1. Chapter at a Glance
How do you tell a friend where to meet you in a crowded market? You give clear directions — “the 7th shop in the 5th row”. Geographers do the same for the whole Earth. This chapter explains what a map is and its three main parts, why a globe is the truest model of the Earth, how latitudes and longitudes help us fix the exact position of any place, and how longitude is linked to local time, standard time and time zones.
- Maps, atlases and types of maps — physical, political and thematic.
- Three components of a map: distance (scale), direction and symbols.
- The globe; parallels of latitude; meridians of longitude; coordinates.
- The Prime Meridian at Greenwich and India's ancient prime meridian at Ujjain.
- Local time, Indian Standard Time, time zones and the International Date Line.
2. What Is a Map?
A map is a drawing of an area of the Earth's surface as seen from above. It can show a small area, like a school or village, or a very large one, like India or the whole world. A book or collection of maps is called an atlas.
| Type of map | What it shows | Example |
|---|---|---|
| Physical map | Natural features such as mountains, plains, rivers and oceans | Physical map of India showing the Himalayas and the Ganga |
| Political map | Countries, states, boundaries, cities and capitals | Map of India with States, Union Territories and capitals |
| Thematic map | One special kind of information | Maps of rainfall, crops, forests or population |
3. Components of a Map
(a) Distance and scale
A whole city cannot fit on paper at its real size, so maps are drawn to a scale. The scale tells us how much real distance one unit on the map stands for — for example, 1 cm = 500 m. If two places are 3 cm apart on such a map, they are 3 × 500 = 1,500 m (1.5 km) apart on the ground.
(b) Direction
The four cardinal directions are North, East, South and West (going clockwise from the top). Between them lie the intermediate directions — North-East (NE), South-East (SE), South-West (SW) and North-West (NW). Most maps show an arrow marked “N” pointing to the north.
(c) Symbols
There is no space to draw every building, road or tree on a map, so map-makers use symbols — small signs, lines and colours. In India, the Survey of India, a government body, has fixed standard symbols for railway lines, roads, boundaries, rivers, wells, places of worship, post offices, police stations and more. Common colours: blue for water, green for plains or forests, brown for mountains and highlands.
4. The Globe and Coordinates
The Earth is almost a sphere — slightly flattened at the poles. A flat map cannot show a round surface without some stretching (try flattening an orange peel and it tears). A globe is a small model of the Earth with the same round shape, so it shows shapes, sizes and directions more correctly than a flat map.
To fix the position of a place we use two numbers called coordinates, just as a chess move like “d4” uses a letter for the column and a number for the row. On the Earth, the two coordinates are latitude and longitude.
Latitudes (parallels)
- The Equator is an imaginary circle midway between the North and South Poles. It is 0° latitude and the longest parallel.
- Latitude measures how far a place is north or south of the Equator, in degrees, up to 90°N (North Pole) and 90°S (South Pole).
- Parallels of latitude are circles that become smaller towards the poles.
- Climate changes with latitude: hot (torrid) near the Equator, moderate (temperate) in middle latitudes, cold (frigid) near the poles.
Longitudes (meridians)
- Meridians are half-circles running from the North Pole to the South Pole. All meridians are of equal length.
- In 1884, several nations agreed to take the meridian passing through Greenwich (in London) as the Prime Meridian, 0° longitude.
- Longitude is counted from 0° to 180° east (E) or west (W). The 180°E and 180°W lines are the same line, written simply as 180°.
- Rounded examples: New York about 74°W; Delhi about 77°E; Tokyo about 140°E.
The network of latitudes and longitudes on a globe forms a grid. The Equator divides the Earth into the Northern and Southern Hemispheres; the Prime Meridian (with the 180° line) divides it into the Eastern and Western Hemispheres. Mainland India lies roughly between 8°N and 37°N latitude and 68°E and 97°E longitude, so India is in the Northern and Eastern Hemispheres.
Long before Greenwich, Indian astronomers used a prime meridian called the madhya rekhā (“middle line”). It passed through Ujjayinī (Ujjain), a famous centre of astronomy where the astronomer Varāhamihira worked about 1,500 years ago. Indian astronomical texts used this meridian as the reference for their calculations.
5. Longitude and Time
The Earth spins from west to east and makes one full turn (360°) in 24 hours. So it turns 15° in one hour (360 ÷ 24 = 15), or 1° in 4 minutes. When the Sun is overhead at one meridian, it is noon there — this is its local time. Places to the east see the Sun earlier, so their local time is ahead; places to the west are behind. If it is 12 noon at Greenwich, it is 1 pm at 15°E and 11 am at 15°W.
If every town used its own local time, trains and offices would be very confusing. So a country chooses one meridian and uses its time everywhere — this is its standard time. Indian Standard Time (IST) is based on the 82.5°E meridian and is 5 hours 30 minutes ahead of Greenwich Mean Time (GMT): 82.5 × 4 min = 330 min = 5 h 30 min. That is why when it is noon in London, it is 5:30 pm in India.
Time zones and the International Date Line
The world is divided into time zones, which roughly follow 15° belts but bend along country borders. Very large countries have several time zones — the USA has six and Russia has eleven. The line roughly along 180° longitude is the International Date Line. Crossing it eastward, you subtract a day; crossing it westward, you add a day. It zig-zags in places so that no country is split into two dates.
Porbandar (Gujarat) and Tinsukia (Assam) differ by about 30° of longitude. Local time difference = 30 × 4 min = 120 min = 2 hours. That is why the Sun may already have set in Tinsukia while Porbandar still has daylight — yet both follow the same IST.
