🧭 What Will You Learn in This Chapter?
Chapter 1, Locating Places on the Earth, introduces the basic tools used to locate and understand places on our planet. The chapter begins with maps and gradually takes us to the global system of coordinates and time zones.
What is a map and how do we use it? What are its main components?
What are coordinates? How can latitude and longitude be used to mark any location on Earth?
How are local time and standard time related to longitude?
🌎 Introduction: How Do We Find a Place?
Imagine that you visit a city for the first time. You want to find a railway station, school, museum, bank or market. You could ask someone for directions, but another very useful tool is a map.
A map helps us understand where different places are located and how they are connected. It can show a small area such as a neighbourhood or a large area such as a country or even the entire world.
Think of a map as a bird's-eye view of a place. It helps us see locations, distances, directions and important features in a simple form.
🗺️ What Is a Map?
A map is a representation or drawing of an area viewed from above. The area shown on a map may be small, such as a village or town, or very large, such as a state, country or the whole world.
📍 Small Area Maps
These can show places such as a school, neighbourhood, village, town or city.
🌍 Large Area Maps
These can represent states, countries, continents or the entire world.
📚 What Is an Atlas?
An atlas is a book or collection of maps. An atlas may contain maps of countries, states, continents, physical features, political boundaries and many other subjects.
🗺️ Types of Maps
Maps can be created for different purposes. Three important types introduced in this chapter are physical maps, political maps and thematic maps.
| Type of Map | What It Shows | Examples |
|---|---|---|
| Physical Map | Natural features of the Earth | Mountains, oceans, rivers |
| Political Map | Political boundaries and settlements | Countries, states, cities and capitals |
| Thematic Map | A particular theme or subject | Population, rainfall, crops etc. |
📐 Three Important Components of a Map
A map must communicate information clearly. Three important components discussed in this chapter are:
📏 1. Distance
Distance on a map is represented using a scale. Scale helps us understand the actual distance between two places.
🧭 2. Direction
Directions tell us where one place is located in relation to another.
🔣 3. Symbols
Symbols represent real-world features such as roads, railway stations, rivers, schools and other important places.
⭐ Remember
Distance + Direction + Symbols are the three important components of a map.
📏 Scale of a Map
The Earth is huge, so we cannot draw its actual size on a small sheet of paper. A map therefore represents real distances in a reduced form.
Scale shows the relationship between a distance on a map and the corresponding actual distance on the ground.
Example
Suppose a map has a scale of 1 cm = 500 metres. This means that every 1 centimetre measured on the map represents 500 metres on the ground.
🧮 Simple Example
If two places are 4 cm apart on the map and the scale is 1 cm = 500 m:
Actual distance = 4 × 500 m = 2000 m
Therefore, the actual distance is 2 kilometres.
🧭 Directions on a Map
Directions help us describe the position of one place in relation to another.
The Four Cardinal Directions
⬆️ North (N)
Usually shown at the top of a conventional map.
➡️ East (E)
The direction to the right when north is at the top.
⬇️ South (S)
The direction opposite to north.
⬅️ West (W)
The direction opposite to east.
Eight Directions
In addition to the four cardinal directions, maps also use four intermediate directions:
Most maps use an arrow marked N to indicate north.
🔣 Symbols Used on Maps
Imagine trying to draw every building, road, railway line, river and forest exactly as they look in real life. A map would quickly become crowded and difficult to read.
Therefore, maps use symbols to represent different features.
🚆 Transport
Railway lines, railway stations and roads can be represented using conventional symbols.
🌊 Water Features
Rivers, wells, tanks and canals may be shown using specific symbols.
🏛️ Buildings
Schools, post offices, police stations and places of worship can be represented through symbols.
🌳 Natural Features
Trees, grass, forests and other natural features can also be represented using symbols.
The Survey of India, a government organisation, has established conventional symbols used on maps of India and its regions.
🌍 Mapping the Earth
Mapping the Earth is more difficult because the Earth is not a flat surface. It is approximately spherical, although it is slightly flattened at the poles.
A globe represents the Earth's shape more naturally because a globe is also spherical. A flat map, however, is much more convenient for studying and carrying from one place to another.
A globe is a spherical model on which the geography of the Earth can be represented.
📍 Understanding Coordinates
Suppose you need to find a particular square on a chessboard. You can identify it using a combination of a letter and a number.
Similarly, geography uses a system of coordinates to precisely locate places on Earth.
A coordinate system uses two values to identify a specific location.
On Earth, these two coordinates are:
📐 Latitude
Measures how far a place is north or south of the Equator.
📏 Longitude
Measures how far a place is east or west of the Prime Meridian.
🌐 Latitudes
To understand latitude, first identify the North Pole and South Pole.
Halfway between the two poles lies the Equator.
The Equator divides the Earth into the Northern Hemisphere and Southern Hemisphere.
What Are Parallels of Latitude?
Imaginary lines running east-west and parallel to the Equator are called parallels of latitude.
Important Latitude Values
| Location | Latitude |
|---|---|
| Equator | 0° |
| North Pole | 90°N |
| South Pole | 90°S |
🌡️ Latitude and Climate
Latitude is also connected with climate. Regions near the Equator are generally hotter, while areas closer to the poles are colder.
🌐 Longitudes
Lines running from the North Pole to the South Pole are called meridians of longitude. Each meridian is a half-circle.
🏛️ Prime Meridian
To measure longitude, we need a reference meridian. The internationally accepted reference is the Prime Meridian, which is marked as 0° longitude.
