How do Fibre Optic Gyroscopes Determine Geographic North?

Question

I understand that 2 beams/waves of coherent light are injected into the fibre optic coil in opposite directions, and that the coil is spinning at a specific rate and forces one of the waves to travel a further distance; and upon return the waves will be incoherent and out of phase.  I also understand that interferometry is used to measure this difference in phase, but after all the reading that I have done, I have not found an explanation of how this relates to finding north.  I am attempting to write a paper in layman's terms for the masses of my workplace and am having some difficulty. Can anyone explain it to me in layman's terms?

Anonymous · Answer

any "gyroscopic", that is rotational effect, is based on the idea of "conservation of angular momentum'.  just as a mss will "keep moving" unless acted on by a force,
anything that spins will maintain is axis of rotation in the same 3 D direction is space ( unless space is warped by gravity)  unless acted on any and external torque. the math is three dimension vector math which is "strange" to most of us
thus a gyro has to be "aligned" at start.  it does NOT 'point north" it keeps its point position

since nothing is perfect any real gyro (ball) will precess or drift due to tiny unbalanced forces and torques.

light is more subtle and depends on einstein special thoery of relativity. light does what it does becuse it is light.  we understand a little but not everything

the light detectors change the light when detected so it gets to be a serious engineering problem ( in other words I do' kno)

Anonymous · Answer

No gyroscope determines north.  All a gyroscope does is provide a stable reference orientation (direction).  If you want it to point north, you have to point it there before you activate it.

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How do Fibre Optic Gyroscopes Determine Geographic North?

2 Answers