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True North


BigFurryMonster
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Your GPS uses true north which can be quite a ways off from magnetic north depending on your location.

 

As far having to be moving to get a good reading, that all depends on what GPS you have. I use a Garmin E-Trex Vista which will continue to point to true north whether Im moving or standing still.

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You can get a magnetic compass that may be set to point to True north at your better outdoors recreation stores, Your higher end models from Silva and Suunto (Silva is made by Sunnto) will have adjustable declination and most all compasses from Brunton will have Adjustable decliation. You can look up how much of an adjustment you will have to make on a USGS Topo map, there will be a marking along the bottom of the map that shows the declination for that area. With any luck someone in the shop were you buy the compass will be able to help you the setting.

 

As far as a compass in a GPS, with most GPSr you must be moving for the compass to work.

 

If the GPS has a magnetic style of compass, Garmin Vista, and a few other Garmins as well as the Magellan Sport track color and Meridian Platinum. The compasses in these will work while stationary, the Garmins must be held level for an accurate reading while the Magellan do not have to be held level.

 

My choice is a std baseplate compass.

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Some caches instruct to work with the 'True North' somewhere along the way.

My old-fashioned compass points to the Magnetic North. I believe my GPS' compass does, too (not sure though).

You can use the form on this page to determine the amount of magnetic declination in your area.

 

I notice from your cache finds that you're in the Netherlands. Using the cache you found yesterday as a reference, it appears that your area is at about 4 degrees declination. That's really not enough for you to notice too significant of a variance between magnetic north and true north.

 

There are a lot of benefits to carrying a compass with you while you're geocaching (especially if your GPS does not have an electronic compass). In areas of more extreme declination you would want to make sure that your GPS was set for magnetic north just to make sure your arrows are pointing the same direction.

 

Bret

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You can look up how much of an adjustment you will have to make on a USGS Topo map, there will be a marking along the bottom of the map that shows the declination for that area. .

The declination arrow on the lower left of your map is for the declination when the map was made and does not reflect the current declination.

 

Current declination can be obtained here. Learning how to adjust from a field bearing (magnetic) to a map bearing (true) is not all that difficult to learn.

 

And here is a nice little tutorial for your use.

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Indeed, I am in the Netherlands. I get for my magnetic declination:

 

Declination = 0° 23' W changing by 0° 7' E/year

 

(using Cy's link and 52 N and 6 E in Nov 2004)

 

So the magnetic north is only 23 circle-minutes west of the true north? That's not much, and I wonder why some caches in my area specifically state that I should use True North.

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The change is very sleight, and for most people it is not going to make for much of a difference, For geocaching purposes in which the distance that is going to be covered is very short the difference in declination is not going to be noticed, using a USGS map for your declination is all that anyone will need for geocaching purposes.

 

Caches I have seen that require a compass heading have offer magnetic and true north reading so the cacher has the option, To only offer true north on a cache page is very short sighted considering not all cachers have a compass with Adj. declination.

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Interesting... Check out the map on this page.

It shows that there is (was) a line somewhere over the USA with 0 declination. Being in the Netherlands, I would expect a pretty big declination. I read somewhere that the Magnetic North is somewhere in Northern Canada, which checks out with the map but not with the declination I got.

 

For 1 Jul 1985 (the year for which the map was made), I get a declination of only 2° 38' W for a location near me (52 N 6 E) from this page

 

Of course, the red line from the map goes all around the earth, but I don't think Europe is quite on the opposite side from the USA. Not geographically speaking, anyway :anibad:

 

What am I doing wrong here?

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A) Anyone have an answer to my question above? I'm thinking of doing a cache which states I should be using True North, but I'm still not too sure I can get this right.

 

B) And if my GPS displays True North, how come it knows where this is when there is no satellite reception?

 

C) Cy -- I am not able to reproduce the declination you got. I enter the (approximate) coordinates of my house: N 52º 5' and W -4º -41', and I get a declination of 0º 58' W.

 

D) "a declination of 0º 58' W." - does this mean almost one circle-degree, or some other unit?

Edited by BigFurryMonster
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A) Anyone have an answer to my question above? I'm thinking of doing a cache which states I should be using True North, but I'm still not too sure I can get this right.

 

:( And if my GPS displays True North, how come it knows where this is when there is no satellite reception?

A) Check your GPS settings. You should be able to set it for True North or Magnetic North. Once you set it then don't worry about figuring the declination as your GPS will automatically figure it. Since it knows your lat/long and the day it will automatically calculate the declination for your exactly location.

Whether to keep your GPS set on True or Magnetic is sometimes a debate amongst people.

When you're using paper map and compass the declination can be very important, and more so depending on where you are located. In my part of the US the declination is quite small. However, if you were in Alaska it could be off by 20* or more. In some other parts of the world it would substantially more. If you were close to the North Pole you could have a declination as much as 180* which means your compass would show you going south but you would really be heading true north. As others have said the declination will be indicated on the map. You can then adjust your compass indicator for the declination.

 

:) If you're not receiving sats then it won't know where it's at whether true north or magnetic. It will show its last reading. Remember, that's how GPS work. It has to get the signals from sats.

