Post by aliveandkicking on Apr 18, 2015 9:48:49 GMT
These devices need a small latitude adjustment to avoid an error created by one end of the gyro travelling faster due to a spinning earth than the other end which is not so far north.
The error is reversed either side of the equator. (on a globe the fastest rotation is at the equator)
maritime.org/doc/gyromk14/index.htm#pg1a
" 50. As we move the compass further north, the north end of the gyro axle turns to the east faster and rises faster, and for this reason the compass must be precessed faster toward the meridian. The downward pressure on the south end of the axle is correspondingly greater, the torque about the vertical axis is greater, the north- end precesses down faster, and the gyro consequently settles further to the east.
51. South of the equator the effect of the earth's rotation on the gyro is just the opposite: here the south end of the axle tends to rise and turn to the east; the excess mercury is in the north containers, precessing the north end to the east toward the meridian. Torque about the vertical axis is reversed so that the south end is being precessed down at the same rate as the horizontal component of the earth's rotation is tilting it up. Therefore the north end of the axle lies slightly to the west of the meridian.
52. The small angle at which the gyro axle settles from the meridian varies with the latitude, and for this reason a correction must be introduced which will compensate for this natural error at any latitude where the compass may be expected to be used.
53. From zero at the equator, this error increases to 2.9 degrees at 60 degrees north or south latitude; it is easterly in north latitudes and westerly in south latitudes.
54. No attempt is made in the gyro-compass to compel the axle to seek a resting place at variance with its natural settling position. Instead, a latitude adjustment is provided which moves the lubber-ring the necessary amount to cause the compass indication to be true."
The ships compass therefore shows the same kind of conundrum for a flat earth as the rotating stars do in the southern hemisphere
The error is reversed either side of the equator. (on a globe the fastest rotation is at the equator)
maritime.org/doc/gyromk14/index.htm#pg1a
" 50. As we move the compass further north, the north end of the gyro axle turns to the east faster and rises faster, and for this reason the compass must be precessed faster toward the meridian. The downward pressure on the south end of the axle is correspondingly greater, the torque about the vertical axis is greater, the north- end precesses down faster, and the gyro consequently settles further to the east.
51. South of the equator the effect of the earth's rotation on the gyro is just the opposite: here the south end of the axle tends to rise and turn to the east; the excess mercury is in the north containers, precessing the north end to the east toward the meridian. Torque about the vertical axis is reversed so that the south end is being precessed down at the same rate as the horizontal component of the earth's rotation is tilting it up. Therefore the north end of the axle lies slightly to the west of the meridian.
52. The small angle at which the gyro axle settles from the meridian varies with the latitude, and for this reason a correction must be introduced which will compensate for this natural error at any latitude where the compass may be expected to be used.
53. From zero at the equator, this error increases to 2.9 degrees at 60 degrees north or south latitude; it is easterly in north latitudes and westerly in south latitudes.
54. No attempt is made in the gyro-compass to compel the axle to seek a resting place at variance with its natural settling position. Instead, a latitude adjustment is provided which moves the lubber-ring the necessary amount to cause the compass indication to be true."
The ships compass therefore shows the same kind of conundrum for a flat earth as the rotating stars do in the southern hemisphere
