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  1. #1
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    Default Have I got this declination adjustment right?

    I've been watching some compass/map youtubes, and want to be sure I'm setting the declination correctly. The east/west part is confusing me a little.
    I'm setting my compass for the Sierras -- Lake Tahoe area, where the declination is 13 degrees east. If my understanding is correct, this means that the compass needle is pointing 13 degrees east of the North/South lines on the map. (I know, there's also grid north, but I think I can ignore that for my purpose)...
    The youtubes look like they're telling me to set the adjustment so that the red arrow (suunto orientieering compass) is to the right (east) of the north cardinal point by 13 degrees. Is this correct? Seems to me that, since I started out with the needle pointing 13 degrees too far east -- now I'm going to be 26 degrees too far east. My thinking is that I should set the pointer to the west by 13 degrees to compensate for the fact that I started out 13 degrees to the east.
    Help!? Thanks!

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    I never do the declination adjustment on a compass I just do the math, easier to me that way. get your gm angle off the map and do simple math, grid to magnetic subtract the number, magnetic to grid add the number. It seems so much easier to me then screwing with the compass declination

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    Keep it simple. The magnetic north pole is in northeastern Canada, to the east of true north if you are in the Sierras.

    You want your compass to point to true north, while your compass needle is pointing slightly east (right) of true north at magnetic north.
    So, you adjust your compass bezel (the declination) so that when the needle is pointing 13* east of true north, the compass itself is pointing at true north.

    So, ignore everything else. If declination is 13* east, you adjust your compass declination setting so the red pointy arrow thing (that you line your needle up with) is 13* east of true north. In this case, at 13* on your bezel.

    Don't read this if you are confused: If you are on Mt Katahdin, the magnetic declination is 19.5* West, so you would adjust your red point arrow thing on your compass to point 19.5 degrees left of north or adjust it to 360-19.5=340.5*. Note, Katahdin is located east of that spot in Canada where the north magnetic pole is, so when the needle is pointing to magnetic north on Katahdin, true north is slightly east (to the right) of where the needle is pointing.
    I'm not lost. I'm exploring.

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    Quote Originally Posted by nsherry61 View Post
    Don't read this if you are confused:
    Hey, if I didn't read it, I wouldn't be confused! Just kidding...
    But your directions confirm what I was seeing in the videos. I'll accept it (even tho it still seems counterintuitive to me), and hope for the best! I posted a week or so about being lost up there, so decided to bone up on my map/compass skills and head back up.
    That's interesting what you said about Katahdin being east of the magnetic pole...I thought everything over that way was west of the magnetic pole.
    (Reminds me of another interesting fun-fact ... THe most western point in the U.S. is one of the Alaskan islands!)

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    Unless you are doing serious orienteering, surveying, or nautical navigation, it is unlikely to be an issue in most places. A crude estimate will do.
    "It's fun to have fun, but you have to know how." ---Dr. Seuss

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    s suggested above, maybe instead of focusing on detailed compass navigation skills, you would be better served with building your skills with general map reading and non-compass based navigation.

    I rarely use my compass for navigation. If I do, it is rarely used for more than orienting my map when I am all turned around for some reason or another. I generally orient my map to the terrain (not to my compass), if I can see the terrain, which, you generally can in the Sierras.

    Also, it is good to remember that keeping yourself found (following your progress on your map) is much better than trying to find yourself after your are unsure of your location.

    Unless I am doing extensive off-trail navigation, I don't even take a compass with me on most hikes, other than the little button compass which I keep on my watch band and do use to keep myself oriented in areas with poor terrain visibility. I often think outdoor education focuses far to much on compass navigation skills (which are time consuming, complicated and rarely used in the field) instead of learning to really master the reading of maps and terrain, which are skills needed by everyone and vastly improve the effectiveness of compass navigation if and when it is used.
    I'm not lost. I'm exploring.

  7. #7

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    Here's a piece I posted some time ago that gives both the math subtraction and the compass-offset method for dealing with declination - maybe it will help

    http://artofwayfinding.blogspot.com/...ling-with.html

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    Quote Originally Posted by Feral Bill View Post
    Unless you are doing serious orienteering, surveying, or nautical navigation, it is unlikely to be an issue in most places. A crude estimate will do.
    Well, the difference between 260 degrees and 273 widens with distance. And, being a novice backpacker I could be wrong, but I would think that difference could potentially be really serious!