 

(Don't know why B is showing up as a smiley.)

Edited by Wadcutter
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(Don't know why B is showing up as a smiley.)

Because the parenthesis after the capital B ) signals the forum software you want a smiley. While composing a message click on the smiley with sunglasses :( in the box on the left of the screen and see what it puts in your message.

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(Don't know why B is showing up as a smiley.)

Because the parenthesis after the capital B ) signals the forum software you want a smiley. While composing a message click on the smiley with sunglasses B) in the box on the left of the screen and see what it puts in your message.

. . . and yet BigFurryMonster seems to have tricked the forum software into letting him/her write B).

 

Trick: Uncheck "Enable emoticons"

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I only succeeded after unchecking that, I confess :-)

 

Thanks for your answer, Wadcutter! I didn't realize the GPS actually calculates the difference between True and Magnetic North dynamically (i.e. depending on location and time).

I'll check my GPS-r for those settings.

 

Can anyone help with questions C) and D) ?

Edited by BigFurryMonster
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That's because CYBret got tripped up by that goofball calculator, which goes against convention by calling West longitude positive and then persisting in displaying East as negative West in the result.

Whoops...I thought that looked funky at the time.

 

Oh well...at least I know how to hold an eTrex. :(

 

Bret

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If you are dropped into an unknown location, use your GPSr to show you the declination of your area. If you have a Garmin, it should show you when you set your north reference. (The magnetic setting will show the declination.) If you have a Magellan, set a goto a local waypoint, and then read the bearing after changing the setting to true and magnetic. The difference is the declination and if the magnetic bearing is larger, the declination is east.

 

Take your compass and if it has a declination adjustment, set it and read the azimuth scale as true. If your compass does not have an adjustment, put a mark at the declination, line up the compass needle over the mark, and read true. (This pertains to most of the flat clear compasses.)

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Ladies and gentlemen,

 

The concepts presented thus far in this thread are correct. However, the use of the term declination is incorrect. This is not uncommon. Unfortunately, those of you who think that I am incorrect, and will instantly turn to google to find proof that I am in error, will indeed be able to find a plethora of web sites and publications which also use this term incorrectly. Sadly enough, some mapping companies are even in error due to the dumbing down of the science of navigation over the past 91 years or so.

 

Declination is the angular difference between where the needle of your manual compass points (or INS stabilized gyro etc), and where the MAGNETIC pole is located - not the true, or geographic pole as has been stated in this thread. Declination varies between each individual compass - think of it as calibrating your manual magnetic compass or gyro.

 

What you have all been calling declination is properly termed variance: the angular difference between true and magnetic north. This quantity varies with time and location on the planet.

 

It seems that one of the only groups of people left today who not only know and understand, but also use and rely upon, the difference are Sailors (military and civilian) and Marines (I do not know the Army or Air Force curriculums). Most people who use maps, compasses, and GPS for hiking and geocaching etc are not concerned with, and rightly so do not need, the degree of accuracy that declination calculations provide. Simply trusting that their magnetic compass is pointing close enough to magnetic north and only applying variance corrections gets them where they need to go. But to a seagoing captain, the error between where his compass (or INS stabilized gyro) is pointing and where magnetic north really is can sometimes mean the difference between running aground or not.

 

Semper Fidelis,

Culprit99

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However, the use of the term declination is incorrect.

What you say is correct. Also as you say declination has been used to describe it for so long it's become common usage. So if someone goes into WallyWorld and buys a compass, most likely the instructions will talk of declination. Not correct exactly but declination has come to what it means.

BTW, the Army and USAF also use variance, or did when I was in. And we didn't have to worry about running a ship aground either. Couldn't get me on a ship. They float in a shark's bath tub and I didn't join the military to be breakfast for a fish. :(

Edited by Wadcutter
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Some caches instruct to work with the 'True North' somewhere along the way.

My old-fashioned compass points to the Magnetic North. I believe my GPS' compass does, too (not sure though).

 

How do I find True North? Do I need to calculate the angle between Magnetic North and True North? Doesn't that change over time (a bit)?

I have found that I like to use gps for true north readings. I leave my compass turned off unless I need it. When I do turn my compass on (manually) ,it is important to remember that this is a MAGNETTIC reading. Using a compass is a good skill to have. I recommend occasional practice with them.

At least I know that U or I can walk in a straight line using one even if our gps craps out for some reason!

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Interesting thread! Change is a certainty in language and methods... The word "let" use to mean hinder in the 1600's... the term "variation" is also evolving into other terminology. I have an old pathfinding book by Robert S. Owendoff (does the name ring a bell?) and an old Orienteering handbook that use the term "Variance". I can also remember using it in a ROTC map course in the late 1960's. I've got an Army FM 21-26 "Map Reading and Land Navigation" manual dated 1987 in front of me and the term "variance" is not used. They use declination, Grid Convergence, Conversion, True North, Magnetic North, and Grid North for terms. It Looks like the horseless carriage is here to stay and we will just have to use the current terminology that is taking over.

