Magnetic North Shift

[Tbrad]

Oh man I hope it's not shifting so fast that Delta can't find Seattle next Saturday! I gotta get to my boat!

[boatman61]

Originally Posted by Tbrad

Oh man I hope it's not shifting so fast that Delta can't find Seattle next Saturday! I gotta get to my boat!

Phew.... for one awful second I thought we had an ANCHOR SHIFT.....

[TheWatchman]

So based upon the rapid acceleration of shift, the recommended annual adjustment will change as I am seeing this. Looking at charts currently in my possession, how am I able to keep up?

Is there a link to NOAA or other navigational authority that gives me accurate adjustment? Maybe I dont want to purchase a complete set of charts annually.

With large amounts of solar activity being forecast, the likelyhood of continous uninterrupted gps navigation is unlikely. I would like a manual source of navigation that is reliable in close quaters

[cal40john]

Originally Posted by TheWatchman

Well, thank you ladies and gentlemen;

4 plages of blather and only five posts that address the topic.

Well to make the data in my post relate more directly to your question, at the current rate of 10 minutes per year, my charts have to be 6 years old to make the magnetic rose 1 degree off. I don't think I can hold a course that close.

[boatman61]

Chart, depth sounder, eyeballs...
also to keep upto par with magnetic compass movements do a tri-fix from known charted positions and calculate the variation from there... assuming you have you boats deviation card aleady made up for the calculations.....

[stevensuf]

its been moving 40 or so miles a year and acceleratin while teh field strenght has been weakening ,it is a sign of a magnetic reversal the north will become south and vice a versa, happened many times in the past, no ones quite sure how quickly it occurs. Some think its linked to the suns magnetic field, the sun has also been dropping on solar activity and magnetic field, leading to quite a cold spell for the future, forget global warming for the next 40 years. i wouldnt be worried about massive flares, the sun is going to be dead of sun spots for some time once the current solar cycle is over.

[Therapy]

Originally Posted by TheWatchman

So based upon the rapid acceleration of shift, the recommended annual adjustment will change as I am seeing this. Looking at charts currently in my possession, how am I able to keep up?

Is there a link to NOAA or other navigational authority that gives me accurate adjustment? Maybe I dont want to purchase a complete set of charts annually.

With large amounts of solar activity being forecast, the likelyhood of continous uninterrupted gps navigation is unlikely. I would like a manual source of navigation that is reliable in close quaters

Could it be that with no GPS and the pole wobbling to and fro that it would not be possible?

[osirissail]

Originally Posted by TheWatchman

. . .
Is there a link to NOAA or other navigational authority that gives me accurate adjustment? Maybe I dont want to purchase a complete set of charts annually. . . . .

Why on earth/seas would you want to buy new charts? - Nautical charts are made and laid out based on True North and not Magnetic North. That little compass rose circle on the chart is used to conveniently convert True to Magnetic and it normally contains the annual variation shift.
- - Same with GPS, you can select True instead of Magnetic in the menu and all headings, etc. will be in relation to True North and not be affected by Variation.

[jackdale]

Originally Posted by osirissail

Why on earth/seas would you want to buy new charts? - Nautical charts are made and laid out based on True North and not Magnetic North. That little compass rose circle on the chart is used to conveniently convert True to Magnetic and it normally contains the annual variation shift.
- - Same with GPS, you can select True instead of Magnetic in the menu and all headings, etc. will be in relation to True North and not be affected by Variation.

Yes indeed. That is why we almost always work in True. The purists always work in true.

The centre of the compass rose is outdated within a year of publication.

[TheWatchman]

OK,
Exactly the point I am making. To make a course, one looks at the charts and corrects for magnetic north so one can navigate using a compass bearing in the cockpit.

How much correction is now a question because the standard deviation is changing from previous standards as listed on said charts.

Am I crazy or maybe a navigational dinosaur? If I choose to forgo electronic navigation as a result of choice or lack of signal, for whatever reason, I am left with celestial and dead-reckoning. These are dependant on compass verification. If I dont know what the compass is telling me, because the deviation is different than it used to be, because of changing or accelerating deviation, what is the solution?

