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Magnetic North Pole

supersailor

Contributing Partner
Throw away your deviation tables. The magnetic north pole has been wandering all over the place and it seems to be determined to reach Siberia soon. The rate of change is accelerating rapidly which means that that compass on the binnacle is not pointing where it used to. It appears now that an update of the deviation table every couple of months might be prudent.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
So do not travel too far... North...

It is certainly a real concern for anyone navigating higher than 55 degrees, per an article today.
https://www.cnn.com/2019/02/05/health/north-pole-magnetic-moving-russia-scli-intl/index.html

This might be an appropriate time for boat owners to have their compass swung. When I had ours rebuilt and swung a few years ago, that was the fist time ever for any formal maintenance on it since the boat was built in 1988.
I wonder how many other owners have ever had this done? :rolleyes:

http://www.ericsonyachts.org/infoexchange/entry.php?87-Compass-Restoration

Something to do for sure before you head up the Inland Passage this summer.
 

toddster

Curator of Broken Parts
Blogs Author
This is a good illustration of how hard it is to present a science story to the popular press. At the time that I regularly dealt with them, there were perhaps three full-time newspaper science reporters in the USA with enough background in science and nature to understand and accurately report something like this. Since then, newspaper budgets have evaporated and of course the internet has weaponized hyperbole. Here's how it goes. The very concept of a magnetic north pole is new to most nooze writers. The fact that it moves just blows their minds. And we haven't even gotten to the story yet. Which is that the people who keep track of those movements recently guessed wrong about how it was going to move during the current five year period, and had to issue an update. Wow. Three exponentially-stacked new concepts, and the headlines get apocalyptic.

The story I got from the scientific press was that at the time of the last five-year update, movement of the magnetic pole appeared to be decelerating. However, instead it accelerated back to (so far) about the same speed and direction that it has been moving for decades. So the models used for mapping were updated early, instead of waiting for five years as usual. For most of us, five years is still frequently enough.
 

bgary

Advanced Beginner
Blogs Author
Three exponentially-stacked new concepts, and the headlines get apocalyptic.

and, well, there might actually be a fourth one... an article I read indicated that the reason for the (unpredictable? accelerated?) movement of the magnetic north pole is thought to be related to a high-velocity "jet" deep within the magma pool. Causing the reporter to wonder whether this signaled A Bad Thing related to the ring of volcanoes all around the Pacific rim.

So there's that....
 

supersailor

Contributing Partner
One little note, When I moved into my house in 2007 The axis of the house was exactly on the north-south axis of magnetic north. Now, it is off by about 4 degrees. Could that be enough to cause problems while attempting to avoid rocks in a heavy fog? I'll reswing the compass.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
One little note, When I moved into my house in 2007 The axis of the house was exactly on the north-south axis of magnetic north. Now, it is off by about 4 degrees. Could that be enough to cause problems while attempting to avoid rocks in a heavy fog? I'll reswing the compass.

I have seen that house! Looks very solid to me.... so I doubt that it rotated on its axis. :0

On the plus side it's a good time for all of us "northern" sailors to have our compass' swung. I hope that other owners post up their experiences and if the adjuster had to make much of an adjustment.
 

GrandpaSteve

Sustaining Member
On how many boats is the ship's compass the only compass? Off the top of my head I have:
- Ships Compass
- Hand-held GPS Compass
- Hand Bearing Compass
- iPhone Compass
- Chart Plotter bearings (when moving)
- Auto-helm compass
- Binocular compass
- OpenCPN GPS Bearings

So what is the value these days of professional swinging of the ships compass?

Thanks,
Steve
 
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Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
On how many boats is the ship's compass the only compass? Off the top of my head I have:
- Ships Compass
- Hand-held GPS Compass
- Hand Bearing Compass
- iPhone Compass
- Chart Plotter bearings (when moving)
- Auto-helm compass
- Binocular compass
- OpenCPN GPS Bearings

So what is the value these days of professional swinging of the ships compass?

Thanks,
Steve

The ship's compass is normally the only compass direction information sourced totally Within the boat. If you have a magnetic compass in your binoculars that would count, but it is usually less accurate. Perhaps like trying to read the card on a little hand-held compass on a rolling boat.

The other direction sources you mention are all calculated from information from satellites (and perhaps cellular phone input) combined with their own internal firmware and software. All are subject to errors or signal dropouts and of course are under assault by the harsh marine salt environment.
I love our plotter and AP, but would not place their information "above" that of the ship's compass.
Same admiration for my laptop computer navigation application with its plugin GPS antenna.

So to me it's not a matter of it being an "only" compass direction source, but rather part of a hierarchy of information, with my ship's compass always the standard against which all other sources are compared.

