Compass Variation

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CJ1

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I’ve always been puzzled by compass variation- I would always miscalculate in the RYA theory and get the answer wrong cos I added instead of subtracted or vice versa. Anyway, I chanced across this article today:

Compasses to point true north for first time in 360 years

and am delighted to learn that for at least the next decade or so I can forget all about it because for the first time in 360 years magnetic and true are more or less aligned.

But I still have one question and wondered if any wise old sea dogs out there can provide an answer. Does the phenomenon of magnetic variation mean that eventually in the Distant future True North will become magnetic South and vice versa?
 
The drift in the north pole won't go that far, but at some time the whole thing will flip over, when north will become south & vice versa. This has happened numerous times in the past, as confirmed by magnetised rocks dug up from the oceans. I believe that it is not due to occur in the next week or two, so you can keep your compass.

I never found the old mnemonics about compasses helpful, such as 'west is best etc'. I prefer just to visualise the compass rose on the chart and work it out from there.
 
The variation in compass variation is large... You need to check the east coast specifically, but it's below a degree anyway as I recall, and show me a helmsman who can steer to a degree by compass...
 
Gladys said:
The variation in compass variation is large... You need to check the east coast specifically, but it's below a degree anyway as I recall, and show me a helmsman who can steer to a degree by compass...
Click to expand...
Exactly. If I were crossing an ocean, I would have a deviation card. For coastal and Channel sailing, I rarely look at my compass Apart from the occasional cross check with the plotter, but would be happy with whatever it told me if the plotter went tits.
 
Last edited:
CJ1 said:
I’ve always been puzzled by compass variation- I would always miscalculate in the RYA theory and get the answer wrong cos I added instead of subtracted or vice versa. Anyway, I chanced across this article today:

Compasses to point true north for first time in 360 years

and am delighted to learn that for at least the next decade or so I can forget all about it because for the first time in 360 years magnetic and true are more or less aligned.

But I still have one question and wondered if any wise old sea dogs out there can provide an answer. Does the phenomenon of magnetic variation mean that eventually in the Distant future True North will become magnetic South and vice versa?
Click to expand...
I had to learn the ditties. My brain wont compute it otherwise.
 
My chart says variation is decreasing by 9’ annually. Does that mean that in 1,020 years the variation will be 180 degrees, ie magnetic North will point South?
 
CJ1 said:
My chart says variation is decreasing by 9’ annually. Does that mean that in 1,020 years the variation will be 180 degrees, ie magnetic North will point South?
Click to expand...

No. (Or if it should transpire, it will be entirely coincidental.)

As I understand it, the magnetic pole wanders around somewhat randomly over the longer timescale. So it might well start decreasing faster, or slower, or begin increasing again.

Hopefully AntarcticPilot, who knows about these things, will be along to better inform us. If I remember correctly he previously said it is not known quite how quickly the 'flips' of the north and south magnetic poles happened in the past, only roughly when these took place.
 
Gladys said:
The variation in compass variation is large... You need to check the east coast specifically, but it's below a degree anyway as I recall, and show me a helmsman who can steer to a degree by compass...
Click to expand...

I managed it once...
On Steve Fossets Play Station ...


though TBF we were motoring in absolute calm withut a breath of wind.
 
Magnetic deviation is not consistent worldwide. I remember being somewhere in the Western Pacific a few years and dealing with a 45 degree magnetic variation. And I was trying to avoid one of those reefs in the middle of the ocean that are only just exposed at low tide.
 
Gladys said:
You missed one out Compass Deviation MAGNETIC Variation True...

Variation West Compass best, Variation East compass least
Click to expand...

You’re quite right. I added the explanation as an afterthought. (PS. Look at what time I was posting. I’d been up since 0500 taking Mrs M to hospital for a day case operation and couldn’t sleep.)

PS I wish people would stop saying variation when they mean deviation and vice versa. eg #13
 
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