A Polar Stereographic chart is used for navigation. The straight line betweenA 75° 00′.0N, 166°00′.0E and B 78° 00′.0N, 154° 00′.0E is drawn on this chart. The True Track angle of the Rhumb line is 317°.
Calculate the direction T of the straight line in position A.
Refer to figure.
Rhumb Line track is 317º.
- Conversion Angle = Difference between the Rhumb Line Track and the Great Circle Track.
Conversion Angle = 1/2 Convergency.
On a Polar Stereographic: Convergence = Change Longitude
Convergence = 166ºE - 154ºE = 12°
Therefore, Conversion Angle = 12º / 2 = 6º
- GCT = RLT + Conversion Angle
GCT = 317°T + 6° CA = 323°T
(1) Establish the hemisphere. On a polar stereographic chart, in the northern hemisphere, Rhumb line is curved and concave to the North pole => RL lies to the south of the straight lline. Great circle is a straight line.
(2) Identify direction. Rhumb line track is 317º => "A" will be on the right; "B" on the left.
(3) Rhumb line track = 317º. As you can see on the attached figure, great circle track will be greater than 317º by the value of conversion angle: 317º + 6º = 323º.
Your Notes (not visible to others)
This question has appeared on the real examination, you can find the related countries below.