More navigation input is almost always better... and never throw away your paper charts!
:)

Trivia note: we are at 45° 31' 23.0304'' N, in Portland OR
 
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GrandpaSteve

Sustaining Member
The ship's compass is normally the only compass direction information sourced totally Within the boat. If you have a magnetic compass in your binoculars that would count, but it is usually less accurate. Perhaps like trying to read the card on a little hand-held compass on a rolling boat.

The other direction sources you mention are all calculated from information from satellites (and perhaps cellular phone input) combined with their own internal firmware and software. All are subject to errors or signal dropouts and of course are under assault by the harsh marine salt environment.
I love our plotter and AP, but would not place their information "above" that of the ship's compass.
Same admiration for my laptop computer navigation application with its plugin GPS antenna.

So to me it's not a matter of it being an "only" compass direction source, but rather part of a hierarchy of information, with my ship's compass always the standard against which all other sources are compared.

More navigation input is almost always better... and never throw away your paper charts!
:)

Trivia note: we are at 45° 31' 23.0304'' N, in Portland OR

I don't disagree with any of that, but with all of those sources, I am not sure of the value of the precision swinging of the compass. Although I think I would enjoy knowing I have a precise reference for a period of time. Then again, I am sailing on the Chesapeake bay and usually am within sight of an identifiable landmark.

On a submarine we had a Sperry Gyrocompass and that got regular corrections (of course the gyrocompass does not care about magnetic deviation, totally of-topic, sorry).
 
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mfield

Member III
.. and never throw away your paper charts!

Not to too much of a pedant but:

The compass swing is a chart of the differences on a particular boat between magnetic north and what the compass reads. This is due to local interference on the boat, large chunks of iron and electronics generating magnetic fields.

An iPhone sources it's compass direction from a magnetic sensor in the phone and needs no external communication (it does not do well in salty water though)

Yes - throw away your paper charts. The magnetic deviation (difference between true north and magnetic north) it whats printed on the charts and it's that number that is changing a bit. Buy new ones, the chart changes for depth will vary more year for year than magnetic deviation.

I think the compass on a modern boat is probably more unreliable because of all the electronics stacked around the binnacle than changes in the location of magnetic north.

I hear the direction of north / south switches every 100,000 years or so - that will be fun
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
I think they just update the model to keep GPS on track. This ain't bad overview (eiven though the author has a mere BS degree):

https://www.washingtonpost.com/scie...ent-finally-caught-up/?utm_term=.bd104885fffb

Compass? It's OK, if you get the variation and deviation right. But also useless, in a way, because steering a given course is so impossible given current, leeway and a helmsman.

What matters is knowing where you are--the miracle of GPS.

I was a thousand miles off San Francisco, and my chartplotter showed a dozen or so waypoints in our wake, arching northeast from Oahu. The new course, after climbing over the North Pacific High, was to be a long dive south toward home. So I figured, there being not much else to pass the time, what if I lost all GPS?

I noted that my whisky compass, chartplotter compass and the compass on the wheel pilot had never agreed--five degrees different at least.

I got out the protractor and charted the course home. I made the usual corrections on the paper chart and drew a line. No problem, the way we all used to navigate by dead reckoning.

It was nowhere near the GPS course for Los Angeles. Huh? I plotted the course to nearer waypoints ahead, which I typically used for weather routing based on Gribs. The course to them was different, too. I began to sweat. Wait, what course was right? I think I used the iPhone compass, too--and it agreed more with the chartplotter than my chartwork.

I never did figure the differences out. I still don't know what I did wrong. I don't think the Great Circle Route issue made that much difference.

I concluded that all I really could do was head in the "right direction" and note my current position each noon. Once, that would've been a sextant sight good maybe to a mile (or five or ten or twenty). Any long view--the correct course for a target 1000 miles away--seemed unconfirmable. Of course such a "fastest" course exists. Any chartplotter will tell you, and every commercial ship follows that fuel-saving route exactly, when possible. I just couldn't plot it on my paper chart.

I'm not an expert navigator. They win races with this stuff. They solve all sorts of puzzles with skill and experience (our navigator in the Fastnet race found the Lizard in a full gale holding a hand-held RDF in a pitching cockpit when the null was 20 degrees wide).

The result of my experience was that I have zero confidence that my Globemaster compass will get me where I want to go, swung or not.

I recall Chichester approaching a dangerous passage, I think Tasmania. He took sights every hour, in and out of fog and other opaque skies and lost horizons. He was concerned less with his course than his position. And, being the great navigator Chichester was, when the passage hove into view 10 miles ahead he was exactly where he expected to be.

Man, that ain't me. Moving magnetic north or not, it was GPS that let me sleep.
 
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toddster

Curator of Broken Parts
Blogs Author
For some unknown reason, I've never found the iPhone compass to be particularly accurate or even stable for taking bearings. It does OK when in motion. It can magically apply the declination correction (or not) automatically. (According to the model data referenced in the OP.) But for example, I've tried using it to mark 90° fence corners and it's not even close. I don't understand why not and don't really trust it.

