gyrocompasses revisited

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vhu9644

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gyrocompasses revisited
« on: April 07, 2011, 10:59:22 PM »
when i first became a member, i questions about the gyrocompass.  the thread died very soon

i did some research, and now, i ask again, how does a gyrocompass keep pointing north in FE?

normally on RE, the ship is moving on a curved path, true, but the gyrocompass is built to rotate on its own plane, and hence is relitively uneffected by a round earth. the compass will turn to match becuase it points to the same direction on its plane
on a flat earth, however, the ship'g gyrocompass has to rotate on its plane to match with the north in the center.  how do you explain this?
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spanner34.5

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Re: gyrocompasses revisited
« Reply #1 on: April 08, 2011, 01:49:32 AM »
A gyro compass is regularly re set using the magnetic compass.

To answer your question it doesn't, whatever the shape of the Earth.
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Oracle

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Re: gyrocompasses revisited
« Reply #2 on: April 08, 2011, 09:01:14 AM »
Gyrocompasses may be occasionally set and checked by magnetic compasses, but they do not use magnetism to function after being set... ie. there are no regular resets built into the mechanism.

However, The crucial additional ingredient needed for a gyrocompass to seek out true north (over a simple gyroscope) is some mechanism that results in an applied torque whenever the compass's axis is not pointing north.

I can't immediately think of a way to make it work on a FE model, but neither do I know how to correct it for a RE model.  I'd have to say that this corrective torque is in question as to the reliability of the gyrocompass.

However, going back to how gyroscopes in general work.  Maybe they do not point to one direction in true-space as we have been told due to the conservation of angular rotation.  Maybe there is some quality of the sun itself that causes the gyroscope to want to try and track it's apparent position/path across the sky instead.

Not offering it as truth, but I think there needs to be a FE a theory about how gyroscopes work in general before a gyrocompass can be addressed adequately.

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berny_74

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Re: gyrocompasses revisited
« Reply #3 on: April 08, 2011, 09:30:45 AM »
More realistically a Gyrocompass on a ship would be checked against a celestial type observation as Magnetic compasses themselves have a fairly large error and are regularly checked "boxed" with fixed land navigation points.

Obviously with GPS involved the use of magnetic and gyro compasses are falling out of use and are being regulated to secondary navigation tools.

Berny
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spanner34.5

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Re: gyrocompasses revisited
« Reply #4 on: April 08, 2011, 09:57:27 AM »
More realistically a Gyrocompass on a ship would be checked against a celestial type observation as Magnetic compasses themselves have a fairly large error and are regularly checked "boxed" with fixed land navigation points.

Obviously with GPS involved the use of magnetic and gyro compasses are falling out of use and are being regulated to secondary navigation tools.

Berny
Bad memories of Gyro failure.

I bow to your greater nautical knowledge. However light aircraft gyros are regularly reset using magnetic compass.
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vhu9644

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Re: gyrocompasses revisited
« Reply #5 on: April 08, 2011, 10:45:23 PM »
More realistically a Gyrocompass on a ship would be checked against a celestial type observation as Magnetic compasses themselves have a fairly large error and are regularly checked "boxed" with fixed land navigation points.

Obviously with GPS involved the use of magnetic and gyro compasses are falling out of use and are being regulated to secondary navigation tools.

Berny
Bad memories of Gyro failure.

I bow to your greater nautical knowledge. However light aircraft gyros are regularly reset using magnetic compass.

ok, what about ships?  from what ive read, they arent frequently reset
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vhu9644

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Re: gyrocompasses revisited
« Reply #6 on: April 09, 2011, 10:13:00 PM »
also, gyrocompasses were invented in 1890, so you cant use gps and satelites to recalibrate it
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markjo

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Re: gyrocompasses revisited
« Reply #7 on: April 10, 2011, 07:17:25 AM »
also, gyrocompasses were invented in 1890, so you cant use gps and satelites to recalibrate it

???  Why can't modern gyrocompasses be recalibrated by GPS?  Also, wouldn't GPS make a gyrocompass redundant?
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vhu9644

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Re: gyrocompasses revisited
« Reply #8 on: April 10, 2011, 12:36:09 PM »
also, gyrocompasses were invented in 1890, so you cant use gps and satelites to recalibrate it

???  Why can't modern gyrocompasses be recalibrated by GPS?  Also, wouldn't GPS make a gyrocompass redundant?
they could, just they werent always calibrated by gps
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vhu9644

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Re: gyrocompasses revisited
« Reply #9 on: April 10, 2011, 05:45:44 PM »
have any FEers posted anything yet?
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berny_74

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Re: gyrocompasses revisited
« Reply #10 on: April 10, 2011, 06:31:05 PM »
also, gyrocompasses were invented in 1890, so you cant use gps and satelites to recalibrate it

???  Why can't modern gyrocompasses be recalibrated by GPS?  Also, wouldn't GPS make a gyrocompass redundant?

A ships heading will not always read out the same as its direction (true to GPS) that it is travelling.  Current wind waves etc will always cause a change of direction.  It is much easier to find a fixed heading relative to the ship and adjust that heading periodically as it is affected by differing factors.