 

Another point I'd like to bring up is that a lot of manuals ovoid complicated detail and simplify navigation methods and terms. For example it's an erroneous idea that a compass needle points to the North Magnetic Pole. If it did our Isogonic Charts would be vastly simplified. The needle responds to the earth's magnetic lines of force in the immediate area. It doesn't point to any particular place and is never more than 13 degrees off from the direction of the N. Magnetic Pole. "local disturbances" due to magnetic material in the earth's crust can also affect the magnetic lines of force in varying amounts and are not shown on the isogonic charts. It's usually less than a quarter of a degree here in the US unless you live in Arkansas or Colorado where it can be more. Ok, getting back to my point... todays manuals for the layman may not be politically correct but use the KISS method of instruction that works just fine for Joe cacher on his one mile hike in the woods.

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Ladies and gentlemen,

 

. . the use of the term declination is incorrect.  . . . 

Hmm . . ., well . .

 

By ruling out “the Internet” you've preempted the easiest way of disagreeing with what you said.

 

It is, in fact, correct to call the angle between magnetic north and true north the declination.

 

All information on the Internet is not bogus, so in spite of your statement I'll show that you're wrong about this use of “declination” being incorrect. And, I will do so using the scornful Internet.

 

Reference 1:

 

United States Geological Survey (USGS) http://geomag.usgs.gov/intro.html

 

Quotes:

 

“. . not only does the direction of the compass needle deviate from true north, but the amount of the deviation, the declination, varies as a function of geographic location; . . .”

 

“. . declination, the angle between the horizontal component of the magnetic-field vector relative to true north. . “

 

Reference 2:

 

Quote:

 

The National Oceanic and Atmospheric Administration (NOAA) -- FAQ

 

http://www.ngdc.noaa.gov/seg/geomag/faqgeom.shtml#q2

 

“Magnetic declination is the angle between magnetic north and true north.”

 

Reference 3:

 

http://home.att.net/~agligani/navigation/magnetic.htm

 

Quote:

“Some things to remember:

• Another name for variation is declination.”

 

Reference 4:

 

Quote:

 

http://southseas.nla.gov.au/biogs/P000022b.htm

 

“In the eighteenth century, the angle between magnetic north and true north was recorded in logs and journals as ‘the variation’. Today, the scientific name for this ‘variation’ is magnetic declination.”

 

============

 

I’ve now produced two very authoritative sources and two more sources that say you're mistaken.

 

At this point it becomes your obligation to produce a couple of sources (other than unsupported statements and opinion) that say specifically this use of declination is wrong/incorrect.

 

To be clear, I'm not saying the use of variation is incorrect, just that the use of deviation is correct. In fact, the use of variation is obsolete, but that's not what I’m arguing with this post.

 

Edited to add:

 

Reverence 5:

 

The Smithsonian Museum

 

http://americanhistory2.si.edu/surveying/o...rdnumber=997351

 

Re: Surveyor's Vernier Compass

 

"A pinion with capstan head, located outside the box at W and marked "Declination," is used to offset the compass for magnetic variation."

Edited by Thot
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If I'm not mistaken, the red and white pole would be moving all the time as it's on an ice flow. There's no land up there. Only the Antartica which is land where the south pole is located would the white and red pole stay still. (OK except for continental drift but we'll all be dead before anyone would notice it moved.)

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If I'm not mistaken, the red and white pole would be moving all the time as it's on an ice flow.  There's no land up there.  Only the Antartica which is land where the south pole is located would the white and red pole stay still.  (OK except for continental drift but we'll all be dead before anyone would notice it moved.)

 

It's in the front yard of the house where this old fat dude wears a red suit all the time. His wife is pretty cool, though -- she is always baking cookies. There's a bunch of short dudes in green suits always running around busy making toys and stuff.

 

The reindeer are cool to look at. One of them has a big red shiny nose.

 

I saw a couple of long lists of names inside his house. One list was labeled 'Good' and the other 'Bad'. My name was on the top of the 'Bad' list in big bold letters. I wonder what that is all about?

 

:(

Edited by dsandbro
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If I'm not mistaken, the red and white pole would be moving all the time as it's on an ice flow. There's no land up there. Only the Antartica which is land where the south pole is located would the white and red pole stay still. (OK except for continental drift but we'll all be dead before anyone would notice it moved.)

No, no. It's always in the same place. Since we imagine it, we always imagine it at exactly true north.

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Now that is just ridiculous. Why would there be a barber at the north pole? Penguins don't need a haircut.

Stop! Stop! This is getting silly! There are no penguins at the North Pole!

 

(except maybe the pet penguin kept by the fat guy in the red suit)

 

 

This reminds me of:

("We have everything under control. There are no penguins at the North Pole!")

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Now that is just ridiculous.  Why would there be a barber at the north pole?  Penguins don't need a haircut.

Stop! Stop! This is getting silly! There are no penguins at the North Pole!

 

(except maybe the pet penguin kept by the fat guy in the red suit)

 

Did they use penguin repellent up there? You know how they are. Once you get one you end up with a bunch of them. I use penguin repellent around my house and it works. Haven't seen a penguin within miles of the place.

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