Oh, a couple more for the list:
The SeaTalk network has a fluxgate compass (usually agrees quite well with the ship's compass), but if that's turned off, the tiller pilot has its own internal compass that it uses.
More Hand bearing compasses built into the scuba rigs. (Although I see that the latest and greatest gear has gone over to electronics there, too. Even heads-up displays!)
Hiker's compass in my backpack.
They're everywhere!
 

bgary

Advanced Beginner
Blogs Author
...I am not sure of the value of the precision swinging of the compass.

I have half a toe ready to dip into this pool.

A while back - when I couldn't find anyone in the Everett area to swing my compass - I built my own table. using the GPS, pointed the boat (the direction it indicated was) True North, and noted what the compass said. Did the same at 10-degree intervals around the compass and made a sticker that fits on the aft side of the helm compass housing... XXX "true" = YYY "compass". (which means that I can - at a glance - figure out that YYY "compass" is XXX "true")

At the moment, I'm thinking that's "good enough for jazz", as Christian says. But open to other thoughts.

Bruce
 

Teranodon

Member III
I'll add my $0.02.

I consider the binnacle compass to be an ornament only. I'll glance at it from time to time, but never rely on it for navigation. It's more important to me to have my handheld VHF, binoculars, and hand bearing compass near at hand. These all interfere with the Ritchie.

I use my hand bearing "hockey puck" all the time, in conjunction with the Garmin 9-inch touch screen chartplotter. I use these both ways: to identify a landmark such as a buoy, headland or marina, or to physically locate a feature that I see on the chart. I'm not sure what Garmin uses for deviation. Maybe its programmable, I'll have to check. In any case, a couple of degrees is not going to matter. I always set the GPS to display magnetic heading and bearing of the next waypoint. I compare these numbers frequently, but I don't worry too much about their absolute accuracy.

The Raymarine autopilot has a magnetic sensor. I mounted it in the lazaretto and, every once in a while, that leads to some crazy course changes when someone parks their back pocket nearby. The controller head displays the heading continuously. It usually differs from the Ritchie by several degrees but it doesn't matter.

I don't worry about my GPS units crapping out since I carry several, from the 9-inch to a 78sc, to a couple of old etrex units, to my phone. I suppose it's possible that the Pentagon might shut the whole thing off some day, but I'll take my chances. In any case, the hockey puck plus paper charts will get me to where I want to go.

I've done some sailing in high latitudes and, there, we relied on GPS exclusively. When circumnavigating Spitsbergen on a C&C34, we reached latitude 80. The binnacle compass didn't work at all. On a 37-footer in the Northwest Passage, we were further south but closer to the magnetic pole. Same thing.
 
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toddster

Curator of Broken Parts
Blogs Author
As far as actual use... I like video-game navigation as much as the next guy, but crossing the bar in fog I find that I’ve kept my eye on the compass and only occasionally glance at the GPS display to see if I’m still in bounds. Not sure that’s the most rational solution, but it seems to define my relative levels of paranoia. Farther up-river, there is usually a landmark or beacon to watch instead of the compass.
 

Ryan L

s/v Naoma
Must be. I just don't know how to make the corrections on the paper.


There is a special chart (I think it was called a gnomomic chart?) that you can use to easily plot a great circle route. First you draw a straight line between two locations. Then you take waypoints spaced at whatever distances on the line make sense to you. Then you plot those waypoints on a "regular" chart and it appears as a great circle route.
 

Kevin A Wright

Member III
I have to admit that I use the compass very little anymore, although I do have both the binnacle and a hand held left over from the days of taking sightings to determine my position. Now I just look around me since I pretty much know by sight everything within a weeks travel in any direction. When the fog rolls in, a compass doesn't help much with the currents in the straights - GPS is vastly better. And a good paper chart when you get in close with the hard bits lurking in the shallows.

Although I will say in the old days (before GPS) we used to carry a pocket AM "transistor" radio with us when fishing in the Straights between Port Angeles and Victoria BC for when the fog rolled in. For those old enough to remember these were about twice the size of a pack of cigarettes and usually ran off a 9v battery. They had a coil antenna in the back of radio. You'd tune it to KONP or KAPY in Port Angeles and then use it as a radio direction finder to get home (keeping in mind Ediz Hook was in between you and that radio station). The signal would get louder or softer as you turned the radio peaking when the back of the thing was pointed at the station. Compared against the compass it would tell you how fast you were being thrown east or west by the tide. A compass alone would just run you aground somewhere between Sequim and Freshwater Bay. And you got to listen to golden oldies while you sailed!

Now if I was doing transpacific crossings it would be different. But here in the inland waterways, just not so much.

Kevin Wright
E35 Hydro Therapy
 
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