Brunton 7DNL Compass Review

Small, light, easy to use, and about the right size for a simple baseplate model.

Recommended

Overall Rating: Recommended

Small, light, easy to use, and about the right size, but skip the supplied cord neck loop.

About This Rating

M Find other top product reviews »

Print Jump to Reader Comments

by Roger Caffin |

Overview

Brunton 7DNL Compass Review - 1
Brunton 7DNL compass, courtesy Brunton.

There are many different sorts of compasses, ranging from tiny button things to great hulking surveyor/military things. In between we have the typical baseplate compasses.

One problem with the tiny compasses is that many of them are prone to sticking if you don't have them precisely level. I've tried quite a few and never been really confident about relying on them, even though they are so ultralight. Another problem with them is that they don't allow you to get a very accurate bearing. In fact, many of them don't have much more than the four (or eight) cardinal points marked on them.

The obvious problem with the big surveyor/military ones is weight. I have an Australian Army prismatic compass which weighs half a ton: it is made from solid brass. It (truthfully) comes from World War II. To be sure, I can read it (and trust it) to half a degree or better, but I don't need that accuracy in the field. I did find it useful for surveying my farm though.

In between we have the broad category of baseplate compasses. These have a disk-shaped liquid-filled module mounted on some sort of flat baseplate and come in a range of weights and sizes. The heavy end is the domain of the mirror and other sighting compasses. I am sure they have a use somewhere, but I find them rather clumsy and impractical. In fact, some of them seem downright awkward or worse. I also find that I can get just as good a bearing from a simpler compass as one of these, so they are just excess weight for me. Perhaps if I was trying to locate myself on a broad flat plain by sighting on distant sharp peaks they might have a slight advantage, but 'flat plains and distant peaks' doesn't describe any of the country I walk in.

That leaves us with the simple baseplate units. Some of these have big baseplates, and others have little baseplates. The argument for the bigger baseplate is greater accuracy, except that I have never found that necessary or even useful, even for tricky navigation. The bigger baseplates also sometimes have a magnifying glass embedded in them: I haven't found that to be a real lot of use either.

Brunton 7DNL Compass Review - 2
Brunton 9030 compass, courtesy Brunton.

In fact, up until recently my favourite 'baseplate' compass did not even have an extended baseplate per se. It was very much like the Brunton 9030 shown here: just the round compass module, rotating inside an outer ring for declination adjustment. Yes, there is a 'baseplate' attached to the black ring under the rotating module, with the logo and arrow on it. I bought mine in France after I (ahem) lost my previous compass in the mountains. I think mine was made in China: it was fairly cheap. I have shown the Brunton 9030 here to illustrate what I mean by a compass without an extended baseplate. But after many long trips in the mountains over many years, my Chinese one started to lose the damping fluid inside the module, and it was time for a new one.

I looked at a range of baseplate compasses. Many of them had long plates with corners. The length can be a bit inconvenient at times, since I usually carry my compass hanging around my neck (a compass is of no use if you can't get at it easily). The corners on the long baseplates can dig into my chest. This model 7DNL is the lightest and smallest baseplate in the Brunton range, at only 25.5 g (0.91 oz).

The rotation of the compass module on the baseplate to set the local declination is really very smooth, but there is just enough friction to keep the declination set. The red ring used to rotate the module is a smooth and tactile polymer band: no sharp corners. It handles nicely.

The markings around the edge have been hot-stamped into the plastic: they are not just painted on the surface. This means it should be a long while before they wear off. One could wish the lines were a shade narrower, but really they don't matter that much. I normally align the compass with the needle anyhow by rotating the whole unit. This automatically corrects for the local declination.

Brunton 7DNL Compass Review - 3
North is THERE??

One thing I did notice was that the needle looks a bit tilted when the compass is flat on the table. The white S-seeking end of the needle points slightly downwards. That means I have to tilt the compass slightly (about 5 degrees) to be absolutely sure the needle is able to swing freely. This isn't hard to do and becomes automatic.

The need for this tilt is hardly surprising, as the magnetic field around where I live (Sydney, Australia) is actually tilted some 64 degrees downwards. That's really pretty savage, so a tilt of the compass needle of 5 degrees is rather small. Actually, all our compasses need a similar amount of tilt to swing most freely, so there is nothing special about this one. Yes, in Europe the tilt goes the other way, as expected.

