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So - you get a powered compass, with a GPS, that points North – for 120 bucks

No electricity – no pointy

Last year, I got four “traditional” compasses from China – for about 3 quid, delivered – granted, you have to be careful to get an accurate North, but it’s still $120 cheaper …..
 

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Does the Marlin display magnetic or true north? Being satellite based it is likely displays "true" north but knowledge of magnetic north is helpful because some data bases like aeronautical and marine charts indicate magnetic bearings. declination 1.png
Conventional compass uses need to compensate for declination depending on where you are on the planet declination.jpg

Don't forget that with the traveling magnetic pole declination changes yearly. Does the Marlin compensate for this too if one wishes to know current magnetic bearings? declination 2.jpg
 

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"Declination" refers to altitude above the horizon, ie., the angle north or south of the equator.
The word you are looking for to describe the east or west magnetic pointing of the compass relative to True North (geometric north) is "Variation".
The amount Magnetic North differs from True North is the Variation and it depends where on the planet you are and it may change year to year based on the magnetic north pole changing its position slightly year to year.
 

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Sorry mrlmd, we must come from different disciplines for I have been taught, have taught, and regularly compensate for what is overwhelmingly referred to as magnetic declination for over the last 40 years in the various surveying and engineering activities in which I have been involved . Always hated the math entailed in determining local declination via late night observations of the North Star Polaris. Never tried it with the Southern Cross but that would really hurt my brain.
While sometimes referred to as "variation" by geophysicists and others the term "declination" is the typical term I encounter and use used in the data bases I have dealt with from USGS, NOAA, property records, legal descriptions, court documents, county records, etc.
Both terms are valid expressions for the permutations in the earth's magnetic field which very over time and location.
 

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Sorry mrlmd, we must come from different disciplines for I have been taught, have taught, and regularly compensate for what is overwhelmingly referred to as magnetic declination for over the last 40 years in the various surveying and engineering activities in which I have been involved . Always hated the math entailed in determining local declination via late night observations of the North Star Polaris. Never tried it with the Southern Cross but that would really hurt my brain.
While sometimes referred to as "variation" by geophysicists and others the term "declination" is the typical term I encounter and use used in the data bases I have dealt with from USGS, NOAA, property records, legal descriptions, court documents, county records, etc.
Both terms are valid expressions for the permutations in the earth's magnetic field which very over time and location.
In 27 years in the military I've always been taught the term was True North to Magnetic North Declination as well. Heck, even the Forest Service Maps call it this (look at bottom of Map). Maybe there are other terms which mean the same thing.
 

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Compass bearing = true bearing +/- magnetic variation/declination +/- compass deviation

Not all compasses are the same (just to add to the confusion)

“North” is best described as “probably somewhere over there” …… ;)
 

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“North” is best described as “probably somewhere over there” …… ;)


Love it, use it. Usually, by waving my hand and arm in a back and forth manner giving plenty of error on either side of the "perceived northerly direction". Sometimes I can see the sun and that helps me point more north than I was originally thinking. :p
 

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I don't want to start a war on here, but every navigational or nautical reference as well as every published government nautical chart has a compass rose with VARIATION on it. All the government publications for planetary or star sightings used for celestial navigation or observation and location, ie., with a sextant or any other instrument, refer to the star's height above the horizon as its' DECLINATION, also called altitude.
Look up the definition of these words in a dictionary or do a Google search if you don't believe me.
I find it hard to believe that there would be interchangeability between these two words in trying to describe such a precise mathematical measurement. It would make it very confusing to discuss any of this as they have 2 different meanings in 2 different disciplines. That's like how the NYPD can't communicate with the NYFD because they are on 2 different radio frequencies and can't talk to each other.
 

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I don't want to start a war on here, but every navigational or nautical reference as well as every published government nautical chart has a compass rose with VARIATION on it.
Hell - it beats another oil thread ..... :D
 

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Both declination and variation have multiple meanings in various disciplines. Neither term has an exclusive application.
However to imply that declination is not a valid term for the numerical value of the difference between true and magnetic north is an absolutely incorrect assertion as far as common usage in the United State.. They are synonyms in regards to describing deviation of magnetic north from true north.
If you do not wish to believe someone who has extensive surveying and cartographic experience I would suggest you simply look at any USGS 7.5 minute quadrangle maps or 2 degree sheets to see that the term DECLINATION is a commonly used term in government publicized maps. My extensive library show a consistent reporting of magnetic deviation from true north as DECLINATION. As a matter of fact I have just searched a dozen or so of my USGS maps in order to substantiate and double check the facts before responding. Indeed all their compass roses indicate the declination value at center of the map as opposed to variation.

I have not stated, nor am not saying, that variation is not also an appropriate term. Do not be confused and think I attempting refute any claim as to the validity of Variation.

However I am well prepared and fully willing to go to war over any continued assertion that declination is not a correct term. Does anyone think I made up or falsified the graphics and associated labeling in my post #3?
Shall we escalate the war? I am very ready with significant substantiation.
Still insist declination is not an appropriate term?
See Admiral's post #7 for an example of the commonly encountered publicized USGS compass rose format.
 

