FlightDesk Aero / Question bank / PPL · Navigation / Distance along a meridian
PPL · EASA 061 · Basics of navigation
Distance along a meridian
Two airfields lie on the same meridian, at 47°25'N and 48°55'N. What is the distance between them?
Explanation
Along a meridian, one minute of latitude is one nautical mile. That is how the nautical mile was defined, which makes north–south distances the easiest sum in navigation: count the minutes of latitude and you have the miles. In the formula, d is the distance and Δφ the change of latitude.
Step by step
- Count up from A to the next whole degree: 47°25' → 48°00' = 35'.
- Then on to B: 48°00' → 48°55' = 0°55' = 55'.
- Total: 35' + 55' = 90'. One minute of latitude is one nautical mile: 90 NM.
Why not the other answers
- 150 NM treats a degree as if it had 100 minutes: 1°30' becomes 1.5 × 100. A degree has 60 minutes, so 1°30' is 90'.
- 60 NM counts only the whole degree and forgets the extra 30 minutes.
- 167 is the distance in kilometres (90 × 1.852 ≈ 167 km), not in nautical miles.
Tip. Only latitude works this way. A minute of longitude shrinks towards the poles, so east–west distances need the cosine of the latitude.
Original questions written by FlightDesk Aero and aligned with the EASA syllabus. They are not questions from the official EASA exam bank.