Brunton supplies a soft red loop of cord which can be used as a neck loop for hanging the compass around your neck. It's a very good idea, and that's how I carry my compass. However, an hour after hanging the compass around my neck, I found the cord was really twisted up something awful. I unraveled all the twists and continued. An hour later, the twists were back: this happened several times in one day. I simply do not know what was the matter with the string, but it was too much for me and I replaced it with my own.

Specifications and Features

BrandBrunton
ManufacturerSilva Production (looks identical to Silva Field 7)
Country of originSweden
Model7DNL
MaterialVarious plastics
Needle pivotSapphire jewel bearing
Graduations2 degrees, hot stamped
Declination ScaleIntegral
Measurement ScalesMetric and Imperial
Size85 x 54 x 9.5 mm (3.4 x 2.1 x 0.37 in)
Weight (claimed)25.5 g (0.9 oz)
Weight (measured)27 g (0.95 oz) with supplied neck cord
MSRPUS$15, but retail US$10 - 12 has been seen

What’s Good

  • Robust
  • Light
  • Easy to use
  • Bold markings

Possible Improvements

  • Slightly finer definition on the printing
  • Better quality string
Disclosure: The vendor provided this product to the author and/or Backpacking Light at no charge, and it is owned by the author/BPL. The author/Backpacking Light has no obligation to review this product to the vendor under the terms of this agreement.

Citation

"Brunton 7DNL Compass Review," by Roger Caffin. BackpackingLight.com (ISSN 1537-0364).
http://backpackinglight.com/cgi-bin/backpackinglight/brunton_7dnl_compass_review.html, 2010-05-25 00:00:00-06.

Print

Reader Comments

You must login to post comments.

New Visitors: Create a new account
Username:
Password:
Remember my login info.

Brunton 7DNL Compass Review
Display Avatars
Sort By:
Addie Bedford
(addiebedford) - MLife

Locale: Montana
Brunton 7DNL Compass Review on 05/25/2010 14:38:10 MDT Print View

Companion forum thread to:

Brunton 7DNL Compass Review

Bill B
(bill123) - MLife
7DNL on 05/26/2010 06:47:14 MDT Print View

Roger,
Great review. I have also found over time that a sighting compass is of little use to me. It souns like from your review that the declination is adjustable, seperate from the rotating bezel, but Brunton's description of the compass says,"fixed declination scale". can you explain?

Nicholas Luhr
(nhluhr) - F
sighting mirror is not an optional part of a compass. on 05/26/2010 07:03:03 MDT Print View

I can scarcely imagine a compass without a sigting mirror to be useful. If you try to perform landfall navigation with a plate-only compass like this, you will have larger average error on each iteration and by the time you have gone far enough distance wise, your total error will have been multiplied many times.

A compass like this is for somebody who doesn't know how to use a compass and is just checking general orientation, not actually using it to navigate with accuracy - In other words, great for somebody who will stay on a trail at all times and has no need to accurately triangulate their position in complex terrain and has no need to follow a bearing with close accuracy for miles of terrain where tree canopy prevents any triangulation.

Jonathan Shefftz
(jshefftz1) - MLife

Locale: Western Mass.
Why the disparagement of mirror-sighted compass models? on 05/26/2010 07:15:32 MDT Print View

Okay, so good to know that the Brunton cheapo light compass is a bit better than the comparable ~$10 competition. I sometimes carry one of these as backup, or when I don't expect to be doing any navigation.
But when I do expect to be doing significant navigation, often following a bearing from the GoTo function of my GPS, I use a more full-featured compass.
So what explains this part of the review? --
"The heavy end is the domain of the mirror and other sighting compasses. I am sure they have a use somewhere, but I find them rather clumsy and impractical. In fact, some of them seem downright awkward or worse. I also find that I can get just as good a bearing from a simpler compass as one of these, so they are just excess weight for me. Perhaps if I was trying to locate myself on a broad flat plain by sighting on distant sharp peaks they might have a slight advantage, but 'flat plains and distant peaks' doesn't describe any of the country I walk in."
-- In short, I'm with Nicholas here. Do these models weigh more? Yes. Bulkier? Yes. But clumsy, impractical, awkward -- how so? The declination is easy & precise to adjust in advance, so one less thing to worry about. The needle balances very well. Sighting through the slot in the bottom of the mirror is very easy.

