Chapter 1 Locating Places On The Earth

A Map And Its Components

A map serves as a visual depiction, or a drawing, of a specific geographic area. This area can vary greatly in size, from a small village or town to an entire district, state, country, or even the entire planet. Maps essentially provide a bird's-eye view of the Earth's surface or a portion of it.

A collection of maps is typically bound together in a book called an atlas.

Maps can be categorized based on the type of information they present:

• Physical Maps: These primarily show natural geographical features such as mountains, oceans, and rivers.
• Political Maps: These illustrate political divisions like countries, states, boundaries, and cities.
• Thematic Maps: These focus on displaying a specific type of information, such as population distribution, rainfall patterns, or forest areas.

To effectively interpret and use maps, three key components are essential: distance, direction, and symbols.

Distance

Representing vast areas on a small piece of paper is possible through the concept of scale. The scale of a map indicates the relationship between the distance measured on the map and the actual distance on the ground.

For example, a scale of "1 cm = 500 m" means that every centimetre measured on the map corresponds to 500 metres in reality. Scales can also be shown graphically using a ruler-like bar.

Understanding the map's scale is crucial for calculating real-world distances between locations depicted on the map.

Answer:

Direction

Maps help us determine directions. The four main directions are North, East, South, and West. These are known as the cardinal directions or cardinal points.

Often, maps include an arrow labelled 'N' pointing towards North. Once North is known, the other cardinal directions can be easily identified: East is to the right of North, South is opposite North, and West is opposite East.

In addition to the cardinal directions, intermediate directions are also used: Northeast (NE), Southeast (SE), Southwest (SW), and Northwest (NW). These lie exactly between the cardinal points.

Symbols

Maps use symbols to represent various features on the ground. Since there isn't enough space on a map to draw every building, road, river, or landmark in detail, standardized symbols are used instead.

These symbols allow a large amount of information to be shown within the limited space of a map. Different symbols represent different things, like railway stations, schools, roads, rivers, forests, etc.

To ensure maps are easily understood globally, mapmakers often use standard or conventional symbols. Different countries may have their own sets of symbols. In India, the Survey of India has established a standard set of symbols for maps.

Mapping The Earth

Creating an accurate map of the entire Earth on a flat surface like paper is challenging because the Earth is approximately spherical, not flat. Attempting to flatten a spherical surface inevitably leads to distortion (imagine trying to flatten an orange peel without tearing it).

A globe is a spherical model of the Earth (or other celestial body). Because it shares the same shape as the Earth, a globe provides a more accurate representation of the Earth's geography compared to a flat map.

Understanding Coordinates

To pinpoint the exact location of any place on the Earth, a system of coordinates is used. This system works by using two reference points or lines to define a unique position.

Think of locating a shop in a market by its row and shop number (e.g., 5th row, 7th shop) or identifying a square on a chessboard using a letter and a number (e.g., d4). In both cases, two pieces of information (coordinates) are used to find a specific spot.

Similarly, on the Earth's surface, a system of imaginary lines creates a grid that allows us to define the precise location of any point using two coordinates.

Latitudes

Imaginary lines drawn on the Earth's surface, running from east to west and parallel to the Equator, are called parallels of latitude. These lines form circles around the Earth.

The largest parallel of latitude is the Equator, which is located exactly halfway between the North Pole and the South Pole. As you move towards either pole, the parallels of latitude become smaller circles.

Latitude is a measure of the angular distance of a point north or south of the Equator. It is expressed in degrees.

• The Equator is designated as 0° latitude.
• The North Pole is at 90° North (90°N) latitude.
• The South Pole is at 90° South (90°S) latitude.

Latitude is closely related to climate. Regions near the Equator (low latitudes) tend to have a hot, or torrid, climate. As latitude increases (moving away from the Equator towards the poles), the climate generally becomes more moderate, or temperate. Regions close to the poles (high latitudes) experience cold, or frigid, climates.

Longitudes

Imaginary lines running from the North Pole to the South Pole are called meridians of longitude. These lines are not parallel like latitudes; they are all half-circles that converge at the poles.

Unlike latitudes, there is no natural starting point for measuring longitude. By international agreement in 1884, the meridian passing through Greenwich, near London, was chosen as the reference line. This is called the Prime Meridian and is designated as 0° longitude.

Longitude is a measure of the angular distance of a point east or west of the Prime Meridian. It is also measured in degrees, ranging from 0° to 180° east (E) or west (W). The meridian at 180° is the same whether approached from the east or the west.

Longitude is directly related to the Earth's rotation and, consequently, to time. As the Earth rotates from west to east, different longitudes face the sun at different times, leading to variations in local time.

Together, latitude and longitude form a grid on the Earth's surface. These two coordinates uniquely identify the location of any point on the planet.

The grid formed by the parallels of latitude and meridians of longitude is sometimes referred to as grid lines.

Interesting Fact: Ancient Indian astronomers were aware of latitude and longitude concepts and had their own reference meridian, called the madhya rekhā or 'middle line'. This meridian passed through the city of Ujjayinī (modern Ujjain), which was a significant centre for astronomy.

Understanding Time Zones

The Earth completes one full rotation ($360^\circ$) on its axis in approximately 24 hours. This rotation causes the difference in time between places located at different longitudes.

Since $360^\circ$ of longitude corresponds to 24 hours, a rotation of $15^\circ$ of longitude corresponds to 1 hour ($360^\circ / 24 \text{ hours} = 15^\circ / \text{hour}$).

Moving eastward from a reference point, time increases by 1 hour for every $15^\circ$ of longitude. Moving westward, time decreases by 1 hour for every $15^\circ$ of longitude.

The time at any given longitude is called its local time, which is determined by the position of the sun in the sky at that specific location.

Standard Time

Using the local time for every town or village in a country would be very inconvenient, especially for activities like train travel or communication. To avoid this, most countries adopt a standard time. This is usually the local time of a central meridian of longitude passing through the country.

For India, the standard time is based on the meridian approximately at $82.5^\circ$ East longitude. Indian Standard Time (IST) is 5 hours and 30 minutes (5.5 hours) ahead of Greenwich Mean Time (GMT), which is the local time at the Prime Meridian (0° longitude).

Time Zones

The world is divided into areas called time zones, where all locations within a zone share the same standard time. These zones roughly follow the 15° longitude lines ($360^\circ / 24 = 15^\circ$), but their boundaries are often adjusted to align with international borders and political divisions for convenience.

The standard time within a zone is typically expressed as a difference (in hours and sometimes half-hours) from GMT or UTC (Coordinated Universal Time, which is essentially the modern equivalent of GMT).

Large countries, such as Russia, Canada, and the USA, span across multiple longitudes and therefore have multiple time zones to reflect the significant differences in local time from east to west.

International Date Line

Located approximately at the 180° longitude meridian, opposite the Prime Meridian, is the International Date Line (IDL). This imaginary line marks the place where the calendar date changes.

When you cross the International Date Line, you either add or subtract a day:

• Travelling eastward across the IDL, you subtract a day (e.g., Saturday becomes Friday).
• Travelling westward across the IDL, you add a day (e.g., Saturday becomes Sunday).

The International Date Line does not follow the 180° meridian perfectly straight. It zigs and zags in places to avoid dividing countries or island groups into two different calendar days.