Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 07-03-2011, 15:11   #61
Registered User
 
Tbrad's Avatar

Join Date: Dec 2010
Location: Englewood, Ohio/Oak Harbor, Wa
Boat: catalina 27 & Windrose 20 Hunter 34
Posts: 202
Re: Magnetic North Shift

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

__________________
Tbrad is offline   Reply With Quote
Old 07-03-2011, 15:22   #62
Freelance Delivery Skipper..
 
boatman61's Avatar

Community Sponsor
Cruisers Forum Supporter

Join Date: Jan 2010
Location: PORTUGAL
Posts: 20,226
Images: 2
pirate Re: Magnetic North Shift

Quote:
Originally Posted by Tbrad View Post
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.....
__________________


Born To Be Wild
boatman61 is online now   Reply With Quote
Old 07-03-2011, 15:23   #63
Registered User
 
TheWatchman's Avatar

Join Date: Feb 2011
Location: Channel Islands, CA
Boat: Spencer 53 Ketch
Posts: 42
Images: 2
Re: Magnetic North Shift

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
__________________
TheWatchman is offline   Reply With Quote
Old 07-03-2011, 15:29   #64
Senior Cruiser

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Seattle
Boat: Cal 40
Posts: 2,401
Images: 7
Re: Magnetic North Shift

Quote:
Originally Posted by TheWatchman View Post
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.
__________________
cal40john is offline   Reply With Quote
Old 07-03-2011, 15:32   #65
Freelance Delivery Skipper..
 
boatman61's Avatar

Community Sponsor
Cruisers Forum Supporter

Join Date: Jan 2010
Location: PORTUGAL
Posts: 20,226
Images: 2
pirate Re: Magnetic North Shift

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.....
__________________


Born To Be Wild
boatman61 is online now   Reply With Quote
Old 07-03-2011, 15:32   #66
Registered User
 
stevensuf's Avatar

Join Date: Dec 2010
Location: Back in Scotland!
Boat: Gib sea 43
Posts: 840
Images: 10
Re: Magnetic North Shift

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.
__________________
stevensuf is offline   Reply With Quote
Old 07-03-2011, 16:06   #67
Senior Cruiser
 
Therapy's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: W Florida
Boat: The Jon boat still, plus a 2007 SeaCat.
Posts: 6,894
Images: 4
Re: Magnetic North Shift

Quote:
Originally Posted by TheWatchman View Post
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?
__________________
Therapy is offline   Reply With Quote
Old 07-03-2011, 16:19   #68
Senior Cruiser
 
osirissail's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: A real life Zombie from FL
Boat: Gulfstar 53 - Osiris
Posts: 5,416
Images: 2
Re: Magnetic North Shift

Quote:
Originally Posted by TheWatchman View Post
. . .
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.
__________________
osirissail is offline   Reply With Quote
Old 07-03-2011, 16:24   #69
Senior Cruiser
 
jackdale's Avatar

Cruisers Forum Supporter

Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 5,048
Images: 1
Re: Magnetic North Shift

Quote:
Originally Posted by osirissail View Post
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.
__________________
ISPA Yachtmaster Ocean Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203,204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)
jackdale is offline   Reply With Quote
Old 07-03-2011, 16:39   #70
Registered User
 
TheWatchman's Avatar

Join Date: Feb 2011
Location: Channel Islands, CA
Boat: Spencer 53 Ketch
Posts: 42
Images: 2
Re: Magnetic North Shift

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?
__________________
TheWatchman is offline   Reply With Quote
Old 07-03-2011, 16:48   #71
Senior Cruiser
 
Therapy's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: W Florida
Boat: The Jon boat still, plus a 2007 SeaCat.
Posts: 6,894
Images: 4
Re: Magnetic North Shift

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.
__________________
Therapy is offline   Reply With Quote
Old 07-03-2011, 16:53   #72
Senior Cruiser
 
jackdale's Avatar

Cruisers Forum Supporter

Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 5,048
Images: 1
Re: Magnetic North Shift

Quote:
Originally Posted by TheWatchman View Post
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.
__________________
ISPA Yachtmaster Ocean Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203,204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)
jackdale is offline   Reply With Quote
Old 07-03-2011, 17:06   #73
Registered User
 
TheWatchman's Avatar

Join Date: Feb 2011
Location: Channel Islands, CA
Boat: Spencer 53 Ketch
Posts: 42
Images: 2
Re: Magnetic North Shift

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?
__________________
TheWatchman is offline   Reply With Quote
Old 07-03-2011, 17:08   #74
Senior Cruiser

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Seattle
Boat: Cal 40
Posts: 2,401
Images: 7
Re: Magnetic North Shift

Quote:
Originally Posted by jackdale View Post
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?

Quote:
Originally Posted by TheWatchman View Post
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
__________________
cal40john is offline   Reply With Quote
Old 07-03-2011, 17:15   #75
Senior Cruiser
 
jackdale's Avatar

Cruisers Forum Supporter

Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 5,048
Images: 1
Re: Magnetic North Shift

Quote:
Originally Posted by TheWatchman View Post
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.
__________________

__________________
ISPA Yachtmaster Ocean Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203,204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)
jackdale is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Where to Buy Throttle and Shift Lever ? Garrett Engines and Propulsion Systems 5 14-05-2010 05:12
Stuck Shift Lever Eddie Engines and Propulsion Systems 5 29-03-2010 07:15
Stiff Gear shift mayphoto Propellers & Drive Systems 4 14-08-2008 20:48
Magnetic Induction Cooktops Lodesman Provisioning: Food & Drink 15 11-03-2007 20:26



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 10:26.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.