# Gyro Error

I’m getting lot of mixed advice so thought I would see what is out here about Gyro Error. Do you add it or subtract it ?? I understand, TVMDC, and CDMVT or correcting and uncorrecting. It seems to me that going to Gyro from true would be considered correcting therefore add E subtract W and vice versa if for some reason you would uncorrect from Gyro ?? Any Advice would be much appreciated.

I always go with “true is less when the error is west”

I recall just Treating it like a magnetic compass. Same theory, substitute gyro error rather than deviation/variation. Compass and true stay the same.

Gyro error is constant. Deviation varies with the heading. the same virgins and whiskey still apply.

Gyro least…error East.

[QUOTE=capcory;171913]I’m getting lot of mixed advice so thought I would see what is out here about Gyro Error. Do you add it or subtract it ?? I understand, TVMDC, and CDMVT or correcting and uncorrecting. It seems to me that going to Gyro from true would be considered correcting therefore add E subtract W and vice versa if for some reason you would uncorrect from Gyro ?? Any Advice would be much appreciated.[/QUOTE]

G E T V M D C add West or C D M V T E G add East. It works the same, just an extended version of the acronym. Gyro is only ever separated from true by gyro error so you put it on the end that has your true.

Gyro (G), Gyro Error (E), True (T), Variation (V), Magnetic (M), Deviation (D), Compass © add West

Compass ©, Deviation (D), Magnetic (M), Variation (V), True (T), Gyro Error (E), Gyro (G) add East

When comparing gyro heading to true heading and doing the math in this order:
Gyro G
[U]error E. (+ east. -west)[/U]
true. T

Bowditch paraphrased ; if the Gyro error is east the readings are too low and if it is West they are too high. Thus if Gyro error is 1° West, 1° is subtracted from all readings of the gyro compass to find the true heading or bearing.

Now with your true T heading or bearing you can move on to finding CE
when doing the math in this order from top down add west subtract east
If you do the math C D M V T starting with C at the top you add east and subtract west
T true
V. Variation. +w -e
M. Magnetic. From compass rose on chart
D. Deviation +w -e
C. Compass Looking at compass in wheelhouse
CE mag compass error equals sum of D and V 1e + 1w =0.
1 e + 4 w = 3 w. 5e + 1 w= 4 e

So much in the testing goes back to this knowledge. I would write it in the same order every time regardless as to what they are asking or supplying for info. Also I believe it is in the section of Bowditch that you will have on your desk on the exam room so know where to find it!

True to Compass add west, Compass to True add east. It doesn’t matter if the compass is magnetic or gyro, the same correction applies.

Good Day,

Not sure this the right place to mention the application for calculating the gyro, compass error…
I’m developer of the one - “Gyro Mate”, which works on android devices and it is free.
As ex-deck officer (did java coding also while offshore) decided to make this kind of application that I was missing on watch sometimes…
So, I hope this app will be useful for anyone on the bridge.

once you have more than 1 gyro on board you find out a gyro error is not constant in 360 degrees
Where’s your card in all this?

[QUOTE=powerabout;186053]once you have more than 1 gyro on board you find out a gyro error is not constant in 360 degrees
Where’s your card in all this?[/QUOTE]

While comparing gyroes there will be always a difference in data between devices and it is normal (when relatively small).
You mean a card similar to what we have for magnetic compass (deviation card)?

Error West compass Best
Error East Compass Least

If you just meditate in that rhyme for a little while you’ll never have a problem again…

Assume a desired course of 090 degrees True
So if GE= 2 degrees West
Gyro course would be 092 (best… Greater than true)

If GE = 2 degrees East
Gyro course to steer for 090 true would be 088 least… Less than true)