It passes through Greenwich in London, England, and is also called the Greenwich Meridian.
East and West Longitudes
Longitudes are measured eastward and westward from the Prime Meridian, from 0° up to 180°.
| Example | Longitude |
|---|---|
| New York | Approximately 74°W |
| Delhi | Approximately 77°E |
| Tokyo | Approximately 140°E |
⚡ Latitude vs Longitude
| Latitude | Longitude |
|---|---|
| Measures distance north or south of the Equator. | Measures distance east or west of the Prime Meridian. |
| Lines run east-west. | Lines run north-south. |
| Parallels are parallel to the Equator. | Meridians meet at the poles. |
| Equator is 0° latitude. | Prime Meridian is 0° longitude. |
📍 Latitude + Longitude = Location
Latitude and longitude together form the two coordinates that can be used to identify a place precisely on Earth.
The intersection of a latitude and longitude gives a precise position.
🧠 Example
A location can be described using a latitude value and a longitude value. For example, Delhi can be described approximately as 29°N latitude and 77°E longitude when using rounded values.
🇮🇳 India's Historical Prime Meridian: Ujjayinī
The chapter also introduces an important aspect of India's history of astronomy.
Many centuries before the Greenwich Meridian became the international reference, Indian astronomers used a reference meridian known as the madhya rekhā, or middle line.
The historical meridian passed through Ujjayinī (present-day Ujjain), which was an important centre of astronomy.
The chapter connects this historical reference with the work of Indian astronomers and the development of astronomical calculations.
⏰ Understanding Time Zones
The Earth rotates on its axis. It completes one full rotation of 360° in about 24 hours.
Therefore, roughly every 15° of longitude corresponds to a difference of about one hour in local time.
🌅 Why Is Time Different in Different Places?
As the Earth rotates from west to east, different parts of the Earth face the Sun at different times. Therefore, it can be morning in one place while it is afternoon, evening or night somewhere else.
🕐 Simple Example
If it is noon at the Prime Meridian, a place approximately 15° east would have a local time about one hour ahead.
A place approximately 30° east would be about two hours ahead.
🕰️ Local Time vs Standard Time
Since local time changes with longitude, a large country could have many different local times. This would be inconvenient for administration, transport and communication.
Therefore, countries generally adopt a standard time for practical use.
| Local Time | Standard Time |
|---|---|
| Based on the longitude of a particular place. | A common official time adopted by a country or region. |
| Can vary from one place to another. | Helps maintain a common time. |
| Closely connected with the position of the Sun. | Used for practical and administrative purposes. |
🇮🇳 Indian Standard Time (IST)
India uses a common standard time called Indian Standard Time (IST).
IST is commonly expressed as GMT/UTC + 5:30.
🌄 Why Can Sunrise Differ Across India?
India extends across a considerable range of longitudes. Therefore, the local time of places in the west and east can differ even though the whole country follows the same standard time.
For example, a place in Assam can experience sunset earlier according to local solar time than a place in Gujarat, even though both places follow IST.
🌐 World Time Zones
Countries across the world use standard times organised broadly into time zones.
The boundaries of time zones do not always follow straight meridians. They often adjust to country boundaries and practical requirements.
Not every country has only one time zone. Very large countries may have several time zones.
📅 International Date Line
The International Date Line is located approximately along 180° longitude, opposite the Prime Meridian.
It is associated with the change of calendar date. When the International Date Line is crossed, the date changes by one day.
✈️ Travelling Eastward
Crossing the International Date Line eastward means subtracting one day from the date.
✈️ Travelling Westward
Crossing it westward means adding one day to the date.
The International Date Line is approximately at 180° longitude, but it bends in places to avoid unnecessarily dividing countries into different calendar dates.
⚡ Chapter 1 Quick Revision
- A map represents an area as viewed from above.
- An atlas is a collection of maps.
- The three important map components are distance, direction and symbols.
- Scale represents the relationship between map distance and actual ground distance.
- The four cardinal directions are North, East, South and West.
- The intermediate directions are NE, SE, SW and NW.
- The Equator is 0° latitude.
- The North Pole is 90°N and the South Pole is 90°S.
- The Prime Meridian is 0° longitude.
- Latitude measures distance north or south of the Equator.
- Longitude measures distance east or west of the Prime Meridian.
- Latitude and longitude together provide coordinates for locating places.
- Earth rotates 360° in approximately 24 hours, giving about 15° of rotation per hour.
- India follows Indian Standard Time (IST), which is 5 hours 30 minutes ahead of Greenwich.
- The International Date Line lies approximately along 180° longitude.
🎯 Important Questions for Revision
1. What is a map?
A map is a representation or drawing of an area viewed from above.
2. What are the three main components of a map?
Distance, direction and symbols.
3. What is scale?
Scale shows the relationship between distance on a map and the corresponding actual distance on the ground.
4. What are cardinal directions?
North, East, South and West are the four cardinal directions.
5. What is latitude?
Latitude measures the distance of a place north or south of the Equator.
6. What is longitude?
Longitude measures the distance of a place east or west of the Prime Meridian.
7. What is the Prime Meridian?
The Prime Meridian is the 0° longitude passing through Greenwich in London.
8. Why do countries use standard time?
Because different places have different local times, a common standard time makes communication, administration and everyday activities more convenient.
9. What is Indian Standard Time?
Indian Standard Time is India's standard time and is 5 hours 30 minutes ahead of Greenwich.
10. What is the International Date Line?
It is an approximately 180° longitude line associated with a change of one calendar day when crossed.