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    Quote Originally Posted by nsherry61 View Post
    s suggested above, maybe instead of focusing on detailed compass navigation skills, you would be better served with building your skills with general map reading and non-compass based navigation.
    I've heard that a lot and I know there's value to it. I want to try the compass and map on the next trip, tho, just to develop my skills in both. Because last time on this trail, I did a lot of "wandering around" off trail, since there were these big granite boulders everywhere. I've plotted the trail on the map, and, for instance, there's one piece that heads southwest from Granite Lake at a 226 degree heading (of course curving this way and that along the way), till it veers sharply to a more westerly 260 degree heading. I know, between Granite lake and the 260 heading, there are going to be granite fields -- places where I'll lose site of the trail. But I'm thinking if I can stay on my 226 degree course I should make it across the granite okay.
    And the same is true for the rest of that trail; you stay on a 260 heading till you get to a fork, then it turns sharply towards the north and a 304 heading. And all along the way, there are these granite fields where you often lose site of the trail.
    So I'm hoping that, if I can stay on my headings, I should get thru the granite and back on the trail.
    On the other hand, just looking at the map, there aren't always landmarks, that I can tell. For instance, from Granite lake to that 260 degree turn, I don't see anything. Where the 260 heading turns into the 304 heading, I do see a peak. Then the 304 will take me to the lakes.

    Quote Originally Posted by nsherry61 View Post
    learning to really master the reading of maps and terrain, which are skills needed by everyone and vastly improve the effectiveness of compass navigation if and when it is used.
    I agree strongly with this also. I really hope this experience helps me get a little better at both.

  10. #10

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    Quote Originally Posted by jefals View Post
    Well, the difference between 260 degrees and 273 widens with distance. And, being a novice backpacker I could be wrong, but I would think that difference could potentially be really serious!
    Well that depends, most case I am using a compass it I am not trying for an exact number, but more along the lines of "we need to climb that thing that is westish, as oppose to the thing that is northish"

    Sent from my SM-T110 using Tapatalk
    Love people and use things; never the reverse.

    Mt. Katahdin would be a lot quicker to climb if its darn access trail didn't start all the way down in Georgia.

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    Quote Originally Posted by JohnHuth View Post
    Here's a piece I posted some time ago that gives both the math subtraction and the compass-offset method for dealing with declination - maybe it will help

    http://artofwayfinding.blogspot.com/...ling-with.html
    Thanks. That's consistent with what I've been reading. My confusion is that, since my needle is already pointing east of true north, I'm thinking I should adjust it to the west, to compensate. And that, if I turn it to the east -- I'll just be getting myself farther away from true north.
    But everybody says I've got it wrong. And, since you teach this stuff at Harvard -- I think I'll listen!
    Thanks!

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    If I get to the point where I have to do some declination correction with a topo map, I'm probably tired &/or confused. To avoid error, I write on my topo maps what the declination adjustment formula is: East declination correction; Map Bearing = Magnetic bearing + Declination; Magnetic bearing = Map bearing - Declination. The compass I use doesn't have declination adjustment feature. I just do the math & apply it to the compass/map.
    2013 AT Thru-hike: 3/21 to 8/19
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    Quote Originally Posted by CarlZ993:2005104
    If I get to the point where I have to do some declination correction with a topo map, I'm probably tired &/or confused.
    I understand that. I've got my map and course and angles plotted ahead of time . The one thing now I wish I had -- without a GPS - is a reliable method, that doesn't rely on batteries, to know how far I've walked. Hopefully I'll know when I get to certain map landmarks, but I mean the entire way.

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    If declination is 13* east, you adjust your compass declination setting so the red pointy arrow thing (that you line your needle up with) is 13* east of true north. In this case, at 13* on your bezel.

    Yes.

    learning to really master the reading of maps and terrain, which are skills needed by everyone and vastly improve the effectiveness of compass navigation if and when it is used.

    Yes

    Where I strongly disagree is the idea that proficient map and compass skills are perceived as mainly or only being needed when going off trail. I can think of many times where sight distance or way pts/notable pts of reference were significantly limited or absent ie; deep wide uniformly forested areas, deep wide canyons, large areas of largely featureless granite/lava/ ice/snow, flat deserts, deep fog, mist, heavy rain, falling snow, deeper snow covered landscapes, etc., ALL possibilities or similar in the Lake Tahoe area ie; Desolation Wilderness, Granite Chief Wilderness, Humboldt-Toiyabe/Stanislaus/Eldorado Nat Forests, etc

    Sometimes, you can get away navigating with proficient map reading skills only, IN THE SIERRAS IN THE LAKE TAHOE AREA, like on a TRT thru-hike in Aug, and it certainly is great when that occurs but under some situations it is NOT enough to efficiently navigate. IMHO, proficient compass and map navigation includes BOTH proficient map reading skills and proficient compass skills USED TOGETHER. Yet, there are times when a map is of limited use for navigation in itself.

    YES, absolutely even in the Lake Tahoe area of the Sierras, and especially if your hiking conditions resemble anything I've said or have ANY potential to develop into them, or if you do wish to practice gaining map and compass navigational proficiency, account for magnetic declination(MD). Even though I have done the MD adjustments in my head I much prefer using a compass with adjustable bevel where the adjusted MD can be locked in. It's that much less to statistically account for which might vey well be better as you are newly advancing your map and compass skills.