Chris Townsend
(Christownsend) - MLife

Locale: Cairngorms National Park
Brunton 7DNL Compass Review on 05/26/2010 07:24:28 MDT Print View

I'm not going to knock mirror/sighting compasses but it's false to say they are needed for complex navigation. Orienteers don't use them and their navigation needs to be precise. I've played with sighting compasses but use an ordinary base plate one most of the time and I do a great deal of off-trail hiking in mist on featureless terrain in the Scottish Highlands. I've also taught navigation for ski touring with base-plate compasses. In fact the compass I've used most is the Silva 7 - the same as the one Roger reviews other than the name.

Rog Tallbloke
(tallbloke) - F

Locale: DON'T LOOK DOWN!!
Re: Brunton 7DNL Compass Review on 05/26/2010 07:47:56 MDT Print View

I use a longer baseplate Silva 4/54 model. Not because it has a long baseplate, but because it has tritium markings which help when night walking on a bearing.

There is a guy on UK ebay selling ex army ones ridiculously cheap. item 370372471426

Geoff Webb
(photonic) - F
Re: Brunton 7DNL Compass Review on 05/26/2010 09:40:17 MDT Print View

The need for compass accuracy is a relative thing. Most of my time in the backcountry is spent in places where terrain association is more important than having a super accurate compass. Usually the lake, peak, or col, I'm looking for is large enough that I can find it with the Silva 7 I carry.

I don't usually find myself in trackless desert or jungles where terrain association won't help you. I also don't usually have to find caches of equipment or food. Mirrored sighting compasses are what are needed for these types of activities.

Compasses like Roger reviewed may not be the best for all situations, but I wouldn't say they are only for clueless noobs who never leave the trail either.

As with most things, you need to choose the right gear for the stuff you do, not what some one says you need. Different strokes for different folks.

Edited by photonic on 05/26/2010 09:42:28 MDT.

Nicholas Luhr
(nhluhr) - F
Re: Brunton 7DNL Compass Review on 05/26/2010 10:06:51 MDT Print View

The problem with not having a mirror is you are less capable of taking accurate readings. When you use a non-mirror compass, the only way sight a bearing is to hold it up in front of you and view along the straight edged baseplate... but holding it in front of your eye so this is possible means you cannot see the needle to ensure it is still boxed in the meridian lines and also that it's still free-floating and not just being dragged by friction because your hand isn't perfectly level. I'd be surprised if you can level the compass, box the needle, and then bring it up to view without changing it less than a degree or so. The mirror lets you watch the needle WHILE sighting AND gives you a rifle sight through which you can sight a specific point.

It's one thing to orienteer (determine your position) you can put the compass on a flat surface, move it around on the map, get on your hands and knees to sight along the baseplate for triangulation, etc. I think anybody could do this with a simple baseplate type compass and some arithmetic (to account for declination). Navigation is the process of actually going somewhere and it's a whole different ballgame. It requires you to take readings dynamically and frequently. If you can't rapidly sight a bearing, you won't do it enough and you'll get lost OR you'll do it but will take twice as long to get anywhere. If you can't accurately sight on objects both near and far, your error will continue to compound itself and you'll be way off target, meaning you need to use a very large intentional error to avoid missing your target. Very large intentional error may mean you take far more time and travel much further because you couldn't head more directly to your target.

I can travel over a mile through dense hilly/rocky/forest and streams and come out with an accuracy of less than a half degree error from my starting point because I am able to sight with tight accuracy on objects that are relatively close to me (distant objects being blocked from view) and continue following my bearing with accuracy and precision. That is within 46ft over a mile of difficult travel (clambering over rocks, downed trees, around brushpiles, through streams, etc. How close can you get without a sighting mirror? On open ground with no trees (scottish higlands?) you can sight on something much further, thus reducing the number of chances for error, and get away with it, but then again, in terrain like that, you can see your destination from a mile away so it wouldn't matter. I totally understand what you mean, Geoff... many places the terrain is distinct enough that you don't need anything other than basic terrain knowledge to know where you are. The point is, when you NEED a compass to navigate, you need more than a baseplate.

