Latitude, Longitude, and Time Zones
Delhi Police & SSC Exams Preparation
1. Introduction
To locate any place on Earth accurately, geographers use an imaginary grid made up of latitude and longitude lines. These help in determining exact location, time zones, and distance between places.
Key Concepts:
- Latitude: Horizontal lines measuring distance from Equator
- Longitude: Vertical lines measuring distance from Prime Meridian
- Time Zones: Based on longitudinal divisions
- Grid System: Intersection of latitude and longitude
Significance:
Fundamental for navigation, time calculation, and geographical positioning
Exam Trick: "Lati is Flat, Long is Tall" → Latitude = Horizontal, Longitude = Vertical
2. Latitudes
Key Facts:
- Definition: Imaginary horizontal lines parallel to Equator
- Equator: 0° latitude, divides Earth into Northern & Southern Hemispheres
- Poles: 90°N (North Pole) and 90°S (South Pole)
- Total: 90 latitudes in each hemisphere (180 total excluding Equator)
Importance:
Determines climate zones and seasonal variations
Exam Trick: "E-T-T-A-A-N-S" → Equator, Tropic of Cancer, Tropic of Capricorn, Arctic, Antarctic, North, South
3. Important Parallels of Latitude
| Latitude | Name | Significance |
|---|---|---|
| 0° | Equator | Divides Earth into two equal halves |
| 23½° N | Tropic of Cancer | Northern limit of Sun's vertical rays |
| 23½° S | Tropic of Capricorn | Southern limit of Sun's vertical rays |
| 66½° N | Arctic Circle | Northern polar boundary |
| 66½° S | Antarctic Circle | Southern polar boundary |
| 90° N/S | North/South Pole | Extreme north/south points |
4. Longitudes
Key Facts:
- Definition: Imaginary vertical lines from North to South Pole
- Prime Meridian: 0° longitude through Greenwich, London
- Total: 360 longitudes (180° East & 180° West)
- Meeting Point: All longitudes meet at poles
Importance:
Determines time zones and helps in navigation
Exam Trick: "Long lines meet at poles"
5. Grid System
How It Works:
- Intersection: Latitude and longitude lines form grid
- Coordinates: Used to determine exact position
- Example: Delhi's location: 28.6° N latitude, 77.2° E longitude
- Accuracy: Provides precise geographical positioning
Applications:
Essential for GPS, navigation systems, and mapping
6. Longitude and Time Relationship
Key Principles:
- Earth Rotation: 360° in 24 hours = 15° per hour
- Time Difference: 15° longitude = 1-hour time difference
- Rotation Direction: West to east
- Time Calculation: Time increases eastward, decreases westward
Formula:
Time difference (minutes) = Longitude difference × 4
Exam Trick: "4 minutes for 1° move, East = Add, West = Remove"
7. Standard Time and Time Zones
Key Concepts:
- Standard Time: Uniform time within a country/region
- Indian Standard Time (IST): Based on 82½° E longitude
- IST Difference: 5 hours 30 minutes ahead of GMT
- Global Time Zones: 24 time zones worldwide
Purpose:
Avoids confusion and maintains uniform time within regions
8. Important Standard Times
| Country/Time Zone | Standard Meridian | Time Difference from GMT |
|---|---|---|
| India (IST) | 82°30′ E | +5:30 hours |
| UK (GMT) | 0° | 0 hours |
| Japan (JST) | 135° E | +9 hours |
| USA (EST) | 75° W | -5 hours |
| Australia (AEST) | 150° E | +10 hours |
Exam Trick: "East is plus, West is minus — Time flies eastward"
9. International Date Line (IDL)
Key Facts:
- Location: 180° longitude, opposite Prime Meridian
- Function: Separates two consecutive calendar days
- West to East: Subtract one day when crossing
- East to West: Add one day when crossing
Significance:
Maintains consistent date calculation globally
Exam Trick: "180° — where today meets tomorrow"
10. Quick Comparison – Latitude vs Longitude
| Feature | Latitude | Longitude |
|---|---|---|
| Direction | East–West | North–South |
| Parallel Lines | Yes | No |
| Max Value | 90° | 180° |
| Determines | Climate | Time |
| Example | Equator, Tropic of Cancer | Prime Meridian, IDL |
Exam Trick: "Flat → Climate, Tall → Time"
PYQs (Delhi Police + SSC + State Exams)
The latitude which divides the Earth into two equal halves is —
Options: (a) Tropic of Cancer (b) Equator (c) Tropic of Capricorn (d) Prime Meridian
Category: Basic Concepts
Show Answer
Equator
The Prime Meridian passes through —
Options: (a) Paris (b) New York (c) Greenwich (d) Tokyo
Category: Longitudes
Show Answer
Greenwich
The Earth's rotation of 1° corresponds to a time difference of —
Options: (a) 2 minutes (b) 4 minutes (c) 6 minutes (d) 8 minutes
Category: Time Calculation
Show Answer
4 minutes
Indian Standard Time (IST) is ahead of Greenwich Mean Time (GMT) by —
Options: (a) 4 hours 30 minutes (b) 5 hours 30 minutes (c) 6 hours (d) 6 hours 30 minutes
Category: Time Zones
Show Answer
5 hours 30 minutes
The Standard Meridian of India passes through —
Options: (a) 82°30′ E (b) 90° E (c) 75° E (d) 66°30′ E
Category: Indian Geography
Show Answer
82°30′ E
How many time zones are there in the world?
Options: (a) 12 (b) 24 (c) 36 (d) 48
Category: Global Time
Show Answer
24
The line opposite to the Prime Meridian is —
Options: (a) Arctic Circle (b) Equator (c) International Date Line (d) Tropic of Capricorn
Category: Longitudes
Show Answer
International Date Line
If it is 12 noon at Greenwich, what will be the time at 82°30′ E (India)?
Options: (a) 4:30 AM (b) 5:30 AM (c) 5:30 PM (d) 10:30 PM
Category: Time Calculation
Show Answer
5:30 PM
The Tropic of Cancer passes through which of the following states of India?
Options: (a) Rajasthan (b) Tripura (c) Gujarat (d) All of these
Category: Indian Geography
Show Answer
All of these
The longitude which determines Indian Standard Time is —
Options: (a) 80° E (b) 82°30′ E (c) 90° E (d) 75° E
Category: Time Zones
Show Answer
82°30′ E
Final Exam Tip
Focus on angles, direction, and IST-GMT difference. Remember 4 minutes per degree and 15° = 1 hour rule. 82½° E = IST is one of the most repeated PYQs in Delhi Police exams. Practice map-based MCQs — at least one question is guaranteed from this topic!
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