6. Master Table: Key Terms
| Term | Meaning |
|---|---|
| Map / Atlas | Drawing of an area seen from above / book of maps |
| Scale | Map distance : real distance, e.g. 1 cm = 500 m |
| Cardinal directions | N, E, S, W; intermediate: NE, SE, SW, NW |
| Latitude | Distance N or S of the Equator (0° to 90°) |
| Longitude | Distance E or W of the Prime Meridian (0° to 180°) |
| Time and longitude | 15° = 1 hour; 1° = 4 minutes |
| IST | Based on 82.5°E; GMT + 5 h 30 min |
| International Date Line | About 180°; date changes by one day |
7. Master Summary Table
| Feature | Latitudes (parallels) | Longitudes (meridians) |
|---|---|---|
| Direction | Run east–west | Run north–south, pole to pole |
| Shape | Full circles | Half-circles |
| Length | Decrease towards the poles | All equal |
| Zero line | Equator (0°) | Prime Meridian at Greenwich (0°) |
| Range | 0° to 90°N / 90°S | 0° to 180°E / 180°W |
| Main use | Location and climate zones | Location and time |
Chart — standard time of some countries ahead of GMT (hours):
8. Mind Map
- Physical, political, thematic
- Distance, direction, symbols
- True model of Earth
- Grid of lines
- Equator 0°
- Poles 90°
- Greenwich 0°
- Ujjain madhya rekhā
- 15° = 1 hour
- IST, time zones, IDL
9. Tips and Tricks
- “Never Eat Soggy Waffles” — North, East, South, West, clockwise.
- Latitude = ladder rungs (flat, side to side); longitude = long lines from pole to pole.
- Going East, time increases (“East = Early sunrise”).
- Time difference = difference in longitude × 4 minutes.
- Saying all latitudes are equal in length — only meridians are equal.
- Thinking IST is the same as local time everywhere in India.
- Forgetting to write N/S or E/W with degrees.
10. Important One-liners
- An atlas is a collection of maps.
- The three components of a map are distance, direction and symbols.
- The Survey of India fixes standard map symbols for India.
- The Equator is the longest parallel of latitude.
- All meridians of longitude are equal in length.
- The Prime Meridian passes through Greenwich (fixed in 1884).
- Ujjain was the prime meridian of ancient Indian astronomy.
- The Earth rotates 15° in one hour.
- IST is 5 hours 30 minutes ahead of GMT.
- The International Date Line lies roughly along 180°.
11. Exam-pattern Questions with Detailed Answers
Which line is 0° latitude?
- Prime Meridian
- Equator
- Tropic of Cancer
- International Date Line
Show answer
The Equator lies midway between the poles and is 0° latitude.
Answer: (B) Equator
Name the three components of a map.
Show answer
Distance (shown by scale), direction, and symbols.
Answer: Distance, direction, symbols
What colour is usually used on maps to show water bodies?
Show answer
Blue is used for oceans, seas, lakes and rivers.
Answer: Blue
On a map with scale 1 cm = 10 m, a playground measures 4 cm × 3 cm. What are its real length and width?
Show answer
Length = 4 × 10 = 40 m; width = 3 × 10 = 30 m.
Answer: 40 m by 30 m
Why is it 5:30 pm in India when it is 12 noon in London?
Show answer
IST is based on 82.5°E. Each degree equals 4 minutes, so 82.5 × 4 = 330 minutes = 5 h 30 min. India is east of Greenwich, so its time is ahead: noon + 5:30 = 5:30 pm.
Answer: India's standard meridian (82.5°E) gives IST = GMT + 5 h 30 min
Differentiate between local time and standard time.
Show answer
Local time depends on the position of the Sun at a place's own meridian, so it differs from place to place. Standard time is one common time, based on a chosen central meridian, used throughout a country or zone for convenience.
Answer: Local time varies with longitude; standard time is one common time for a region
Delhi and Bengaluru both lie near 77°E longitude, but at latitudes about 29°N and 13°N. What is the difference in their local time?
Show answer
Local time depends on longitude, not latitude. Same longitude means no difference in local time.
Answer: No difference (zero)
True or false? Give a reason. (a) All parallels have the same length. (b) In Assam, local time and IST are identical. (c) The length of a meridian is half that of the Equator.
Show answer
(a) False — parallels become smaller towards the poles. (b) False — Assam lies east of 82.5°E, so its local time is ahead of IST. (c) True — a meridian is a half-circle from pole to pole, while the Equator is a full circle around the Earth.
Answer: False, False, True
If it is 10 am at Greenwich, what is the local time at (a) 45°E (b) 30°W?
Show answer
(a) 45° ÷ 15 = 3 hours ahead (east): 1 pm. (b) 30° ÷ 15 = 2 hours behind (west): 8 am.
Answer: (a) 1 pm (b) 8 am
Why is a globe a better model of the Earth than a flat map? Why do we still use maps?
Show answer
The globe has the same round shape as the Earth, so shapes, sizes and directions are shown correctly. A flat map must stretch some parts. But a globe is bulky, shows only half the Earth at a time and cannot show small areas in detail; maps are easy to carry, can show the whole world at once or a small village in great detail.
Answer: Globe is accurate; maps are handy and detailed
A ship crosses the International Date Line travelling westward on a Sunday. What day will it be after crossing? Why does the line zig-zag?
Show answer
Travelling westward across the line, a day is added: Sunday becomes Monday. The line bends around some island countries so that a single country does not have two different dates at the same time.
Answer: Monday; to keep each country on one date
12. Quick Revision Summary
- Maps: physical, political, thematic; components — scale, direction, symbols.
- A globe is the truest model of the Earth.
- Latitude: N/S of the Equator, 0°–90°; longitude: E/W of Greenwich, 0°–180°.
- Ancient India's prime meridian passed through Ujjain.
- 15° = 1 hour; IST (82.5°E) = GMT + 5:30; time zones; International Date Line at about 180°.