Question About Declination

All right. This question is for all you compass savvy travelers out there. First off, I don't have a GPS nor will I be purchasing one anytime soon. I do however have a nice Silva Ranger orienteering compass with a built in gear to permanently set the declination. Secondly, I understand the basics of compass use and would not have a problem navigating. I have used compasses to steer my way up munroes covered in thick fog in Scotland countless times.

My question is geared more towards my confusion of some explanations found in "Freedom for the Hills" 7th edition and my Silva compass manual. I will quote these explanations/instructions for your benefit. Perhaps you even have this book and model of compass yourself, which would make you even more qualified to assist me.

Now, I understand that we who live on the East coast of the U.S. or East of the line of 0 declination or "agonic line" would be described as having to use a Westerly declination. On one of my maps of N.H. it says that there is a 17degree westerly declination. For those living on the West coast, they would have an Easterly declination as magnetic north is somewhere to the East of true North. Ok, that I get, what I don't get is the following explanations.

Taken from "Freedom of the Hills" page 95 in the chapter on navigation

"In areas WEST of the line of zero declination, the magnetic needle points somewhere to the EAST (to the right) of True North. So, these areas are said to have EAST declination. It works just the opposite on the other side of the line of zero declination, where the magnetic needle points somewhere to the WEST (left) of True North, these areas have WEST declination."

Now, from the manual of my Silva Ranger compass model 515

"Turn the dial to increase or decrease that reading according to the declination. Easterly,
decrease the dial reading and westerly, increase the reading.
For example, if your bearing from the map is l00º and the declination is 10º East,
DECREASE the reading 10º by turning the dial to 90º. If the declination is 10º West,
INCREASE the reading of l00º to read 110º."

Now, on page 96 of Freedom from the hills, there are two illustrations (figure 5-10 and figure 5-11) If you have this book, you can turn and see what I mean. in f. 5-10, it shows that in Vermont (b) the needle points West of true north, just like the book says, but in Figure 5-11 (B), the compass diagram shows that the declination arrow is decreased from true north to give a reading of 345 degrees North.

Now remember form before that from my compass instructions I am to Increase when I have a Westerly declination? Shouldn't the true declination be set to 15 degrees North, NE? By subtracting, I would be increasing the distance that magnetic north differed from true north, rather than correcting the error.

Does anyone see my point. Am I wrong? If I am, what am I missing? Is N.H. true north 343 degrees or 17 degrees? Thanks if you can make heads or tails of this and sorry for such a long post.

If anything, the map I hold in my hand must be wrong if I am wrong, since it says that NH has a 17degree West declination. Meaning that, the offset between true and magnetic North is 17 degrees West. If the rhyme West is Best and East is least holds true, then I would ADD 17 degrees to my bearing or azimuth.

http://www.atlasquest.com/tutorials/...clination.html

Now, according to this site, there are two ways and one talks of converting true north to magnetic north and the other is the opposite when converting magnetic north to true north. According to that site, the above references from both Freedom of the Hills and my instruction manual would suggest that they are instructing me to convert True North to Magnetic North. It is all so very confusing as I am reading inconsistencies in those two books and then even in a "map and compass" manual written by Cliff Jacobson. If anyone here has that book I can point out the pages I am referring to.

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Stan said:

I never set the declination ... if it gets unset without me realizing it it could throw me off. I always use the math and if I get confused ... ... I remember that, in the Northeast, magnetic north is to the west (left) of true north.

Everytime I stop to think about it, however, I'm reminded of the millipede that froze in its tracks when asked how it walked.

Not to take anything away from the convenience of GPS, I much prefer map and compass, especially in the Northeast where there are so many navigational clues that the technology actually detracts from my affinity with and appreciation of the surroundings.

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Dr. Dasypodidae said:

I also never set declination, unless I am mapping something geologic. Instead, I tape a list of magnetic bearings for all the key bailout points for a particular trip on the back of my compass so that I never need to think about anything, especially if I should get cold and wet, or hypothermic.

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Neil said:

I never use a compass with "adjustable" declination because I would have to unlearn previous learning.

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prino said:

These are the reasons I like orienteering maps... they are all drawn to Magnetic North!

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Its pretty easy--you just set the local declination on the compass and then use the compass and map as if the declination was 0 deg.

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Stan said:

Who needs a compass anyway??? at least on sunny days. If the sun is shining point the hour hand towards the sun and noon will be the direction of south... while 6 is direction towards north.

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Stan said:

if you incorporate elevations and topography in fixing your location and direction of travel.

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Stan said:

... yeah, always carry a compass. Two is good practice.

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