NDA Geography · World and Human Geography

World Coordinates, Time and Place

How latitude and longitude fix a place on the globe, how longitude controls local time (GMT offsets, the Prime Meridian) and what happens when you cross the International Date Line.

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Why this matters

4 PYQs, all MODERATE. Two are pure recall (which capital is northernmost, which African country the Prime Meridian misses), but two test a RULE: time changes with longitude (1 hour per 15°), so the country farthest east of Greenwich has the biggest time difference, and crossing the International Date Line east means you set the clock back a day. Learn the rule and you don't have to memorise every case.

Concept 1 of 3

Latitude, longitude and locating a place

Intuition

Every place on Earth is fixed by two numbers. LATITUDE measures how far north or south of the Equator you are (0° at the Equator, 90° at the poles) — bigger latitude means closer to a pole. LONGITUDE measures how far east or west of the Prime Meridian (0°) you are. So to ask 'which place is northernmost', you simply compare latitudes: the one nearest the North Pole wins.

Definition

  • Latitude — angular distance north or south of the Equator (0° to 90°). Higher north latitude = farther north.
  • Longitude — angular distance east or west of the Prime Meridian (0° to 180°).
  • 'Northernmost' = the location with the highest northern latitude. Among South-Asian capitals, New Delhi (~28.6° N) lies north of Kathmandu, Thimphu and Dhaka.

Worked example

Of four South-Asian capitals — New Delhi, Kathmandu, Thimphu, Dhaka — which is the northernmost?
Practice this conceptself-check · 3 quick reps

From the bank · past-year question

Example 1World and Human GeographyMODERATE
Which one among the following is the northernmost geographical location?

[Q92 · Apr · 2023]

Concept 2 of 3

Longitude, GMT offsets and the Prime Meridian

Intuition

The Earth turns 360° in 24 hours, so it sweeps 15° of longitude every hour — that is why local time changes as you move east or west. Greenwich (0° longitude) sets Greenwich Mean Time; a place to the east is AHEAD of GMT, a place to the west is BEHIND. So among a group of countries, the one whose standard meridian is farthest EAST of Greenwich has the largest positive time difference from GMT. The Prime Meridian itself (0°) is a geography fact: it runs through a fixed string of countries, so a question can ask which listed country it does NOT cross.

Definition

  • The Earth rotates 15° of longitude per hour (360° in 24 hours), so 1° ≈ 4 minutes of time.
  • Places east of Greenwich are ahead of GMT; places west are behind.
  • Among India, Nepal, Sri Lanka and Bhutan, Bhutan lies farthest east, so it has the maximum time difference from GMT.
  • The Prime Meridian (0°) crosses several African countries — including Algeria, Mali and Ghana — but NOT Morocco.

Worked example

Of India, Nepal, Sri Lanka and Bhutan, which has the maximum time difference from GMT?
Practice this conceptself-check · 3 quick reps

From the bank · past-year question

Example 2World and Human GeographyMODERATE
Which one of the following countries has the maximum time difference from Greenwich Mean Time (GMT)?

[Q67 · Sep · 2021]

East = ahead, but the DATE line is the opposite

Moving east of Greenwich puts you AHEAD in time — but crossing the International Date Line going east makes you set the clock BACK a day. Keep the two ideas separate (see the next concept).
Drill 1 more on longitude, gmt offsets and the prime meridian

Concept 3 of 3

The International Date Line

Intuition

The International Date Line (IDL) runs roughly along the 180° meridian, opposite the Prime Meridian. It is where the calendar date changes. The rule reverses what you expect from time: when you fly EAST across the IDL you SUBTRACT a day (you 'lose' 24 hours, i.e. repeat the date); flying WEST across it you ADD a day. The NDA tests exactly this 'east across the IDL = lose 24 hours' fact.

Definition

  • The International Date Line follows about the 180° meridian and is where the calendar date changes.
  • Crossing the IDL travelling EAST → set the date back one day (you 'lose' 24 hours).
  • Crossing the IDL travelling WEST → set the date forward one day (you 'gain' 24 hours).

Worked example

What happens to your calendar date when you fly WEST across the International Date Line?
Practice this conceptself-check · 3 quick reps

From the bank · past-year question

Example 3World and Human GeographyMODERATE
What will happen if you are flying east across the International Date Line?

[Q94 · Sep · 2022]

East across the date line LOSES 24 hours

Intuition says 'east = ahead = gain', but for the International Date Line it is the opposite: flying EAST across it you lose 24 hours (set the date back). West across it you gain a day.

Summary — formulas & gotchas at a glance

A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.

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4 questions from the bank — paginated, with cart and Word-export support.

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