Also, I don't see an inclinometer on this compass... Knowing the slope angle is a major factor in orienteering (when combined with altitude and/or aspect, you could narrow your location to just a couple possibilities). Seems a crime to omit the 2grams an inclinometer would cost when it provides a relatively useful bit of information.

So in the fervor that is lightweight backpacking, it seems to me efficiency is often overlooked. If you omit the extra three ounces that a sighting mirror costs but then have to travel greater distances (because of intentional error or because you get lost) with less certainty, what's the point? Masochism?

Edited by nhluhr on 05/26/2010 10:10:45 MDT.

E J
(mountainwalker) - MLife

Locale: SF Bay Area & New England
lightest reliable mirror sighting compasses? on 05/26/2010 11:20:08 MDT Print View

Which are the lightest reliable mirror sighting compasses?

Nicholas Luhr
(nhluhr) - F
Suunto MC-2 Pro, Brunton 15TDCL, Silva Ranger CL on 05/26/2010 12:40:08 MDT Print View

The Suunto MC-2 series are around 2.6oz but barely any of them are over 3oz.

There is a graphite-based Silva that is 1.2oz but the opaque base reduces its usefulness on a topographic map and it has no clinometer, and no declination so you're forced to do the math in the field, potentially under duress.

There is also the small Brunton 26DNL-CL which has an opaque base and no declination but does have a clinometer, also 1.2oz.

Personally I just like my Silva Ranger CL. The Brunton 15TDCL is also a gold standard, both of these are 3oz.

Rog Tallbloke
(tallbloke) - F

Locale: DON'T LOOK DOWN!!
Re: Suunto MC-2 Pro, Brunton 15TDCL, Silva Ranger CL on 05/26/2010 15:02:32 MDT Print View

I have a very nice Suunto military prismatic with tritium markings. Only trouble is, it has some obscure number of degrees around it which don't relate readily to 360. What's up with that?

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
Re: Re: Suunto MC-2 Pro, Brunton 15TDCL, Silva Ranger CL on 05/26/2010 15:50:46 MDT Print View

Military compasses tend to be in mils:
http://en.wikipedia.org/wiki/Angular_mil

It's convenient for gauging distances as one mil is one meter wide at one kilometer.

Rog Tallbloke
(tallbloke) - F

Locale: DON'T LOOK DOWN!!
Re: Re: Re: Suunto MC-2 Pro, Brunton 15TDCL, Silva Ranger CL on 05/26/2010 15:56:20 MDT Print View

A neat and accurate reply. Thanks a lot! I'll start carrying the heavy little 3oz beast around and guaging distances for fun. :-)

Chris Townsend
(Christownsend) - MLife

Locale: Cairngorms National Park
Brunton 7DNL Compass Review on 05/26/2010 16:10:01 MDT Print View

Nicholas, I can navigate just as accurately with a base plate compass. It's not difficult. And I never hold the base up to my eye. Also, orienteering is about navigating in woods and finding tiny markers - it requires good skills and accuracy. And as it's competitive orienteers want to find the most direct route. You are confusing it with orienting the map and finding your position.

And in the Scottish Highlands I am often navigating in thick cloud where visibility is down to fifty feet or less. In winter I often navigate in white-outs too.

I've used a Silva 7 compass for around 30 years and never had a problem with it in any type of terrain or visibility. I've never needed a sighting compass.

Edited by Christownsend on 05/26/2010 16:13:42 MDT.

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
Re: lightest reliable mirror sighting compasses? on 05/26/2010 16:25:36 MDT Print View

I like this model:
http://www.amazon.com/Brunton-Compact-Mirrored-Compass-Luminous/dp/B000093ILN

It's also nice in that you can clip it onto your pack strap and it will hold it level.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Brunton 7DNL Compass Review on 05/26/2010 16:30:11 MDT Print View

I agree with Chris, and I have used dozens of different compasses in my life. I think navigating by compass in the Scottish Highlands in thick cloud would be a great challenge (I think that is what the Scotsman calls a fair day). Many of us do more navigation around timberline in the Sierra Nevada, and we can go for days and days without ever picking up a compass at all. Most of the time, I don't bother to carry a compass with declination adjustment, and I just do the math in my head.