Berny
Sailing also makes gyrocompass difficult to use as well.
To be fair, sometimes what FE'ers say makes so little sense that it's hard to come up with a rebuttal.
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vhu9644

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Re: gyrocompasses revisited
« Reply #11 on: April 12, 2011, 06:43:19 PM »
i dont think i have an answer yet...

how does a gyrocompass keep pointing north in FE?
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Oracle

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Re: gyrocompasses revisited
« Reply #12 on: April 12, 2011, 06:49:08 PM »
i dont think i have an answer yet...

how does a gyrocompass keep pointing north in FE?

Seasonally Cyclical Solar Rotational Orientation Theory?!?!?  (SCSROT)

:P
« Last Edit: April 12, 2011, 06:52:43 PM by Oracle »

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Ski

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Re: gyrocompasses revisited
« Reply #13 on: April 12, 2011, 07:06:55 PM »
i dont think i have an answer yet...

how does a gyrocompass keep pointing north in FE?

Considering a gyrocompass doesn't keep pointing north, I'm not sure how to respond.
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Oracle

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Re: gyrocompasses revisited
« Reply #14 on: April 12, 2011, 07:49:27 PM »
i dont think i have an answer yet...

how does a gyrocompass keep pointing north in FE?

Considering a gyrocompass doesn't keep pointing north, I'm not sure how to respond.

It isn't perfect, but they are pretty good at attempting to keep a directional of true north without the use of magnetism or celestial coordinates once set.  Perhaps you are thinking of a gyroscope instead?

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Ski

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Re: gyrocompasses revisited
« Reply #15 on: April 12, 2011, 08:25:42 PM »
They need constant adjustment to continue to point north. Gyro-drift has accounted for innumerable deaths among sailors and aviators. If I need to adjust it daily (or hourly depending on latitude and velocity), it doesn't "keep pointing north". If it has to be slaved, it doesn't "keep pointing north."
"Never think you can turn over any old falsehood without a terrible squirming of the horrid little population that dwells under it." -O.W. Holmes "Truth forever on the scaffold, Wrong forever on the throne.."

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vhu9644

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Re: gyrocompasses revisited
« Reply #16 on: April 12, 2011, 08:31:07 PM »
They need constant adjustment to continue to point north. Gyro-drift has accounted for innumerable deaths among sailors and aviators. If I need to adjust it daily (or hourly depending on latitude and velocity), it doesn't "keep pointing north". If it has to be slaved, it doesn't "keep pointing north."
you have used one? becuase some sailors i have met say differently.
and hourly/daily is not occacional, which is what other sources have stated
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Ski

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Re: gyrocompasses revisited
« Reply #17 on: April 12, 2011, 08:59:02 PM »
Quote from:  Dutton's Nautical Navigation
When a ship is at sea, the navigator should determine the gyrocompass error at least once each day; this is required for naval vessels and is desirable on any ship. Over and above this bare minimum, the prudent navigator will take advantage of every opportunity to check the accuracy of his gyro. The importance of so doing is emphasized by a grounding case on record where the failure of a ship's gyro went undetected for a period of over twelve hours, with the result that, at the time of grounding the vessel was more than 110 degrees off course and more than 200 miles out of position.


The drift is even more pronounced in flight.
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berny_74

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Re: gyrocompasses revisited
« Reply #18 on: April 12, 2011, 09:00:39 PM »
They need constant adjustment to continue to point north. Gyro-drift has accounted for innumerable deaths among sailors and aviators. If I need to adjust it daily (or hourly depending on latitude and velocity), it doesn't "keep pointing north". If it has to be slaved, it doesn't "keep pointing north."

Magnetic Compasses have to be adjusted as well.  They can deviate radically depending on certain situations.  A gyrocompass that is checked against celestial fixes is much more accurate than a magnetic compass.
 
Berny
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Ski

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Re: gyrocompasses revisited
« Reply #19 on: April 12, 2011, 09:03:36 PM »
Magnetic Compasses have to be adjusted as well.  They can deviate radically depending on certain situations.  A gyrocompass that is checked against celestial fixes is much more accurate than a magnetic compass.
 
Berny
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Absolutely. Which is why celestial nav should still be taught, but isn't (in aviation circles anyway).
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vhu9644

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Re: gyrocompasses revisited
« Reply #20 on: April 12, 2011, 09:03:59 PM »
Quote from:  Dutton's Nautical Navigation
When a ship is at sea, the navigator should determine the gyrocompass error at least once each day; this is required for naval vessels and is desirable on any ship. Over and above this bare minimum, the prudent navigator will take advantage of every opportunity to check the accuracy of his gyro. The importance of so doing is emphasized by a grounding case on record where the failure of a ship's gyro went undetected for a period of over twelve hours, with the result that, at the time of grounding the vessel was more than 110 degrees off course and more than 200 miles out of position.


