15 / 20
Due to the rotation of the earth, the apparent drift of a directional gyro with a N-S spin-axis at a latitude of 30°N is:
  • A
    2° per hour to the right.
  • B
    7.5° per hour to the right.
  • C
    11° per hour to the left.
  • D
    15° per hour to the left.
The gyro is initially aligned with a given meridian, but over time this meridian has moved due to Earth’s rotation, so the gyro is not correctly aligned anymore.

Apparent wander due to Earth’s rotation can be calculated using the following formula:

Apparent wander (°/h) = 15 x sin (latitude)


Therefore, at 30°N the apparent drift due to Earth’s rotation would be:
15 x sin (30°) = 7.5°/h

The apparent wander due to Earth’s rotation is always to the right in the northern hemisphere, and to the left in the southern hemisphere.

Your Notes (not visible to others)



This question has appeared on the real examination, you can find the related countries below.

  • Azerbaijan
    1
  • Hong Kong
    1
  • Pakistan
    1
  • Switzerland
    1
Keyboard Shortcut Use Keyboard Shortcuts