the surface of the earth, but they are not uniform units of measure only along the equator does the distance represented by one degree of longitude approximate the distance represented by one degree of latitude If you look on a globe of the earth, you will see the longitude lines are closer together as you move further north or south of the equator This familiar system is best to use with maps showing a large area. Latitude and longitude coordinates are indicated along the borders of topographic maps

Heat Zones : Created by Puja Chowdhury (Basu) 19 Heat Zones The earth receives its heat energy from the Sun Prevailing temperature of a place on the surface of the earth depends on the amount of heat energy received from the Sun The heat energy thus received is not uniformly distributed over the surface of the earth The differences in the distribution of temperatures are mainly due to the variation in the angle of incidence of Sun’s rays on the earth and the shape of the earth.

Angle of the Sun’s rays : Created by Puja Chowdhury (Basu) 20 Angle of the Sun’s rays The amount of heat received by the surface of the earth depends on the angle at which the rays of the Sun fall on that surface the vertical rays heat a small surface whereas the inclined rays heat relatively a larger surface We all know that at noon the temperature is very high and it is very hot. This is primarily because the Sun’s rays fall vertically on the earth. When we go for a walk in the morning or evening, we feel the temperature is very mild. It is because the Sun’s rays falling on the earth at an inclined angle

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Contd.. : Created by Puja Chowdhury (Basu) 22 Contd.. The Sun’s rays do not fall on the spherical earth at the same angle. The rays of the Sun fall directly on those parts that are vertically below the Sun The angle of the Sun’s rays increases falling on either side of those parts that are vertically below the Sun The vertical rays of the Sun heat only a smaller area on the earth and thus the heat energy received by that area is also very high

Contd… : Created by Puja Chowdhury (Basu) 23 Contd… But the same amount of Sun’s rays when falling at an angle on the surface of the earth has to heat relatively a larger area The heat energy is distributed over a larger area. So, the heat energy received by that surface is also relatively very low. The surface of the earth is divided into different heat zones based on the difference in heat energy received in different places

Contd.. : Created by Puja Chowdhury (Basu) 24 Contd.. 3 different types Heat Zones The Torrid Zone The Temperate Zone The Frigid Zone

The Torrid Zone : Created by Puja Chowdhury (Basu) 25 The Torrid Zone The earth surface lying in between the Tropic of Cancer (23 ½ °N) and Tropic of Capricorn (23 ½ °S) is called “Torrid Zone”. The Sun’s rays fall vertically over this surface almost throughout the year. Therefore very high temperature prevails during summer and mild temperature during winter

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The Temperate Zone : Created by Puja Chowdhury (Basu) 27 The Temperate Zone The earth surface lying between 23½° N and 66½° N latitudes in the Northern Hemisphere and 23 ½ ° S and 66 ½ ° S latitudes in the Southern Hemisphere is called “Temperate Zones”. The Sun’s rays fall at an inclined angle over this surface throughout the year. Therefore mild temperature prevails in this zone throughout the year.

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The Frigid Zone : Created by Puja Chowdhury (Basu) 29 The Frigid Zone The earth surface lying in between the Temperate Zone (66 ½ ° N.) and North Pole (90° N.) in the northern hemisphere, and the temperate zone (66 ½ ° S.) and the South Pole (90° S.) in the southern hemisphere is called “Frigid Zone”. The Sun’s rays are falling very oblique throughout the year. Therefore very low temperature prevails throughout the year.

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The Time Zones : Created by Puja Chowdhury (Basu) 32 The Time Zones The rotation of the earth on its axis is the cause for the occurrence of the day and the night A day is equivalent to 24 hours. A whole day is divided into 12 hours of daytime and 12 hours of night time The earth takes as much as 24 hours to complete one rotation on its axis. The 360 longitudes on the globe also take as much as 24 hours to complete one rotation (24 x 60 =1440 minutes). Then what is the time taken to cross one longitude? Four minutes (1440 m / 3600 long. = 4 m.) is needed to cross one longitude (10) on the globe. (m = minutes)

Contd.. : Created by Puja Chowdhury (Basu) 33 Contd.. Let us assume that the Sun rises at 5 a.m. in India and the people living in Arunachal Pradesh, on 97° E longitude will see the Sunrise at that time. If so, at what time the Sun will rise on 68° E longitude, which passes through in the state of Gujarat which is situated around 68° E longitude. In India there are 29 longitudes running in between Arunachal Pradesh and Gujarat. The time taken to cross one longitude is four minutes and therefore 1 hour and 56minutes will be taken to cross all the 29 longitudes. In Arunachal Pradesh, if the Sun rises at 5 a.m. then in Gujarat the Sun will rise only after 1hour and 56 minutes.

Indian Standard Time : Created by Puja Chowdhury (Basu) 34 Indian Standard Time The central meridian that runs across a country is the basis for calculating the standard time of that country The 82° 30’ is the central meridian of India. When the Sun is directly on this longitude, the time in India is 12 Noon. This time is assumed as the standard time of India. Similarly in the world every nation has adopted a central meridian and follows the time on that basis. Big countries adopt more than one standard time. India extends from 68°E longitude to 97°E longitude. Therefore 82° 30’ Longitude is taken as the central meridian in India. (68°E longitude + 97°E longitude = 165/2 = 82°30’E. longitude)

World Standard Time : Created by Puja Chowdhury (Basu) 35 World Standard Time There are 360 longitudes drawn on the Globe The central meridian is the Greenwich Meridian (0° long.) When the Sun shines directly on this longitude it is taken as 12Noon and it is considered as World Standard Time.

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Calculating the Time using Longitudes : Created by Puja Chowdhury (Basu) 37 Calculating the Time using Longitudes

Contd.. : Created by Puja Chowdhury (Basu) 38 Contd.. Let us understand how the world time is calculated with reference to the longitudes In the figure, three places, namely, a, b and c are marked and the directions are also shown Let us assume that the time difference between place ‘a’ and ‘b’ is 1 hour. If the time at place ‘b’ is 6 in the morning, then the time at place ‘a’ is 5 in the morning and time at place ‘c’ is 7 in the morning. The time at place ‘a’ is 1 hour less than the time at place ‘b’ because place ‘a’ is located to the west of place ‘b’.

Contd.. : Created by Puja Chowdhury (Basu) 39 Contd.. Likewise, because place ‘c’ is east of place ‘b’ and so the time at place ‘c’ is 1 hour more than the time at place ‘b’. This is due to the fact that the earth rotates from west to east. As place ‘c’ is east of places ‘a’ and ‘b’, the Sun rises first and the time is 7 a.m. while it is 6 a.m. at place ‘b’ and 5 a.m. at place ‘a’. It is clear that the time decreases as we go west from Greenwich and increases as we go east from Greenwich.

Slide 40 : Created by Puja Chowdhury (Basu) 40 Thank You!