--B.G.--

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: 7DNL on 05/26/2010 17:44:29 MDT Print View

Hi Bill

> "fixed declination scale"
Yeah, well, marketing wrote the blurb ...
I think what it means is that there is a fixed set of lines on the base plate, and you rotate the bezel over that to set the declination. Rather standard on any base-plate compass, actually!

Cheers

Edited by rcaffin on 05/26/2010 18:20:20 MDT.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Brunton 7DNL Compass Review on 05/26/2010 17:47:22 MDT Print View

Hi Geoff

> I wouldn't say they are only for clueless noobs who never leave the trail either.
Actually, what we often find is that the more experienced the walker, the smaller and lighter the compass.

For myself, I actually navigate off the sun most of the time. I check once with the compass to see roughly where the sun should be, and then go from there. This works (but see next posting).

Cheers

Chris Townsend
(Christownsend) - MLife

Locale: Cairngorms National Park
Brunton 7DNL Compass Review on 05/26/2010 17:52:21 MDT Print View

"I actually navigate off the sun most of the time"

Roger, how lucky you are! I often navigate off the wind.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Brunton 7DNL Compass Review on 05/26/2010 18:19:13 MDT Print View

Hi Nicholas, and others

> The problem with not having a mirror is you are less capable of taking accurate
> readings. When you use a non-mirror compass, the only way sight a bearing is to
> hold it up in front of you and view along the straight edged baseplate... but
> holding it in front of your eye so this is possible means you cannot see the needle
> to ensure it is still boxed in the meridian lines and also that it's still
> free-floating and not just being dragged by friction because your hand isn't
> perfectly level.

I understand what you (and others) are saying, but there is an assumption here which is not true. You do NOT have to sight along a compass edge to take a bearing **in order to navigate**. How many of us navigate is different, and I will spell out how. (I am assuming off-trail travel here.)

You are travelling along a ridge (or a valley). There is a fork in the ridge or creek. Which one do you take? You don't need sightings to determine that. Or you want to check which side creek you have reached - is the river going north or north-west just here, and the side creek is going in what direction? Side of range - similar comments.

What we are doing here is using the compass AND THE MAP for our navigation. It's no use knowing to 0.1 degrees where True North is if you don't have a map to be able to decide where you want to go. (Alice in Wonderland) Once you combine map AND compass you can navigate using the terrain, matching it against a mental model you have built from the topo map. This can be done while travelling at high speed too.

Yes, there are two problems with the above.
* What if you are in Scotland and there is no sun? Happens. :-)
* What if all you have is a sketch map, without contours? More tricky, but highly accurate compass bearings are unlikely to be much use in that case either.

How do I use a map and compass to locate myself? I rarely take bearings. What I do, and I think I said this in the article, is I use the compass to **align the map** within a degree or two. That is done with the compass lying on the map. The last picture in the article shows me doing this. Then I look around me and use the surrounding terrain to work out where I am. But not just distant peaks (which we don't have anyhow), but also the saddles, spurs, gullies, and even the slope of the land where I am standing.

> I can travel over a mile through dense hilly/rocky/forest and streams and come out
> with an accuracy of less than a half degree error from my starting point
For sure, and we normally do that holding a baseplate compass in one hand while we travel, without taking bearings. In thick scrub. Much faster travelling that way, but it does take practice. Yes, we can and do match that sort of deadfall, regularly. And yes, that is in the Australian bush, where you can't see more than one or two hundred yards at a time anyhow. Thick scrub.

> Seems a crime to omit the 2grams an inclinometer
I can tell from a topo map *roughly* how steep the terrain should be, and I can estimate to within 5 degrees what the local slope is. But topo maps are NEVER that good, and relying on an accurate measurement of slope to determine position is not something I would ever want to have to rely on. Some of our local topos - if there are two 20 meter contour lines close together we know it really means a cliff!
Altitude - yeah, I do carry an altimeter. Useful in some cases.

> If you omit the extra three ounces that a sighting mirror costs but then have to
> travel greater distances (because of intentional error or because you get lost)
> with less certainty
There are two false assumptions here.
* The first is that not having a sighting mirror will cause you to travel greater distance because you have got lost. I dispute that - it doesn't happen to us.
* The second is that having a sighting mirror will get you to your destination dead-on every time. I question that too!

