Magnetic declinations changing?
 

Something tells me we're going to see a notice to mariners next year on this...

http://www.breitbart.com/news/2005/12/09/D8ED22880.html

The present navigational compass would no longer be accurate. The face plate would need to be shifted to get a true reading of North but I'm sure there is more to be considered. An enhanced digital compass or GPS is useless w/o power.

Anyone know how far off a compass would be by moving the N pole 1000 miles?

While returning from from fishing in Vineyard Sound in early summer, I noticed that the magnetic course that I usually steer to get from point A to point B seemed to have me heading in the wrong direction. I thought that maybe there was something on the dash throwing my compass off such as a plug or a knife or something, but that wasn't the case. The same was true on a subsequent trip about a week later, and I was going nuts trying to figure out why my compass seemed to suddenly be off.
About a week later I read that after a slow and steady shift towards the NW, the pole had taken a dramatic jump from the Arctic Ocean to somewhere NW of Alaska.

My compass seemed to be off by about 7°. There are services here in NB that regularly set the deviation between true & magnetic N for the compasses on fishing vessels.

Relax guys, this shift has been over the last 150 years. According to NOAA, the shift around here is 3' per year. It will take 20 years to change the declination 1 degree.

Morone, I think you need to have your compass swung by a pro. Maybe one of your compensators got whacked out of adjustment.

Apparantly so

Given: 1) one side of a triangle (y= 10,000 ft.)
2) diameter earth from north to south of
which I don't know off the top of head
(x= ???? ft)

angle equal to (arctan 10,000/????)

The face plate is shifted by that angle.

It all depends what your navigating and the distance of your navigating. If your traveling from the south pole to the north pole your going to be off by 10,000 ft. But if your traveling short distance that is to say, a few hundred miles then your target is only a negligible distance away. Now of course a missle it would be significant.

That is probably why we missed the fall run the magnetic fiels shift. :rotf2:

You should have this done regardless anytime you install a compass.

Unless of course you really like rocks.

sallty
the diameter of earth is 7900 mi.
10,000 is about 2 mi

arctan(2/7900) = .0145 degree

not even 2 hundredith of a degree

Compass was swung when first installed.

I would never rely on just a compass to stay clear of rocks. I've been a crew member on commercial fishing vessels since the late seventies and operating them since the late eighties. I've been operating my own pleasure craft in and around Buzzard's Bay, The Elizabeths and Vineyard Sound since the mid eighties, including more times than I wish in dense fog with no radar.

I haven't run aground :point: (yet).

Redsoxticket thanks for that info, I learned something today.

this is nothing new...
look on any chart... in any one of the compass roses...
says right there "anual deviation of {blank} degrees".

basic plotting skills everyone should know.
T-rue
V-ariation
M-agnetic
D-eviation
C -mpass


calibrating your compass yourself isn't that hard either.
look in chapmans piloting...

but with gps today,, it's all forgotten...

This is very "true". But everyone in small craft should just stick to magnetic courses from the get go. All teaching schools from Mass Maritime to the Mom and Pop navigating classes will always make you convert your course to true. They do this for only one reason. Because the USCG wants it that way when they test you. But on a small boat you will never use this. Start it and keep it in magnetic, then you won't make a mistake.

On the big ship we always use True, because we have 2 gyro compasses that cost tens on thousands$$ and very accurate.

T rue
V irgins
M ake
D ull
C ompany

Anyone know a compass guy that can replace the seals and refill a C-plath compass?