The drift is even more pronounced in flight.
i havent seen a flight, and also, someone above mentioned that they are constantly adjusted.
i am talking about ships

and berny posted this when i first asked

Gyro compasses are unreliable in the polar regions as well as magnetic compasses.  This is due to the earth's rotation.  A gyroscope is fixed to a position in outerspace - not to a point on the earth.
Quote from: http://en.wikipedia.org/wiki/Gyrocompass
Another, more practical, method is to use weights to force the axis of the compass to remain horizontal with respect to the Earth's surface, but otherwise allow it to rotate freely within that plane. In this case, gravity will apply a torque forcing the compass's axis toward true north. Because the weights will confine the compass's axis to be horizontal with respect to the Earth's surface, the axis can never align with the Earth's axis (except on the Equator) and must realign itself as the Earth rotates. But with respect to the Earth's surface, the compass will appear to be stationary and pointing along the Earth's surface toward the true North Pole.

In fact - on further reading - a gyrocompass actually proves the earth is spinning by the requirements and effects of dampening and the amount of errors that can occur.  In fact a gyrocompass seems to be an extremely complicated fit of machinery compared to the gyroscope.  Perhaps Thork can elaborate more on uses and error fixes as he would use them on aircraft.  I used a marine gyrocompass but besides the few times it broke down its use was limited by the fact that we were a sailboat.

Berny
This is interesting


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Ski

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Re: gyrocompasses revisited
« Reply #21 on: April 12, 2011, 09:07:02 PM »
All of that is correct; which is why I said a gyrocompass does NOT keep pointing north.
"Never think you can turn over any old falsehood without a terrible squirming of the horrid little population that dwells under it." -O.W. Holmes "Truth forever on the scaffold, Wrong forever on the throne.."

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vhu9644

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Re: gyrocompasses revisited
« Reply #22 on: April 12, 2011, 09:09:17 PM »
they are set to north, and point there.
but its misdirection is caused by the earrth's rotation, which FE does not have
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Ski

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Re: gyrocompasses revisited
« Reply #23 on: April 12, 2011, 09:18:02 PM »
they are set to north, and point there.
but its misdirection is caused by the earrth's rotation, which FE does not have
Your original question was:

how does a gyrocompass keep pointing north in FE?




There are six or so causes of gyro error that have nothing to do with the earth's alleged rotation. Shall we gloss over that?
"Never think you can turn over any old falsehood without a terrible squirming of the horrid little population that dwells under it." -O.W. Holmes "Truth forever on the scaffold, Wrong forever on the throne.."

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vhu9644

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Re: gyrocompasses revisited
« Reply #24 on: April 12, 2011, 09:20:20 PM »
they are set to north, and point there.
but its misdirection is caused by the earrth's rotation, which FE does not have
Your original question was:

how does a gyrocompass keep pointing north in FE?




There are six or so causes of gyro error that have nothing to do with the earth's alleged rotation. Shall we gloss over that?

sorry, would you like me to start a new thread about the new problems?
and what are the 6 or so errors not caused by earth's rotation?

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Ski

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Re: gyrocompasses revisited
« Reply #25 on: April 12, 2011, 09:23:16 PM »
Gimbal error, Ballistic damping and deflection errors, Quadrantal error... I may be missing some.
"Never think you can turn over any old falsehood without a terrible squirming of the horrid little population that dwells under it." -O.W. Holmes "Truth forever on the scaffold, Wrong forever on the throne.."

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vhu9644

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Re: gyrocompasses revisited
« Reply #26 on: April 12, 2011, 09:26:16 PM »
please elaborate on them.  didnt see that when i searched up gyrocopasses
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berny_74

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Re: gyrocompasses revisited
« Reply #27 on: April 12, 2011, 09:34:40 PM »
Gimbal error, Ballistic damping and deflection errors, Quadrantal error... I may be missing some.

#1 Human Error


Many errors now have become moot with GPS and optical devices for error correction.  On board a ship a Gyro will still outperform a magnetic compass. 
 

Berny
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Ski

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Re: gyrocompasses revisited
« Reply #28 on: April 12, 2011, 09:43:06 PM »
Gimbal error is when the plane (or ship) is not perfectly horizontal to the earth when the reading is taken. Ballistic deflection occurs when there is an acceleration in the North or South plane. Damping is related to any change of course or speed. Quadrantal error has to due with the balance of the gyro when in turbulence.

#1 Human Error

And that, or course...
"Never think you can turn over any old falsehood without a terrible squirming of the horrid little population that dwells under it." -O.W. Holmes "Truth forever on the scaffold, Wrong forever on the throne.."

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vhu9644

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Re: gyrocompasses revisited
« Reply #29 on: April 12, 2011, 09:46:20 PM »
Gimbal error is when the plane (or ship) is not perfectly horizontal to the earth when the reading is taken. Ballistic deflection occurs when there is an acceleration in the North or South plane. Damping is related to any change of course or speed. Quadrantal error has to due with the balance of the gyro when in turbulence.

#1 Human Error

And that, or course...
i read that there is a corrector in there for gimbal error
how does ballistic deflection and damping happen?
also, i read that gryocompasses are fixed so they only rotate one direction
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