    Not being able to pinpoint your location can be costly in several aspects. With significant elevation changes, thick forest, vertical escarpments, talus fields, angled slabs, steep ranges, off trail wandering, possible inclement weather, some remote vastness to the west, etc can translate to major time, energy, etc navigational inefficiencies in the Sierras including the Lake Tahoe area,, especially on the western side of the lake.

    Just my opinion and one possible approach.

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    Quote Originally Posted by jefals View Post
    I understand that. I've got my map and course and angles plotted ahead of time . The one thing now I wish I had -- without a GPS - is a reliable method, that doesn't rely on batteries, to know how far I've walked. Hopefully I'll know when I get to certain map landmarks, but I mean the entire way.
    Knowing your pace under different scenarios, over different terrain, weather, etc, can be a critical piece in the navigational puzzle. With limited or no map features or limited visibility, etc knowing my pace, using a watch and compass I've been able to get to my desired destinations with little to no need for a map in route.

    I usually do just as you stated - compare my anticipated or perceived pace, reasonably knowing the distance between starting and end destinations, chunking down a longer distance into shorter distances between known pts. For me, this keeps me more on course. BTW, my course navigation in areas like the Sierras isn't always approached in a shortest line between two pts fashion. Sometimes longer distances mean less energy less time less fatigue expenditure.

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    BTW, the MD is slightly different depending where you are in the Sierras. If I'm recalling correctly I've used from about 12 1/2* to 15*

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    Quote Originally Posted by Dogwood View Post
    . . . Where I strongly disagree is the idea that proficient map and compass skills are perceived as mainly or only being needed when going off trail . . .
    I don't know that we necessarily disagree.

    I suggested that I use a compass mostly when off trail, because, frankly, I can generally see the trail I'm on and know where along that line I am. So I don't need a compass in such conditions. But, proficient map skills are needed to allow me to keep track of where I am. And I do always have a little button compass so I know, in general, which direction is which.

    I also suggested it's usefulness when orienting a map without the ability to see terrain, and I inferred using it when I don't know where I am along a trail.

    Using a compass in inclement conditions, to maintain orientation, when the trail is not clearly marked is another good time to use a compass.

    BUT, in all, during 3-season travel, along well used trails, I have rarely if ever been in a situation where a compass was needed or even all that useful.

    Frankly, there are also times, especially when visibility is poor, if you don't know where you are, a compass is pretty much useless (keep that backup GPS somewhere handy).

    Finally, I hate to bury this idea at the end of this post, but what the heck:
    Some of the most fun I've had and the most useful compass, map, navigational training I've ever had, was my first 100 geocaches that I found using just a map and compass, not a GPS. I highly recommend geocaching with only a map and compass!
    I'm not lost. I'm exploring.

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    Quote Originally Posted by jefals View Post
    Well, the difference between 260 degrees and 273 widens with distance. And, being a novice backpacker I could be wrong, but I would think that difference could potentially be really serious!
    As neshrry61 says, "Also, it is good to remember that keeping yourself found (following your progress on your map) is much better than trying to find yourself after your are unsure of your location." Practice comparing your map with your surroundings constantly until it becomes second nature. They will become one in your mind. Consider the compass a backup you'll rarely use. And don't forget to have fun out there.
    "It's fun to have fun, but you have to know how." ---Dr. Seuss

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    Quote Originally Posted by nsherry61 View Post
    I don't know that we necessarily disagree.


    Finally, I hate to bury this idea at the end of this post, but what the heck:
    Some of the most fun I've had and the most useful compass, map, navigational training I've ever had, was my first 100 geocaches that I found using just a map and compass, not a GPS. I highly recommend geocaching with only a map and compass!
    I know. You were saying that a compass is good when you're off trail. I think you might have been talking about being "purposely" off trail. But I found myself in very similar circumstances that Dogwood was describing -- fields of granite out in the Desolation Wilderness where I was off-trail, because I couldn't figure out where the trail was. I usually found it -- sometimes sooner rather than later. But just thinking that if I have a properly oriented map and compass, and the skills to use them in this situation, I might be able to cross that granite and pick up the trail on the other side easier. We'll see -- heading back up next week.

    As for that stuff about how much fun you had "geocaching" -- OH, GREAT! Another word for me to look up!

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    Quote Originally Posted by Dogwood View Post
    BTW, the MD is slightly different depending where you are in the Sierras. If I'm recalling correctly I've used from about 12 1/2* to 15*
    I googled it and came up with 13degrees, 33 minutes for Lake Tahoe. Don't remember the date, but fairly recent. I've got it set between 13 and 14, and hopefully over the distance I'm going, the difference will be negligible enough... HOPEFULLY!!!

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