Locating Places on Earth
Read top to bottom — it follows the order of the chapter. Tick each section off as you finish it.
1 · Maps
Map = a drawing of an area, looked at from the top. Atlas = a collection of maps.
Three kinds
| Type | Shows |
|---|---|
| Physical | Natural features — mountains, oceans, rivers |
| Political | Countries, states, boundaries, cities, capitals |
| Thematic | One specific kind of information |
Three components — remember D–D–S
| Component | The tool | Key fact |
|---|---|---|
| Distance | Scale | 1 cm on map = a fixed real distance. On the India map, 2.5 cm = 500 km |
| Direction | Cardinal points | N at top, then clockwise E, S, W. In-between: NE, SE, SW, NW. Arrow marked ‘N’ |
| Symbols | Standard symbol set | Fixed for India by the Survey of India. Saves space on crowded maps |
2 · Why we need a globe
- The Earth is nearly a sphere — slightly flattened at the poles.
- A sphere cannot be shown accurately on flat paper.
- Orange-peel test: peel into 3–4 big pieces, try to flatten → it tears at the edges.
- Globe = a sphere with a map drawn on it. Same shape as the Earth, so it represents geography better than a flat map.
3 · Coordinates — the big idea
Two values together fix one position.
| Example | The two values |
|---|---|
| Market | 7th shop, 5th row |
| Chessboard | letter a–h + number 1–8 → pawn moves d2 to d4 |
| The Earth | latitude + longitude |
4 · Latitude vs Longitude
| LATITUDE | LONGITUDE | |
|---|---|---|
| Measures distance from | the Equator | the Prime Meridian |
| Lines called | parallels of latitude | meridians of longitude |
| Direction of lines | run east–west | run north–south (pole to pole) |
| Shape | full circles | half-circles |
| Length | unequal — Equator longest, shrink towards poles | all equal |
| Range | 0° → 90°N and 90°S | 0° → 180° E and W |
| Zero line | Equator = 0° | Prime Meridian = 0° |
| Divides Earth into | Northern / Southern hemispheres | Western / Eastern hemispheres |
| Controls | Climate | Time |
Round-figure longitudes: New York 74°W · Delhi 77°E · Tokyo 140°E
Delhi’s coordinates: about 29°N, 77°E
Prime Meridian — also called the Greenwich Meridian. Fixed by international agreement in 1884; Greenwich is an area of London, England.
Grid = all parallels + all meridians together (also ‘grid lines’).
5 · Latitude and climate
| Latitude | Climate | Name |
|---|---|---|
| Near the Equator | Hot | torrid |
| Middle latitudes | Moderate | temperate |
| Near the poles | Cold | frigid |
6 · India’s own prime meridian
- Greenwich was not the first prime meridian.
- India’s was the madhya rekhā — ‘middle line’.
- It passed through Ujjayinī, today Ujjain — a great centre of astronomy, at about 75.8°E.
- Varāhamihira, a famous astronomer, lived and worked there about 1,500 years ago.
- Indian astronomers already understood latitude, longitude and the need for a zero meridian. The Ujjayinī meridian was the reference in all Indian astronomical texts.
- Ancient cities on it: Kurukṣhetra, Rohitaka/Rohtak, Mālavangara/Nagar, Ujjayinī/Ujjain, Māhiṣhmati/Maheshwar, Kumārī/Kanyakumari.
7 · Longitude and time
The Earth spins WEST to EAST · one full turn = 24 hours · one turn = 360°
→ 360 ÷ 24 = 15° PER HOUR (and 1° = 4 minutes)
Rule: go EAST → time is AHEAD (add). Go WEST → time is BEHIND (subtract).
Starting from 12 noon at Greenwich:
| 45°W | 30°W | 15°W | 0° | 15°E | 30°E | 45°E |
|---|---|---|---|---|---|---|
| 9 AM | 10 AM | 11 AM | 12 PM | 1 PM | 2 PM | 3 PM |
8 · Local time vs standard time
| Local time | Standard time | |
|---|---|---|
| Based on | the place’s own meridian | one meridian chosen for the whole country |
| Varies | with every meridian | same across the country |
| The point | a country would need dozens of clocks | one convenient clock for all |
→ That is why it is 5:30 pm in India when it is 12 noon in London.
Time zones broadly follow the 15° bands, but the dividing lines are not straight — they bend to follow international borders so a country isn’t split.
On a time-zone map the number inside a country = hours to add to GMT (+) or subtract from GMT (−).
Not one zone per country: USA = 6 zones · Russia = 11 zones (reset your watch 10 times crossing Russia). Half-hour offsets exist too: India +5.5, others +3.5, +4.5, +6.5, +9.5.
9 · International Date Line
- Sits opposite the Prime Meridian, at approximately 180° longitude.
- The +12 and −12 time zones touch along it.
| Direction of travel | Date change |
|---|---|
| Eastward | Subtract a day (Monday → Sunday) |
| Westward | Add a day (Sunday → Monday) |
Only approximately at 180° — it deviates to avoid splitting a country into two different dates.
10 · Ten facts most likely to be asked
- Three components of a map = distance, direction, symbols
- Survey of India fixes India’s map symbols
- Earth is flattened at the poles
- Equator = 0°; poles = 90°N / 90°S
- Parallels are unequal, meridians are all equal in length
- Prime Meridian fixed at Greenwich in 1884, = 0° longitude
- madhya rekhā through Ujjayinī; Varāhamihira, ~1,500 years ago
- Earth turns 15° per hour
- IST = GMT + 5:30
- IDL near 180°; east → subtract a day, west → add a day
Common mistakes to avoid
- Saying latitude is 0° at the poles — it is 0° at the Equator
- Calling NE/SW “cardinal” — they are intermediate directions
- Thinking latitude affects the time — only longitude does
- Writing 180°E and 180°W as different meridians — they are the same
- Saying time-zone lines are exactly the meridians — they bend along borders
- Reversing the Date Line rule — east = subtract, west = add