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An aircraft departs from position A 04°10’S, 178°22’W and flies northward following the meridian for 2950 NM. It then flies westward along the parallel of latitude for 382 NM to position B.

What are the coordinates of position B?

  • A
    53°20’N, 172°38’E
  • B
    45°00’N, 172°38’E
  • C
    53°20’N, 169°22’W
  • D
    45°00’N, 169°22’W

Flying north along a meridian for 2,950 NM = an angular change of 2,950' (minutes of arc) = 49° 10'
49° 10' north of 04° 10' S = 45° 00' N
Flying along a Parallel of Latitude requires use of the Departure formula.
Departure (Distance) = Change of Longitude (') x Cosine of Latitude
382 NM = ChLong x Cosine 45°
382 NM = ChLong x 0.707
ChLong = 382 / 0.707
ChLong = 540.3' = 9°

Flying West along a Parallel of Latitude from 178° 22' W would take us to 187° 22' W but westerly Meridians only go up to 180° W, so as this is greater than 180° we need to subtract it from 360° to find out the Easterly Meridian.

360° 00' - 187° 22' = 172° 38'E
Therefore, B = 45° 00' N 172° 38'E

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