Learning my new Garmin 76

[Paul D.]

I will second that the first thing asked by athorities, in our case, Canadian RCMP, is a lat/long position. In an assist or rescue situation, the helicopter pilots punch that into their GPS and off they go.

Though I have learned both methods, I too chart and pilot in magnetic and label it so. However, here on western Lake Superior, our magnetic variation is quite small but getting larger each year.

I have a question for you compass junkies. I have heard many land-based navigators for long wilderness canoe or backpacking trips use the term "declination" instead of what we know as variation. Is that commonly known or there a difference between land and sea?

Paul - frozen up in the north country

[Bill Cochrane]

Declination and Variation are the same. Variation appears more often in navigation contexts; why the two terms and the derivation of each, I'm not sure.

[Jim Davis]

Declination:
This is the term preferred by those who study the magnetic field; it is also the term most commonly used by land navigators. Sometimes the term "magnetic declination" is used.
Variation:
This term is preferred by mariners and pilots because the word "declination" also has an astronomical usage - the angle of a star or planet above the celestial equator. However, the word "variation" is used by geomagneticians to refer to time changes in the magnetic field.

[tartansailor]

Teaches declination from TRUE in aiming our guns.
As a matter of fact there is even a correction for the rotation of the earth under the projectile in flight.
But there is no correction except social ostracism for middies that don't follow accepted norms of behavior.

Dick

[Sandy D.]

Dick,
You posted "when one embarks on an extended cruise,it is certain that deviation will change".

Can you explain this for me? Is my deviation chart for my boat not accurate,say,on the east coast?

Thanks
-Sandy

[Bob Luby]

Compass
Variation
Magnetic
Deviation
True

Or only in Florida, Chicago, etc.
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STAR CRAFT REPLAYS
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Bmw M54 History

[tartansailor]

Sandy, I sent you a private bmail
Dick

[John Vigor]

When one embarks on an extended cruise, it is certain that deviation will change and if the cruise is of any distance, variation could easily change also.
See thats how mistakes occur.

OK, so I'm an old sea dog from a bygone era, but if you are in a bad situation, and the Coast Guard checks your log, following the above directive will save you much embarrassment.

Dick

Dick: I learn something every day. I would have thought just the opposite. I would have thought that variation wouldl definitely change on a long cruise, and that deviation could change also.

What is it that makes an old seadog like you think deviation is certain to change?

Cheers,

John V.
_________________

From Vigor's Rules for Life:
19. Todd's Second Principle: "No matter what they're talking about, they're talking about money."

[Neil Gordon]

What is it that makes an old seadog like you think deviation is certain to change?

It's as you consume beer that's packaged in modern aluminum cans and replace with third world, old fashioned steel cans. Be careful what you store directly behind the compass.

Seriously, it's a fair point to suggest that deviation might change as stores, spares and the like are added and/or consumed. Prudent seamanship would suggest periodic confirmation that the table in use is still valid.

[tartansailor]

The questions raised reinforce the notion that I need to be more precise in my statements. Thanks John for pointing this out, and thanks Neil for coming to my defense.
What I meant was that deviation on one heading could be much different than on a different heading.

Cheers

Dick