4. Latitude and Longitude

Define latitude and longitude and use them to locate places on Earth

We know that a globe is a spherical model of the earth. When we look closely at the globe, we see horizontal and vertical lines crossing each other. These lines are called latitude and longitude. These two sets of lines that cross each other help in finding any location on the Earth.

Latitudes are imaginary horizontal lines running east to west, circling the earth. These are also called parallels because they run side by side and never meet.2

Fig 4.1: Latitude, also known as parallel

There are a total of 181 latitudes including the equator. They are numbered from 0° to 90° North in the Northern Hemisphere and from 0° to 90° South in the Southern Hemisphere.2

1. Important Latitudes

Fig 4.2: Important Latitudes

a. The Equator

The Equator, which is also known as the great circle, is the largest latitude that divides the earth into two equal halves. The half to the north is called the Northern Hemisphere and the half to the south is called the Southern Hemisphere.3

b. The Tropic of Cancer

Located at the angular distance of 23 ½° north of the equator, The Tropic of Cancer marks the farthest point north where the Sun's rays can shine directly overhead at some point during the year.3

c. The Tropic of Capricorn

Located at the angular distance of 23 ½° south of the equator, The Tropic of Capricorn marks the farthest point south where the Sun's rays can shine directly overhead at some point during the year.3

d. The Arctic Circle

The Arctic Circle is located in the Northern Hemisphere, at a distance of 66 ½ ° north of the equator, beyond the Tropic of Cancer. It marks the limits of the North Polar area that surrounds the North Pole.3

e. The Antarctic Circle

The Antarctic Circle is located in the Southern Hemisphere, at the distance of 66 ½ ° south of the equator, below the Tropic of Capricorn. It marks the limits of the South Polar area that surrounds the South Pole.3

f. The North Pole

The North pole lies at the distance of 90° North of the equator. It marks the northmost point of the earth.3

g. The South Pole

The south pole lies at the distance of 90° South of the equator. It marks the southernmost point of the earth.3

The set of imaginary lines running vertically from the North Pole to the South Pole are called longitudes. All longitudes are equal in length and meet at the poles, unlike latitudes, which remain the same distance apart.

There are a total of 360 lines of longitudes i.e. 180 to west and 180 to the east of the Prime Meridian. Longitudes meet at the pole and thus are not parallel to each other.4

Fig 4.3: Longitudes also known as meridians

Special Longitudes

There are two special longitudes:

1. Prime Meridian

The longitude that passes through Greenwich (in London) is called the Prime Meridian. It is marked as 0°. It divides the Earth into two equal halves - The Eastern hemisphere and the western hemisphere.5

Fig 4.4: Prime Meridian

2. International Date Line (IDL)

The 180° E and 180° W longitudes fall on the same line, which is exactly opposite to the Prime Meridian. This line is called the
IDL - International Date Line. When we cross the International Date Line from west to east we lose a day and when we cross the line from east to west we gain a day6.

Fig 4.5: International Date Line

Vid 4.1 latitudes and longitudes

Comparing latitude and longitude7.

Latitudes and longitudes form a network of lines on the globe called a grid. This grid is used to locate places on the globe. To find a location, we must know its latitude and longitude. The point at which the latitude and longitude lines intersect is the location of the place.8

Fig. 4.6 - Grid

Vid 4.2: How to locate a place using latitude and longitude?

Latitude and longitude provide a way for us to understand and communicate the locations of different places on Earth.
Latitude and longitude are essential for reading and interpreting maps.
It helps us discover how time changes as one moves east or west across different longitudes, and how this affects time differences between different regions.

Glossary

hemisphere: half of the Earth; either the Northern, Southern, Eastern, or Western half
time zone: a region where everyone uses the same standard time, helping us keep track of time in different parts of the world
parallel: lines that go side by side and never meet, like lines of latitude on a map
farthest: the most distant point
circling: moving around something in a round path
pole: the northernmost or southernmost point on Earth (North Pole or South Pole)
coordinates: numbers that help us find a specific location on Earth
locate: to find where something is
interpret: to understand or explain the meaning of something
essential: very important

Summary:

Latitudes are imaginary horizontal lines running east to west, circling the earth. There are a total of 181 latitudes including the equator.
There are seven important lines of Latitude -

1. Equator (Latitude 0o)

2. Tropic of Cancer (Latitude 23.5oN)

3. Tropic of Capricorn (Latitude 23.5oS)

4. Arctic Circle (Latitude 66.5oN)

5. Antarctic Circle (Latitude 66.5oS)

6. North Pole (Latitude 90oN)

7. South Pole (Latitude 90oS)

The set of imaginary lines running vertically from north pole to south pole are called longitudes. There are a total of 360 longitudes.
The longitude that passes through Greenwich (in London) is called the Prime Meridian. At 180° E and 180° E falls the International Date Line.
The latitude and longitude form a network of lines on the globe. This is called a grid. A grid helps to locate a place.