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On a Polar Stereographic chart, the initial great circle course from 70°N, 060°W to 70°N, 060°E is approximately…
  • A
    150° T
  • B
    210° T
  • C
    030° T
  • D
    330° T

Refer to figure.

Draw a diagram:

  1. Draw the circle with 70ºN latitude

  2. Mark the three local meridians

A – 060ºW
B – 060ºE
Greenwich Meridian (000ºE/W) – DATUM meridian

  1. Draw a straight line between A – B, representing the GCT

  2. A and B are of the same latitude => Rhumb line track is 090ºT

The difference between true track at A and B = conversion angle which equals ½ Convergency

Note: on a polar stereographic chart, convergency is always the same to the change in longitude

Convergency = change of longitude
Convergency = 120º
Conversion Angle = ½ x 120º = 60º

Therefore, GCT = RLT – conversion angle
GCT = 090ºT – 060º = 030ºT

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