Oxford, Air Navigation
Convergency and Conversion Angle: DGCA Air Navigation questions
Convergency is the angle between two meridians, change of longitude times the sine of mean latitude, and it is how much a great circle track changes end to end. Conversion angle is half of it, the gap between great circle and rhumb line at each end.
Here 18 questions turn on track geometry: find one track from the other, work the return track, or name the hemisphere from two tracks. Exam sessions have put 1 of this set to candidates.
Use full convergency between the two ends of a great circle and the conversion angle against the rhumb line. The great circle lies on the polar side, so in the north an eastbound initial great circle track is less than the rhumb line track. Southern signs reverse.
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Question 1 of 5
The convergency of the meridians through M and N, both in the Southern hemisphere, is 12°. The rhumb line track from M to N is (249°T). What is the initial great circle track from M to N?
Question 2 of 5
The convergency of the meridians through M and N both in the Southern hemisphere is 12°. The rhumb line track from M to N is (249°T). What is the GREAT CIRCLE track from N to M? The reciprocal/return journey
Question 3 of 5
Position A is at 30°00'S 165°00'E. The great circle bearing of position B also at latitude 30°00'S from A is (100°T). What is the great circle track from B back to A?
Question 4 of 5
Position A is at 30°00'S 165°00'E. The great circle bearing from A to position B also at 30°00'S is (100°T). The great circle track from B to A is (260°T). What is the longitude of position B?
Question 5 of 5
Position D is at 30°00'N 179°00'W. The rhumb line from D to C is (090°T) due East. The initial great circle track from C to D is (287°T). What is the great circle track from D to C?
13 more questions in this chapter
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