Locating Places on the Earth

A map is like a treasure guide. It shows you where things are and how to get to them.

What is a Map?

A map is a representation, or a drawing, of some area. It may be a small area (village or town), a bigger area (district or state), or a very large area like India or even the whole world.

An atlas is a book or collection of maps.

Types of Maps

Physical maps show some natural features such as mountains, oceans and rivers.

Political maps show details of countries or states, boundaries, and cities. For example, a map of India with all its States, Union Territories and their capitals.

Thematic maps show specific kind of information.

Components of Map

There are three important components of maps - distance, direction and symbols.

1. Distance

The actual distance between two points represented on the map depends on the scale that the map is using. For example, if each centimetre on the map represents 500 metres on the ground, we say that the scale is 1 cm = 500 m.

2. Direction

Four directions are are north, at the top, and, moving clockwise, east, south and west. These are called the cardinal directions or cardinal points.

Other than these, intermediate directions are also used - northeast (NE), southeast (SE), southwest (SW) and northwest (NW). Most maps simply have an arrow marked with the letter "N", which points to the north direction.

3. Symbols

A symbol is used to represent features on the map - for different kinds of buildings (a railway station, a school, a post office), for roads and railway lines, and for natural elements such as a river, a pond or a forest. In that way, numerous details can be shown in the limited space available on a map.

Mapping the Earth

Mapping the Earth is a little more difficult because our planet is not a flat surface. It nearly has the shape of a sphere. Representing a sphere accurately on a flat sheet of paper is not possible.

A globe is a sphere on which a map is drawn.

A system of coordinates is used in the world of maps to determine the location of any place on a map. Latitude and longitude together are the two coordinates of a place. With them, you can locate any place on the Earth.

Latitudes

In a globe, the fixed points at the top and bottom are the two poles. Halfway between them is the Equator.

Latitude measures the distance from the Equator. At any point, you can draw an imaginary line that runs east and west, parallel to the Equator. Such a line is called a parallel of latitude and it draws a circle around the Earth. The largest circle is the Equator, while the circles marked by the parallels of latitude grow smaller as we move northward or southward.

Latitudes are expressed in degrees. By convention, the Equator is latitude 0° (zero degree), while the latitudes of the two poles are 90°N (North) and 90°S (South) respectively.

Connection Between Latitude and Climate

Around the Equator, the climate is generally hot (torrid). As you travel away from the Equator towards one of the two poles, the climate becomes more moderate (temperate). Closer to the North or South Pole, the climate grows colder (frigid).

Longitudes

Longitudes are all half-circles running from one pole to the other.

To measure longitudes, we define a reference point called the Prime Meridian. It is also called Greenwich Meridian because, in the year 1884, some nations decided that the meridian passing through Greenwich, an area of London in England, would become the international standard for the Prime Meridian. It is marked as 0° longitude.

Just as latitude is a measure of the distance from the Equator if you travel towards one of the poles, longitude is a measure of the distance from the Prime Meridian if you travel along the Equator. Longitude is also measured in degrees. Westward or eastward, it increases in value from 0° to 180°, with the letter ‘W’ or ‘E’ added. For example, New York’s longitude is 74°W, while Delhi’s is 77°E and Tokyo’s is 140°E.

Time Zones

The earth spins around its axis, making a full turn every 24 hours. A full turn is 360°, which means 15° per hour (15 × 24 = 360). If it is 12 pm or noon at Greenwich, it is 1 pm local time at 15°E, 2 pm at 30°E, and so on. Going westward, it is the other way round - 11 am local time at 15°W, 10 am at 30°W and so on.

The same method can be used to calculate the local time of any place on the Earth. But it would not be convenient for a country to use many local times. That is why most countries adopt a standard time based on a meridian passing through them. Indian Standard Time (IST) is 5 hours 30 minutes ahead of the local time at Greenwich (called Greenwich Mean Time or GMT).

While the Prime Meridian was fixed at Greenwich, the opposite line at approximately 180° longitude is called the International Date Line.