Bottom line: you need compass AND map to navigate.

Cheers

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Brunton 7DNL Compass Review on 05/26/2010 18:22:29 MDT Print View

Hi Chris

> Roger, how lucky you are! I often navigate off the wind.
I was thinking of you when I wrote that!

Yes, I have been walking and climbing in Scotland too. Ice climbing around Glen Coe. I understand ...

Cheers

Dale Crandall
(dlcrandall) - M

Locale: North Cascades
Sighting v baseplate on 05/26/2010 18:43:06 MDT Print View

In this neck of the wilds (North Cascades), nobody gets to walk in a straight line very far. The two purposes of a compass here are to generally orient yourself in the topography, and then to generally follow the chosen topography in the right directions and elevations. The topography always dictates the route, whether on trails or off. I used sighting compasses for a long time for orienting myself, but found I didn't need that much accuracy for that purpose, and found I was tempted to spend too much time looking through the compass instead of walking with awareness of which drainage I was in. Now I use a Suunto A30 (similar to this reviewed Brunton but with a magnifier) on a color photocopy of a portion of a detailed topo map. If you don't have recognizable topography to work with, use a mirrored/sighting compass.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: Brunton 7DNL Compass Review on 05/26/2010 22:24:23 MDT Print View

"Bottom line: you need compass AND map to navigate."

...and you need the skills to put them together.

The modern alternative is GPS. Unfortunately, too many backcountry travelers get totally dependent on GPS, and they let their traditional map and compass skills go bad. Then, when the GPS batteries fail, or when there is a GPS*Blunder*, you can get in an awkward position.

I navigate 90% of the time purely by map and sun angle. Once in a great while, I will pull out a compass to confirm what I already think about bearing. Often I use GPS to confirm what I already think about position.

--B.G.--

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Re: Re: Brunton 7DNL Compass Review on 05/27/2010 01:09:09 MDT Print View

Bob wrote:

> I navigate 90% of the time purely by map and sun angle. Once in a great while,
> I will pull out a compass to confirm what I already think about bearing.

+1

Cheers

eric levine
(ericlevine) - F
Another compass type on 05/27/2010 02:07:02 MDT Print View

If you want the simplicity of a baseplate w/ the ability to sight 1/2 deg. using no skill, give the Brunton (Silva) combi 54 a look. It's a large baseplate with a real sighting compass built in. Weight at 1.3 oz w/o lanyard is not too bad, but the same cannot be said of its price.

Also, no declination adjustment is possible, but I've never found such an adjustment needed. One can always draw in some mag. north lines on the maps; at say, half mile intervals. Or just add/subtract the declination number. That "west best -- east least" thing I've never found usefull. Does it mean field to map or map to field? For those of us in the US west, "first man adam" (field to map add) is gives what you need.

Rog Tallbloke
(tallbloke) - F

Locale: DON'T LOOK DOWN!!
Re: Another compass type on 05/27/2010 02:47:31 MDT Print View

The Nemonics I learned were MUGS and GUMA. Map Unto Ground - Subtract, which seems opposite to your first man adam aide memoire. I guerss it depends whether you regard a westerly deviation as positive or negative number.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Another compass type on 05/27/2010 06:01:12 MDT Print View

> I guess it depends whether you regard a westerly deviation as positive or negative number.

Does it also depend on what the local deviation is? Positive or negative?

Cheers

Nicholas Luhr
(nhluhr) - F
Re: Re: Re: Another compass type on 05/27/2010 07:53:17 MDT Print View

>Does it also depend on what the local deviation is? >Positive or negative?

These kinds of questions are EXACTLY why you should have adjustable declination. When you get lost and you're already running on the amygdala and not the cerebrum, you don't want to depend on questionable mnemonics and potentially careless arithmetic.

Anybody can work it out on paper sitting at the dining room table but when you're wet cold and lost, and you are getting narrowed focus and less ability to process additional stimuli, you DO MAKE MISTAKES.

Chris Townsend
(Christownsend) - MLife

Locale: Cairngorms National Park
Brunton 7DNL Compass Review on 05/27/2010 08:09:19 MDT Print View

It's easy enough to mark declination on a compass with a piece of tape, not that I've ever done this as I don't think it's necessary. Plenty of non-sighting compasses have adjustable declination if you want it though I don't think it's essential.

