Gyrocompass for knowing the true North


A gyrocompass is one of the most essential marine equipment on board now. Working under a simple physics law, it has changed how mariners navigate. Gyroscope needs to be maintained correctly for yielding accurate and precise results.



Gyro compasses are devices installed on ships to detect the true north. True north is different from magnetic north. They work on the principle of simple physical laws of gravity and earth’s rotation. They are widely installed on all ships to guide them in the proper channel and has become one of the indispensable instruments. Gyroscope inside a gyrocompass is made to flow freely over three mutually perpendicular axes. The compass is controlled to enable the axis of spin to settle parallel with the true meridian.


The external magnetic field doesn’t affect gyrocompass. When a ship changes its course, an independently driven mechanism called ‘Phantom’ moves along while the rotor system continues to follow the northward direction. This difference in direction sends a signal to the driving motor which moves the phantom step in the rotor system. As soon as they are aligned, electrical impulses are sent by the phantom to the repeater compasses for each degree it traverses.


Gyrocompass system works on two fundamental characteristics, they are


  • Gyroscopic Inertia:
    The tendency of any object to continue in the state of rotation on its plane.
  • Precession:
    Precession causes the gyroscope to move when a couple is applied. It moves at right angles to the axis of the applied couple and also the spinning wheel.


These two characteristics along with earth’s natural forces, rotation and gravity, enables the gyrocompass to seek the true north.  Once settled on the true meridian the rotor indefinitely will remain there as long as the electrical supply of the ship remains constant, unaltered and unaffected by external forces.


Ships use gyrocompass to detect the true north, steer, find the position and record the navigational course. Ship’s course, speed and latitude may cause errors in the gyrocompass. On a northern navigational course, the compass will be slightly deflected to the west of the meridian and on a southern course, it is deflected to east.


Modern ships have advanced GPS system installed that feed data to the gyrocompass for correcting the error. An orthogonal triad of fibre optic design and also ring laser gyroscopes which apply the principles of an optical path to determine the rate of rotation. This avoids the usage of any mechanical component eliminating flaws and detects true north.




  • Check repeater with the master compass to ensure its accuracy. In case of power failure, it is advised to reset the repeater.
  • Check the compass error with azimuth.
  • Speed and latitude should be reset as necessary.
  • Thoroughly inspect the compass for any damage.
  • Once in a month check the alarm buzzer.
  • Clean the equipment and follow the instruction on the manual.
  • General check-up and repair can be done.