Latitude and Longitude – Important Parallels and Meridians

At a Glance

• Latitude Angular distance north or south of the equator, 0° to 90°
• Longitude Angular distance east or west of Greenwich, 0° to 180°
• Important parallels Equator, two Tropics, two Polar Circles
• Heat zones Torrid, temperate and frigid
• Time link 15° of longitude equals one hour
• Exam link UPSC Prelims, Geography: Earth’s Origin, Interior and Motions

Where Does It Fit?

This topic supplies the grid of parallels and meridians that the rest of the macro uses. The reference lines described here are needed for the later topics on seasons, time zones, climate zones and India’s location. Previous topic: Pangaea, about 300 to…">Geological History of the Earth. Next topic: Motions of the Earth: Rotation and Revolution and Their Effects.

What Is Latitude?

In short: latitude tells how far a place lies north or south of the equator.

Latitudes and longitudes are imaginary lines that make a coordinate system. They are used to fix the location of any place on the Earth; for example, New Delhi lies at about 28 degrees north latitude and 77 degrees east longitude. Latitude is the angular distance of a place north or south of the equator, measured in degrees from the centre of the Earth. The equator is the zero line, so latitude runs from 0 degrees at the equator to 90 degrees at each pole. Places north of the equator carry the suffix N and places south of it the suffix S. Lines joining all places with the same latitude are called parallels of latitude, because they run parallel to the equator and never meet. The equator is the longest parallel, and parallels become shorter towards the poles, where they shrink to points.

How Long Is a Degree of Latitude?

Because the Earth is slightly flattened at the poles, a degree of latitude is not exactly the same length everywhere. At the equator one degree of latitude is about 110.57 km, at 45 degrees it is about 111.13 km, and at the poles it is about 111.7 km. For convenience an average of about 111 km is used, which is why distances north and south can be found quickly by counting degrees.

Which Are the Important Parallels of Latitude?

Besides the equator (0 degrees), the North Pole (90 degrees N) and the South Pole (90 degrees S), four parallels are important. Each marks a change in how the Sun’s rays strike the Earth through the year.

The Tropic of Cancer passes through eight Indian states: Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand, West Bengal, Tripura and Mizoram. It divides India almost into two halves, with the northern part in the subtropical zone and the southern part in the tropical zone.

What Are the Heat Zones of the Earth?

The Earth’s parallels divide it into three heat zones, according to how the midday Sun’s rays reach the surface.

Temperature falls as one moves from the equator towards the poles because the Earth is a sphere: the equator receives direct sunlight, while the rays become oblique towards the poles and the energy received per unit area decreases. This is a key idea behind the topics on temperature distribution later in the subject.

What Is the Latitudinal Extent of India?

The mainland of India extends from about 8 degrees 4 minutes N to 37 degrees 6 minutes N latitude. The southernmost point of the country, Indira Point in the Great Nicobar Island, lies at about 6 degrees 45 minutes N. The latitudinal extent is therefore about 29 degrees from Kanyakumari to the north of Kashmir, and the distance from north to south on the mainland is about 3,200 km. Because the Tropic of Cancer cuts through the country, India has both tropical and subtropical regions, which helps explain the variety of its climate.

As an analytical point, latitude is the first and most direct control on climate, because it decides how much solar energy a place receives; later controls such as altitude, ocean currents and distance from the sea modify this basic pattern.

What Is Longitude?

In short: longitude tells how far east or west a place is from the Prime Meridian.

Longitude is the angular distance of a place east or west of the Prime (First) Meridian, measured in degrees from the centre of the Earth. On a globe, longitude is shown as a series of semicircles that run from pole to pole through the equator; these lines are called meridians. In 1884 the meridian that passes through the Royal Observatory at Greenwich, near London, was chosen as the zero meridian or Prime Meridian. All other meridians radiate eastwards and westwards from it up to 180 degrees. Unlike parallels of latitude, all meridians are of equal length, and they converge at the poles. Together, latitude and longitude form a grid that gives the coordinates of any place.

How Are Longitude and Time Linked?

The Earth makes one complete rotation of 360 degrees in about 24 hours, so it turns 15 degrees in one hour, or 1 degree in 4 minutes. The Earth rotates from west to east, so for every 15 degrees one goes eastwards, local time advances by one hour, and for every 15 degrees westwards it falls behind by one hour. Places east of Greenwich therefore gain time and places west of it lose time. Greenwich Mean Time, sometimes called World Time, is the base for the time zones of the world.

How Do Latitude and Longitude Differ?

Both are used to fix the location of a point, but they measure different things.

The cause of the time difference is the rotation of the Earth.

Why Is This Topic Important?

• Basis of climate zones Latitude controls heat
• Frequent Prelims theme Tropics and Circles
• Map skills Locating places

What Came Next?

The next topic describes the rotation and revolution of the Earth and what each causes, which depends on the lines described here. Next topic: Motions of the Earth: Rotation and Revolution and Their Effects.

Key People and Terms

• Parallel Line of equal latitude
• Equator Zero degree latitude, longest parallel
• Torrid zone Between the Tropics
• Temperate zone Between a Tropic and a Polar Circle
• Frigid zone Beyond a Polar Circle
• Indira Point Southernmost point of India

Exam Corner

Mains Angle

Questions ask why climate differs with latitude. These points add depth.

• Solar energy Direct rays at the equator
• Zones Torrid, temperate and frigid
• India Tropic of Cancer divides the country