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Latitudes and Longitudes
US
SYLAR Grid : Latitudes ‘and Longitudes
hic i i
Gee ence ‘of latitudes : main latitudes, their location with degrees,
Parallels of latitude and their uses,
Constr of longitudes : Prime Merion, time (ocal,sordard ond
(8) Concept and Inleational Dato Line (IU). Easier ond Wanenm®20e#) Greenwich Mean
"sphere
Using latitudes and longitudes to find location
)
Calculation of time.
(6) Great Circles ond their vse
OUTLINE OF THE CHAPTER
subunits - 1. Introduction ~ itech Gi Sen
3. Lattudes “4, The main five Parallel of Latitudes
6. The concept of Longitudes
8. Calculation of Longitude and Time
5. The Climatic Zones of the Earth
= 10, World Time Zones.
7. The Great Circle routes
49, International Date Line
1. INTRODUCTION
The shape of the earth and its hemispheres
«s Earth's spherical shape is best represented by
a globe. The earth is flattened at the poles and
slightly bulged at the equator. Centrifugal force
and gravity are responsible for its shape. It is
‘an oblate spheroid in shape and is called the
Geoid.
Earth is the only planet with life on it, with a
vast equatorial circumference of approximately
40,075 km.
To find the exact location of the place on the
lobe, one has to use a map with a network of
parallels of latitude and meridians of longitudes
known as the earths grid.
‘+ The earth is divided into four hemispheres.
The regions north and south of the equator (0°)
are called Northern Hemisphere and Southern
Hemisphere respectively.
Northern and Souther
Hemispheres
North & south
cf the equator
+ The region east and west of the prime meridian 7 :
© end (180°) longitude is called Eastern The four main directions — north, south, west
femisphere and Western Hemisphere. ‘and cast are called the cardinal points which are
A Textbook of ICSE Geography Class. eee EE (-———————— A Textbook of ICSE Geography Clay A. The shortest distance between i
| the earth’s surface is the Are pea
{ which passes through two points X and Y.
For example, the shortest distance between
Cape Town and Buenos Aires is not the 35° §
parallel of latitude which passes through both
of them, but the are of Great Circle Are AB
which is drawn between these two points,
3. The shortest distance between Madrid and
Beijing is not the 40° N Latitude, but the Great
circle Are—XY drawn between these two points,
Importance of Great Circle Routes
(a) Since great circle routes are the shortest
distance between the two places on the Earth
and lie on the arc of a Great Circle they are
used mainly to save fuel and time, as it is very
economical.
(b) Hence, it is most advantageous for aircrafts,
over the North Polar regions.
(©) Sailors on the sea also use it wherever it is
possible and as long as it does not lead them
into unsafe waters. For example, sailors cannot
use them in Arctic and Antarctic regions
because of frozen seas and unsafe travel.
8, CALCULATION OF LONGITUDE AND TIME
‘+ One can imagine the pandemonium if there was
ro system of time. The world communication
and working would have come to a standstill.
+ On the other hand, if each town, village
and city in the world had kept its own time
aused utter confusion. aS
ches would have (0 be
is one travelled from one
it would have
the clocks: and Ww
constantly altered
place to another. ,
+ Hence, to solve this problem G
Mean Time (GMT) is taken as reference for
international time.
+ Time is added to GMT while travelling
towards cast of Prime Meridian and deducted
while travelling west of Prime Meridian.
Greenwich Mean Time (GMT)
The zero degree meridian passes through the
Royal Astronomical Observatory at Greenwich
village, near London, Its called Prime Meridian.
+ In 1884, it was decided by international
agreement to adopt the local time of Prime
Meridian (0°) worldwide, by all countries and
international airlines.
+ Hence, when sun is directly overhead at 0°
longitude and it is 12 o'elock (noon) there, the
international time is calculated cast or west of
the Prime Meridian with reference to this tim
* Since the earth rotates west to cast, the places
situated toward the cast of Prime Meridian
will have evening while places to the west
will be having moming, when it is noon at
the prime meridian,
To find local time with the help of longitudes
(i) We know that the earth is spherical in shape
and 360 longitudes are imaginary lines drawn
from north to south, 1° apart on the Equator,
The earth completes one rotation on its axis
in approximately 24 hours.
The earth takes 24 hours to run through 360
degrees. The Sun appears to move at the rate
of 15° in 1 hour (60 minutes) or 360° in 24
hours or 1° in 4 minutes.
+ Therefore, one can say Sun is overhead
ian after 4 minutes. It is noon
es on that longitude when Sun is
overhead and it is known as local time of
that longitude.
Local Time and Standard Time
Local time
+ The local time of a place can be calculated
if we know the longitude of the place.
nwich
(ii)
(iii)
A Textbook of ICSE Geography Class IX > + We can understand this concept by the
following examples—
To find local time when we know the longitude —
Example 1. If the GMT at 0° longitude is
12 noon, find the local time at station A and B.