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
tape or paint marking on 05/27/2010 11:34:22 MDT Print View

For my basher compass that i take on local hikes, i marked it already with the mag dec for my area:marking mag dec on compass

Steve WYSTRACH
(swyster) - F

Locale: some sentier de grande randonnée
Brunton 7DNL Compass Review on 05/27/2010 22:44:05 MDT Print View

My experience is that the type of compass you need is based on the type of navigation you expect to do, plus experience. Personally, I’ve never used the mirror-sighting type on an outing, although they are great for easily taking accurate bearings. On the other hand, I’ve used a conventional ship’s compass to take bearings, and triangulate position, routinely on sailboats – just sighting over the needle to the lighthouse or smokestack.

As for hiking, I’ve walked several thousand miles on the great web of trails in Europe, with only the tiniest of modern compasses. On my first trip, I needed no more than the little button compass that was embedded in my REI trekking poles. It decayed and froze up during the first month. (Incidentally, afterwards, REI told me it wasn’t intended for navigation – hmmn, I thought). Fortunately, I reached Limoges, France, just as that occurred, where I purchased a Recta Clipper compass. It’s sold as the Silva Clipper in the US.

For trail work, with occasional distant bearings, the odd cross-country “short cut”, etc. (with a topo map as Roger says), for 10 bucks and 5.9 grams, it’s pretty hard to beat. It’s been my http://www.longwalking.com compass of choice, still bubble free, for the past 6 years.

So it all just depends on the outing. Thanks, Roger.
Cheers! I hope to see you on the trail. SM

David Corbin
(wildyorkie) - M

Locale: New York
"Brunton 7DNL Compass Review" on 05/28/2010 08:55:26 MDT Print View

Roger wrote: "I have to tilt the compass slightly (about 5 degrees) to be absolutely sure the needle is able to swing freely . . . The need for this tilt is hardly surprising, as the magnetic field around where I live (Sydney, Australia) is actually tilted some 64 degrees downwards. That's really pretty savage . . . all our compasses need a similar amount of tilt to swing most freely"

The reason Roger has to tilt his compass is because the vertical intensity and direction of the earth's magnetic field, the inclination, influences the horizontal plane of a compass needle according to the latitude where it is used.

Some compasses, such as the Suunto M-3G Global, have a "Global Balancing System," which helps keep the needle horizontal at different latitudes.

Two other important characteristics to look for is 1) how quickly the needle centers; 2) how free from wobble the needle is; 3) luminous markings. Also, a jewel bearing may desirable for consistent performance over the years.

john flanagan
(jackfl) - F

Locale: New England
sighting compasses / declination adjustments unnecessary on 05/28/2010 09:19:56 MDT Print View

I'm solidly with the "fancy stuff is fun extra weight but not critical" camp on this one.

Errors in declination settings are easily avoided by scribing Mag North/South lines across the map. Take bearings by aligning the N/S lines in the compass housing with those instead of the longitude lines that form the edges of the map. No math or mneumonics to decide whether to add or subtract declination required.

I've not yet found errors in sighting without a mirror to be an issue in practice. The fact that mirrored sighting compasses are accurate does not prove that simple base plates are not, assuming careful and skilled use. I suppose that the flip side is the fact that I've never had an issue with it doesn't mean that I never will...

Accurate navigation without GPS rests mostly on continuously tracking your position on the map using terrain and other features. Trying to find your position after having the map in your pack for an hour is exponentially harder.

Generally, in my experience the compass comes out mostly in low/no visability situations. Ideally in those situations, you navigate with deliberate error planned in. This means rather than shooting for a single pinpoint on the map, you shoot for catch lines, such as ridges, streams, or given an altimeter, even approximate lines of altitude. A deliberate error (aiming off) of a few degrees ensures that you know whether to turn right or left at your catch line.

When there are no catchlines (eg flat terraine, all bog/no stream or northern forest with kettle ponds, sailing to an offshore bouy in the fog) and there is a critical point to find - the GPS is the best dang thing since sliced bread.

Otherwise, leapfrog navigation works well. This means sending a party member out to the edge of hearing and visability and moving them left or right to align them accurately with your bearing. This is probably the best scenario to argue for precise accuracy, but using a mirror to sight is slow and again, careful use of the base plate accurate enough.

