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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.

  • A
    311°
  • B
    329°
  • C
    323°
  • D
    305°

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
At "A" Great Circle Track > Rhumb Line Track (refer to figure).
  • 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.

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