[Therapy]

I guess on a 53 foot ketch you could keep a pretty close course but on all the smaller boats I have been on even a couple of degrees would not have made much difference.

But then I am not crossing oceans.

[jackdale]

Originally Posted by TheWatchman

OK,
Exactly the point I am making. To make a course, one looks at the charts and corrects for magnetic north so one can navigate using a compass bearing in the cockpit.

How much correction is now a question because the standard deviation is changing from previous standards as listed on said charts.

Am I crazy or maybe a navigational dinosaur? If I choose to forgo electronic navigation as a result of choice or lack of signal, for whatever reason, I am left with celestial and dead-reckoning. These are dependant on compass verification. If I dont know what the compass is telling me, because the deviation is different than it used to be, because of changing or accelerating deviation, what is the solution?

There are two processes; correcting (compass +/- deviation=magnetic+/-variation= true add easterly corrections) and uncorrecting (true+/-variation=magnetic+/-deviation=compass add westerly correcting)

Variation is calculated using the compass rose



In this case the current variation is

4.25Degrees - 8 X 26/60 = 4.25-3.5=.75 degree

Deviation is from a deviation table specific to the boat and changes according to heading.



My manual has a whole chapter on this, but I will not post it.

[TheWatchman]

Which manual are you referring to?

As I have noted, and you point out, the chart states annual deviation of 5 degrees or as you wrote in this case 4 degrees.

Yet, the news states we are now accelerating to 10 degrees.

5 degrees is a lot of difference to me and if the rate increases?

So my question is how to validate appropriate deviation?

[cal40john]

Originally Posted by jackdale

Yes indeed. That is why we almost always work in True. The purists always work in true.

The centre of the compass rose is outdated within a year of publication.

Do you mean the magnetic rose is far enough off in one year that you can see errors in your navigation? What are you doing that 10 minutes of error in the PNW show up?

Originally Posted by TheWatchman

OK,
Exactly the point I am making. To make a course, one looks at the charts and corrects for magnetic north so one can navigate using a compass bearing in the cockpit.

How much correction is now a question because the standard deviation is changing from previous standards as listed on said charts.

Am I crazy or maybe a navigational dinosaur? If I choose to forgo electronic navigation as a result of choice or lack of signal, for whatever reason, I am left with celestial and dead-reckoning. These are dependant on compass verification. If I dont know what the compass is telling me, because the deviation is different than it used to be, because of changing or accelerating deviation, what is the solution?

If you're that worried get on the NOAA website once a year to find the current variation and don't use the magnetic rose. If you don't want to use a computer I'm sure NOAA has publications out every year to update the variation.

Compute variation or view current years variation map:
Magnetic Declination (Variation) Home

Accuracy of their model:
World Magnetic Model - Model Limitations


What kind of accuracy are you guys shooting for? When I took the celestial nav course from the NROTC folks on campus years ago I had to use two right triangles to get the accuracy needed to get good grades, the parallel rules aren't parallel enough for that kind of accuracy. I've never used anything but parallel rules outside of class, always managed to figure out where I was close enough.

John

John

[jackdale]

Originally Posted by TheWatchman

Which manual are you referring to?

As I have noted, and you point out, the chart states annual deviation of 5 degrees or as you wrote in this case 4 degrees.

Yet, the news states we are now accelerating to 10 degrees.

5 degrees is a lot of difference to me and if the rate increases?

So my question is how to validate appropriate deviation?

Sorry I wrote the manual that I use to teach navigation.

Deviation is from a deviation card specific to the boat. It is not on the chart; variation is.

What news. Variation is not increasing or decreasing 10 degree, unless you are very near the magnetic pole.

We currently have 18 degrees East variation in the area in which I sail. It is changing 8 minutes west each year, i.e. decreasing.

I am unsure of your last question. A GPS has algorithms that can account for variation.