Built-in Declination adjustment - why wouldn't one use it?

Good pointer on declination as these days many folks do not have USGS topographic maps. One needs to know which way to adjust their declinaton on their compass which is why I think many do not adjust their compass.
 
So far, I've been looking up declination for the specific area the map covers (using NGDC), then drawing my magnetic north lines on the map based on that declination using a protractor or the (baseplate) compass itself. A lot easier and safer for me than doing calculations to compensate...more calculations = more chances to make a mistake. I never trust the declination given on maps either. For example, I have a USGS topo covering a favorite state park, and the declination on the map is 15 deg 30' E (1997 topo). Later, I purchased a trail topo map from the park's headquarters... 17 deg (no idea how old that one is). Currently, by NGDC, the declination is 13 deg 59', changing by 5' W per year .... :)

I'm getting lazy in drawing in lines on my maps, so I'm thinking about switching over to using the declination adjustment on my compass. Doesn't seem like I'll lose anything in accuracy (if anything I think I'd gain, by eliminating potential error introduced by drawing MN lines on my maps). I just have to remember to adjust it again for new areas when traveling out of my normal area.
 
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Question,

What do you Guys use?
The Declination correction is from Magnetic North to True North?
Or Magnetic North to Grid North?

(Grid North are the lines on the map)

I was taught and have always used Magnetic North to Grid North
 
Built in declination adjustments like the one in my Suunto MG-2 are a welcome improvement over previous models. As far as I can tell, it's not a gimmick, rather, a pretty useful feature.
To answer your question, I don't know why you wouldn't use one. Forgetting to reset or account for local declination is like forgetting to put gas in your car.
However, if you've been doing well without one and can do the arithmetic in your head, then more power to you.
Map and compass navigation is more that shooting bearings, adjusting declinations, and putting "red fred in the shed."
 
neeman said:
Question,

What do you Guys use?
The Declination correction is from Magnetic North to True North?
Or Magnetic North to Grid North?

(Grid North are the lines on the map)

I was taught and have always used Magnetic North to Grid North
Click to expand...

I've always learned it as Magnetic North to True North. The lines on the USGS maps I have run True North, not Grid North, unless I'm wrong... I'll look at it again when I get home tonight. I don't think I have UTM grids on my maps.

ETA: Nope, I'm wrong. The grids on my USGS maps are UTM. Hasn't mattered so far with drawing magnetic lines on the maps based off declination from true north (used neatlines as a guide). Maybe I'll just stick to drawing MN lines based on True North, rather than set myself up for possible confusion.


JohnWayne360 said:
Built in declination adjustments like the one in my Suunto MG-2 are a welcome improvement over previous models. As far as I can tell, it's not a gimmick, rather, a pretty useful feature.
To answer your question, I don't know why you wouldn't use one. Forgetting to reset or account for local declination is like forgetting to put gas in your car.
However, if you've been doing well without one and can do the arithmetic in your head, then more power to you.
Map and compass navigation is more that shooting bearings, adjusting declinations, and putting "red fred in the shed."
Click to expand...

Thanks JohnWayne. I don't do it in my head, like I said, I have been drawing MN lines on my maps. But yeah, I guess it isn't likely I'd forget. I have no experience with it; I haven't traveled much since getting compasses that have that feature (and before that I can't say I knew much of anything about map and compass). I know there's more to it than "shooting bearings, adjusting declinations, and putting "red fred in the shed," but this is the best place for me to have small questions answered. :thumbup:
 
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HikingMano said:
Thanks JohnWayne. I don't do it in my head, like I said, I have been drawing MN lines on my maps. But yeah, I guess it isn't likely I'd forget. I have no experience with it; I haven't traveled much since getting compasses that have that feature (and before that I can't say I knew much of anything about map and compass). I know there's more to it than "shooting bearings, adjusting declinations, and putting "red fred in the shed," but this is the best place for me to have small questions answered. :thumbup:
Click to expand...

Sorry if that sounded patronizing in any way, not my intention. ;)

A better question would be: Who uses the built in clinometer in their compass? hehe
 
Not at all, and again, thanks for answering the original question :thumbup: :)

As for the inclinometer, nope, not me, haha. Eventually.
 
Completely forgot about this GREAT set of vids by Brian Andrews :thumbup: I remember he talks about declination in them and the pros and cons of different methods. "Declination Part 2" is particularly relevant to my question, if I remember correctly. Going to watch them over now.

[youtube]-NZBMZSwkDY[/youtube]

[youtube]n1gSCVl7eTw[/youtube]

[youtube]oRvA5WElzUQ[/youtube]

[youtube]RhszoJUvLaE[/youtube]

My USGS Maps have UTM grids on them. If I want to use the compass declination adjustment method, I'd have to connect longtitude ticks and add in a few parallel lines (only 2.5' ticks provided), or use declination between Grid North and Magnetic North. There isn't much difference in my area between Grid North and True North (only about half a degree). I'll try both.
 
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The British Ordance Survey maps have at the side of the map, the angle set by the year of printing for Grid North, True North and Magnetic North.
They also give the shift per year

Makes it easier
 
Same for USGS maps, except for the shift per year. Doesn't the rate of shift change over time though? Anyway, I just look up current declination for each area.
 
HikingMano said:
Same for USGS maps, except for the shift per year. Doesn't the rate of shift change over time though? Anyway, I just look up current declination for each area.
Click to expand...

I always wondered why the USGS maps didn't put the declination shift on there. Even the brand new ones don't have it. It would make life a lot easier! Don't the US military maps usually have the annual declination shift?
 
Even the new digital topos don't have them? Digital topos aren't available for my area yet, so I haven't looked. I don't have experience with the military maps, maybe someone with that background can chime in :thumbup:

I don't know how useful it'd be though, if the rate of shift changes over time. Even if they did print them on the map, it'd only be good for a finite period of time. Applying the shift later, after the rate of shift has changed significantly, could mess you up.

As an aside, this site claims to be better than the NGDC prediction by calculating the actual declination based on the World Magnetic Model.
 
HikingMano said:
As an aside, this site claims to be better than the NGDC prediction by calculating the actual declination based on the World Magnetic Model.
Click to expand...

Thats awesome! There's a freeware program out there I think its called Geomag too. Works awesome if you need declination anywhere on the globe. But the USGS site works fine if you are in the USA.

The new USGS digital maps are all dated 2010 or 2011, so we shouldn't have to worry about the declination change too much (yet). Maybe they can update the maps yearly so we don't need the annual change?

But the new maps have a long way to go. The maps for my area are so inaccurate they are borderline useless. My neighborhood alone has over a dozen roads on it that don't exist! I'll stick with the old maps for now(which you can also download for free).
 
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