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What is the apparent drift experienced by a directional gyro with a north-south spin axis at a latitude of 45°N due to the rotation of the Earth?

  • A

    7° per hour to the left.

  • B

    15° per hour to the left.

  • C

    11° per hour to the right.

  • D

    2° per hour to the right.

Apparent drift due to earth rate is at a maximum of 15 deg/hr at the poles. It can be calculated at any latitude

  • Apparent drift = 15 x Sin Lat.

In the Northern hemisphere the drift of the gyro axis is clockwise/right-hand and the indicated heading reduces.

By convention, a negative sign is used to show this.

So, after the implementation of the formula:

  • 15 x sin 45 = 10.5°/hr or 11° per hour to the right.

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