At station A
The difference in longitude between 0° and
station A is 60° towards east.
* Since it is 12 o°clock at 0°, the difference of
time between A and 0° will be 60 x 4 = 240
minutes or 4hours.
+ AsA js located to the east, it will be 4 hours
ahead of Greenwich time : 12+ 4 = 16 hr.
or 4 pm.
‘+ Therefore time at station A will be 4 pm.
At place B
The difference in longitude between 0° and
station B is 30° towards west.
« The difference of time between B and 0° will
be 30 x 4 = 120 minutes or 2 hours.
+ Since B is situated to the west of prime
meridian, the local time at B will be 12 - 2
hours = 10 am.
+ ()) Tropic of Cancer, 23%" N, passes through the
FOUR points A B C D, dividing India into two
halves : North Temperate and South Tropical
Standard Time and Time Zones
If each city were to Keep the time op
meridian, there would be much differenes io
time between one city and another, ‘The,
em of standard time is observed by gy tire ©
Most countries adopt their standard yc tig
focal time of their central meridian, Fay "Ye
India follows the loca ime ofits cent “hl
82/28, which passes through Allahays ey
+ Generally, the standard meridian of 4
is taken as multiple of 15° or qy0 Coun
the difference of time between Gygp tha
standard time of that country js ae th
a multiple of one hour or half an hou, "43s
«For example, the Indian Standard Tine
is 5 hours 30 minutes ahead of Gyr’ (80)
and Sri Lanka being close to India, follo pal
same time. the
‘a
syst
B_ Greenwich A
j time at 60° E and 30° W
A Textbook of ICSE Geography Class g, INTERNATIONAL DATE LINE
The history of the International Date Line dates
pack to the Christian era 1522, when Magellan's crew
reached home after circumnavigating the world for
the first time by ship. They thought it was Sth
September but actually they reached on 6th September,
This is because a peculiar situation arises at the
Meridian 180°,
« This meridian may be reckoned both as 180°E
and 180° W.
« International Date Line or IDL is a line
concemed with the dates of the calendar and
adopted internationally,
+ It is taken as 180° meridian, It passes through
the middle of the Pacific Ocean,
« When we travel east of this line it is referred to
as 180°E and when we travel west of this line
it is referred to as 180° W,
+ On either of this line, a difference of one
whole day is observed. This is because the earth
completes one rotation on its axis in 24 hrs. as
it moves from west to cast.
For example, suppose we start travelling from 0°
meridian westward, on reaching 180° W, the time
is decreased by 12 hours. Hence at 180° E, the
time is increased by 12 hours, whereas at 180°
meridian there is difference of exactly one day,
+ Therefore, for the convenience of those travelling
round the world, the /nternational Date Line has
meridian, while
25th December
26th December.
to West, it will
in, hence it will
+A ship crossing the 180°
travelling from west (0 east on
will add one day, Le. it will be
whereas crossing from East
repeat the sume day and date agal
be taken as 25th December. (See Fig, 218)
ase fy
We.
‘South Pole “480th Meridian
Fig 2.16 : Intemational Date Line
+ Meridian 180° was chosen as Intemational Date
Line because it passes through the middle of
the Pacific Ocean and there is practically no
landmass, and wherever there is landmass a
deviation has been taken.
+ Thus, a zigzag line at roughly 180° meridian has
been internationally accepted for rectification of
date and therefore, it is called International Date
been established, Line.
ha
a WEST « > EAST ;
. 74°W 80°E ot
' W.LS4-------]}-———> E.G.A.
(West-Lose-Subtract) (East-Galn-Add) |
|
NEW YORK LONDON CHENNAI)
"Fig, 2.19 + East Gain + Add, West Lose ~ Subtract
A Textbook of ICSE Geography Class IX. co HED foro ielcones which passes through Allahabad Since i fea
‘The world is divided into 24 time zones. Fach Pesce merry EN tt plate
sec Ti a ved lve 24 tine ae Se cen ee ad ies
ed ie Some IST). The ilference Benween the td
Teen ee Ai pas iin Lu tne dt Grech Nene
in fngn or 1 ite ned tine 8 ST (EAH) HRB he 3% hou (Ow Bs
of ther Tongides and §24° x 4 = 330 minutes or 5% hours)
is means that when it is noon at England
(0° longitude), itis $.30 pm in India,
central meridian irrespective
Tocal times.
are ample, in India the fongitude of 824° B ©
(82 30°) is selected as Standard Me
eridian,
Fig.220; Time Zones tine Word
ISA, Canada, Austalia zones. From East to West they are known as Hawaii
‘Time Zone, Alaska Time Zone, Eastern, ‘Central,
‘Mountain and Pacific Time Zones.