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I also have extensive nautical experience as you have with terrestrial experience and the term on the water for the difference in True North and Magnetic North is Variation. To be absolutely correct, if you want to apply your term to the difference between True North and Magnetic North, the correct term is "Magnetic Declination". "Declination" by itself is the term for the angle, or the altitude, above the celestial horizon for a celestial body. There's no need like I said to start a war here, these camps are speaking 2 different languages which makes it all harder to communicate properly.
And obviously, the USGS cartographers and the NOAA chartmakers and astronomers should get on the same page.
And you know what? - USGS is wrong. Ha.
 

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And obviously, the USGS cartographers and the NOAA chartmakers and astronomers should get on the same page.
And you know what? - USGS is wrong. Ha.
So mrlmd are you saying NOAA would be the more accurate entity to use here; or another agency? I have no skills in this activity.
 

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Forgive me for using commonly accepted applicable terrestrial terminology, that is what I learned in my cartography coursework at university. There we got to play with all sorts of fun stuff like enormous room filling ex-Nazi Lietz stereoplotters that were war reparations,( loot, booty, plunder?) from back when "to the winner go the spoils".
Anyways it was only an attempt to elaborate on what I assumed was a terrestrial application, ie I thought syberness intended to mount a Marlin's Quest Compass in Talon Motorcycle Handlebar Mount - Satellite Driven on a motorcycle instead of an aircraft or vessel . Still I don't believe the word relevant to this post that "I was looking for should have been variation" as you suggested, thus all my responses. However I guess it really doesn't matter much since the Marlin is satellite based .
I've always referred to data sources listing "Declination" when re-calibrating my trusty Brunton Pocket Transit as it has accompanied me around North America and elsewhere.
Borneo has that old Brunton now. I should have told him it's Roy Gfeller leather case is likely a collector's item now and to not let the dog chew it up. Case is possibly worth more than the instrument itself. Roy had put a finger and drain hole in the bottom of mine since I tend to fall down in the water a lot.:rolleyes:
Anyways Borneo is a heck of a globe trotter ; maybe he tell us what terminology he prefers.
Peace.
 

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Do you have any pics of that? I would love to see it and it probably works as good as new, just like an old sextant.

And to get back to the OP and the original point of this thread - A GPS compass has to be moving to determine a direction, if sitting still it has no reference points to see where it is pointing. It does not rely on the magnetic North pole like a magnetic compass does, it's using satellite positions for all its' calculations. The display for many of these can be changed to either True or Magnetic so you have to be aware of what you are looking at. They are not involved with deviation (another topic for discussion in a magnetic compass - the degree to which a compass needle is thrown "off course" by the influence of metal/magnetic structures around it) which could be a problem with a regular magnetic compass on a metal motorcycle.
Regardless of any of this, that thing is WAY TOO MUCH MONEY for what it is and what it does.
 

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Well; I got no response; so don't know if NOAA is the definitive source.

Fred's used "Magnetic Pole Declination" and mrlmd stated that the correct term is simply "Variation".

Admiral states that for his 27 years in the military; they have taught and used "Magnetic North Declination" and posted a USGS map that lists simply 2010 Declination.

And Fred states that he is not stating that "Variation" isn't a valid term also - but that "Declination" is also valid.

mrlmd then states that the correct term if using "Declination" in our context would be "Magnetic Declination" (which is what Fred first used - even adding "Pole" in the middle); but using "Declination" by itself would only refer to "the angle, or the altitude, above the celestial horizon for a celestial body". Also that the USGS is wrong and that he finds it hard to believe that there would be interchangeability between these two words.

Trying to be clear I asked if mrlmd was indicating then that NOAA was the more accurate entity - but got no response. So guessing that was what he was stating; I searched on the NOAA website.

A search for NOAA and magnetic declination came up with a page that lists: "MAGNETIC DECLINATION;
Magnetic declination, sometimes called magnetic variation, is the angle between magnetic north and true north. Declination is positive east of true north and negative when west."

You can see that Magnetic DECLINATION was used in the header. Searching NOAA and magnetic variation brings you to the same page of magnetic DECLINATION.

The site has multiple options to click on with headings such as:

Declination
Based on the World Magnetic Model (WMM) and the International Geomagnetic Reference Field Model (IGRF)
(Backup Calculators: WMM / IGRF)


Declination Map Viewer
Displays historical isogonic lines calculated for the years 1590-2015.

Magnetic Declination
By NCEI Scientist Patrick Alken

So it appears that NOAA as well as the USGS use simply DECLINATION; as well as NOAA using MAGNETIC DECLINATION and MAGNETIC VARIATION.
I would guess that since they use simply DECLINATION; that simply VARIATION would be considered valid also.

So that leaves me with the notion that both parties "word" choices are correct - and that I've spent an hour or two on the internet, but still couldn't properly find my way with a map and compass afield.

In the past; I was comparing elevation and altitude - and that was a similar can of worms. And they both ended up being based from a "specified location" somewhere on the ground (or water).
Ever heard of elevation sickness? No, but altitude sickness, yes. By people that do in fact have their feet planted firmly on the ground.
 

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Funny as hell Joe. I still am tempted to use coconut oil in my Tw engine and as you well know, it would smell yummy but not be good for the engine...so they say.
 
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