‘Some countries such as US
and Russia which have 2 vast East to, West extent
fave several Time Zones. Canada has 6 time zones,
Russia as many as 11 time zones and USA has 6
‘able 21 +A comparison botween te Paras of Latitude and Mertans of Longtide
E Tan
1 ess ut en
ich 0°
{Latitude is the angular distance of a point,
ror or south ofthe equator, a5 measured
in degrees,
2. All latitudes are parallel to the equator,
3, The distance between two latitudes is
approximately 111 km
xn
28, —— F A Textbook of ICSE Geography Class IX
4. The 0 latitude is refer
ne ees
ar tee
|S the tales om
| © Tet denon
1. The four direction
known as the ear
places on the ma
2. Eant’s gd is a
parallel tne Eq
North Pole to &
paricular point +
‘ther at right an
‘8, The horizontal
called latitudes
South Pole are
+ Latitude is
‘ot the Equa
+ Longitude |
of the Prin
4, The lines of
(a) The tines
pole. Thu
Circle. Re
(0) There an
(6) The dis
(approx
\ (6) The
A Textbook of IC The O° latitude is reterred to
are 90° of lati
20° lavtudes South oF the cay
s & The latitudes from eq
used to demarcate tempe
mature zone,
23',°N —
[Direct rays
Thre a 360" f Tonga, 180" cach 6
The ton
foference to the time at prime meridian (GMT)
Temperate
Zone
eS: North Temperate Zone | 6614°N — 90°N (N. frigid Zone)
284°S ~ 66'°S. South Temperate Zone
meridian,
ides are used to determine the time with
6614S ~ 90°S (S. frigid Zone)
Extremely slanting
Climate I Very hot 1
other at right angles,
3. The horizontal lines drawn parallel to the
zs ator
called lattudes and vericallnes trom Note noi
South Pole are called longitudes,
~ Latitude is the angular distance north and south
= Longitude is the angular distance we
of the Prime Meridian (0°) cetera
‘4. The lines of latitude —
(a) The lines of latitudes grow smaller towards the
pole. Thus Equator at (0°) is the only Great
Circle. Rest are all small circles.
(b) There are 181 parallels of latitudes, 90 to the
north and 90 to the south of the Equator where
Equator is taken as 0°.
(©) The distance between each latitude is 111 km
(approx.)
(@) There are five main parallels of latitudes,
Equator (0°), Tropic of Cancer (23%° N). Tropic
‘of Capricom (23%° S), Arctic Circle (66%° N)
Slanting rays
Neither too hot nor too cold
Very cold sl
‘and Antarctic Circle (66%°S).
North Pole and South Pole represent the 90° N
and 90° S in the form of points
(e) Amongst all the latitudes Equator (0°) is the only
‘great circle which divides the Earth into Northem
Hemisphere and Southem Hemisphere.
5. Latitudes along with longitudes enable us to spot
the exact position of a place on the globe.
6. The lines of longitude —
(@) The 0° longitude passing through Greenwich
near London is called the Prime Meridian.
(b) There are 360 meridians of longitude.
(6) All the meridians of the longitude are Great
Circles and divide the Earth into Eastern
Hemisphere and Western Hemisphere.
(d) The distance between any two meridians is not
the same. They come closer towards the Pole.
(e) The longitudes are used for
« locating places on the globe
‘© determining the local time of a place
(f) Greenwich Mean Time (GMT) is the noon
time of the old Greenwich Observatory (0°
longitude). Its time is taken as Standard time
of England and International time.
(g) International Date Line is an imaginary line
along the 180° meridian, extending from Pole
to Pole.
ook of ICSE Geography Class. BY san ipon 908°
porter and Sauer Heroes
soning i cra
Mind Map 2.2 GMT and IST
ont
Greenwich Mean Tr
0" longitude
Greenwich
‘othe entire world
Indian Stands
tard Time
only india
TECHNICAL TERMS TO REMEMBER nnn
‘Time zones : Zones or belts of given east-west (longitudinal) Longitude : The angular distance of a place castor wes
went within which standard time is applied according of the ‘Prime Meridian.
to a uniform system. a : Prime Meridian : The longitude of zero degree passing
earth's grid : A network of latitudes and longitudes on yhrough Greenwich near London!
the Earih’s surface to find the exact location of a place.
‘Axis : An imaginary line joining the North Pole and South
Pole on which the Earth rotates.
Latitude : An angular distance of a point on the Earth's
Meridians
Great Circle : A circle that divides the Earth into wo
equal halves.
Semi-circles connecting the north and south.
surface from the centre of the Earth. International Date Line : The Meridian of 180°.
EXERCISE
5.
‘A. Answer the following questions briefly :
1. Why do we need to locate places on Earth?
°
2. What do you mean by the latitude of a place?
3. What is meant by Prime Meridian?
x
4, Explain why there is no higher latitude
le oth
90 degrees North and South, eis
a
Explain why Lines of Longitudes are called Merian
of Longitude.
State two properties of the Lines of Latitude.
State two properties of Lines of Longitude.
8. The distance between two successive pale 4
latitudes is 111 km. Explain.
What are the limits of two Temperate Zones?
“ATextbook of ICSE Geography Cas! 10.
or
12.
13.
14.
15.
16.
7.
18.
19.
20.
21.
23.
24.
26.
27.
Why are the places in the Torrid Zone hotter than
those in other zones?
Why are the places in the Frigid Zone colder than
in other zones?
How is the Local Time of a place fixed?
{sit correct to say that Local Time is the Sun Time?
I the GMT at 0° longitude is 12 noon, find the local
time of place A (30°E)..
‘Why is the Standard Time considered necessary?
What are Time Zones? How many Time Zones do
we have?
London experiences a lower temperature than
Singapore throughout the year. Why?
What is Intemational Date Line? Describe the use
of this line.
Why do some countries have many Time Zones?
What are Small Circles?
Except for the Equator, other Parallels of Latitudes
are not Great Circles. Why?
How is the use of local time inconvenient in practical
lite?
What is a Grid?
Who was the first mathematician to have measured
the circumference of the Earth?
. Name the important Climatic Zones of the World.
State the rate of change of time with longitude.
Explain how latitudes and longitudes help to locate
Position of a place on a globe.
is the latitude of place X?
(a) Local Time and Standard Time
(0) Parallels and Meridians
(c) Equator and Prime Meridian
B. Define the following terms :
1. Latitude 2 Longhude
3. Meridian 4. Prime Meridian
5, Local Time ane
7. Indian Standard Time 8. Greenwich Mean Time
9, Intemational Date Line 10. Great Greie
11, Small Cirle ees
C. Distinguish between the following pairs :
4. Latitude and Longitude.
2. Great Circle and Small Circle.
3. Greenwich Mean Time and Indian Standard Time.
D. Give reasons for the following :
4. Latitudes and Longitudes are always expressed in
angles.
2. Large countries have many time zones.
3. The Intemational Date Line is not a straight fine like
other longitudes.
4. A person gains time as he travels towards east.
5. The intervals between successive parallels are
constant.
6. A person travelling trom Mumbai to London has to
alter his watch.
7. The difference between |
8. Parallels are not equal in length. ;
9. Navigators use Great circle route for navigation.
E. Draw a neat diagram to show the following
1, Parallels of Latitude
2. Temperature Zones
3 Earth's Grid
Choose the correct option :
1. Earth is divided into Northern & Southern
Hemisphere by which of the following imaginary
tine?
(a) Prime Meridian (b) Tropic of Gancer
(©) Equator (4) International Date Line
2. What is the latitude of Arctic Circle?
(a) 66%°S (0) 23%°S
(c) 66%°N (a) 23%°N
3. How Many total lines of latitudes are there in the
world?
(a) 90 (bo) 91
(©) 180 (@) 181
eS 4. Rotor to the Imago and identity the climatio zone
‘of the shaded region,
Tropical of Capcom
(b)_ Noxth Temperate Zone
(a) South Frigid Zono
__ for overy 1°
(a) North Frigid Zono
(0) Torrid Zone
5, Thoro is a time difference of __
of longitudinal ditterence.
(a) 2 minutos (0) 4 minutes
(6) hour (d) 60 seconds
6, What Is tho full form of IDL?
(a) Intemational Diagonal ine
(0) Informal Dotour Line
(6) Intemational Dato Line
(d)_Intormediate Diagonal Lino
7. Which of tho following meridian Is called tho
Contral Moridian of India?
(a) 83%" W (0) 0
(©) 82° E () 726
8. USA has time zones.
(a) 8 ) 1
6 (7
Ss
18, Which of tha following alatements ralated to tings
‘of latitude In not corract?
(a), Thay aro called paraliols of Latitud
(0). Thay aro uned to dotarmine timo,
(0). Thoy are important to dotermine climate,
(a) Equator is the largest tine of tatude,
10, Moridian moans
(a). Midnight (b) Midday
(6) Morning (d) Dusk
14, Tho difforonco botwaon IST & GMT is,
(a) 6 houre (b) 4 hours 30 minutos
(6) Ghours 3omins — () 12 houre
12, Which of the following statomont about Groa,
citclo Is tru0?
(a) Alltho paratiols are Groat circ
(b)_ Navigators find It dificult to folk
Groat crcl. ee
(c) Equator & all tho meridians are Great circles,
(d) All the above.
13, World Is divided into
(a) 20
© 1
ANSWERS
1 20 3 46) 5.0)
6 (c) 7% (6) 8) 9. (&) 10. (6)
140) 12) 13, @)
oe
| Textbook of ICSE Geography Class IX