In my view this is one of those recurring topics that has clearly divided camps. The fun is in the arguement - no harm done by adapting either stance or piece of gear. I've not yet heard of a serious mishap in the mountains that was rooted in the kind of compass the victim used. Lack of skill and knowledge...failure to have...failure to use... yes, yes and yes. Having one kind of compass instead of another? No.

Edited by jackfl on 05/28/2010 09:21:20 MDT.

Rod Lawlor
(Rod_Lawlor) - MLife

Locale: Australia
Sacked. on 05/28/2010 10:33:58 MDT Print View

"I can travel over a mile through dense hilly/rocky/forest and streams and come out with an accuracy of less than a half degree error from my starting point because I am able to sight with tight accuracy on objects that are relatively close to me (distant objects being blocked from view) and continue following my bearing with accuracy and precision. That is within 46ft over a mile of difficult travel (clambering over rocks, downed trees, around brushpiles, through streams, etc. How close can you get without a sighting mirror?"

Bloody hell, if I was only that good, my rogaining partner would sack me. He expects 5m (16ft) accuracy over 4km (2.5miles) If we don't walk straight on to a checkpoint, through pretty dense bush, at night, after 14hrs of competition, we're wasting time.

As Roger says, we're using a compass (baseplate) for general direction, but primarily running to the map. If we're traveling fast one of us will read the map, and the other one will read the ground.

I do like declination adjustment though. It's faster, and saves screwups at 3am.

Joshua Gilbert
(joshcgil2) - F

Locale: Seattle
bells and whistles on a compass on 05/28/2010 11:02:23 MDT Print View

+1 on the idea that mirrors, declination adjustment, and clinometers are fun but not needed.

I took a wilderness navigation course with the Seattle mountaineers last fall, just to brush up on some skills and to actually get some formal training for once. They required that your compass have adjustable declination, so I had to buy a suunto mc8 (or something, can't recall right now; a baseplate compass w/no sighting mirror) as my old Silva sighting compass didn't have declination adjustment (just the red numbers inside the housing)

I found it pretty easy to travel overland using a baseplate compass w/no mirror, and I came out just about dead on (maybe 1/2 a degree over 1 mile, I was about 3 feet away from the marker) I know experienced orienteers do better, faster and with less.

I've done more complex stuff with a mirror, but I was less experienced then as well.

Nothing wrong with any extras on a compass, they are fun to play with, but saying you must have them is a little excessive I think.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Sacked. on 05/28/2010 22:26:52 MDT Print View

Hi Rod

> He expects 5m (16ft) accuracy over 4km (2.5miles)

Way back ... in Boy Scout days ... we were set a navigation exercise. In brief: we were allowed to study the map for a 3 km trip for about 10 minutes. We were told our start and end positions. Then both the map and the compass were taken away.

So we had to navigate using terrain and the stars. Oh yes - I forgot to mention: this was done at night! No sun, no visibility. Use the stars to determine the South Pole.

I was half way there when I realised I had not allowed for the 11 degrees of magnetic declination ... Ah ... right. Alter course by about 22 degrees and set off again.

But we could cheat near the end, because we could smell the sausages being cooked for our dinner. Despite the error I was within 50 m. Yeah, we all got dinner.

Cheers

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
Using GPS as a compass on 05/31/2010 14:56:26 MDT Print View

This is way off topic now, but here's a dorky exercise: Using a GPS as a compass. If you want to get a good prelim bearing on a tower for a microwave path, you can't use a compass anywhere near it because the steel structure will mess up the magnetic field. So get a GPS fix at the base of the tower, walk out a hundred yards or so and then use goto to the base waypoint. Walk back and forth until you get a good estimate of the bearing (it's a reverse bearing actually.) Put a flagged stake there, and then repeat the process another 100 yards out. This works pretty well and of course the final aiming is done by maxing the signal strength...

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Using GPS as a compass on 05/31/2010 15:16:06 MDT Print View

> the steel structure will mess up the magnetic field
The steel structure may also upset the GPS signals, under some conditions.

Cheers

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Using GPS as a compass on 05/31/2010 21:22:00 MDT Print View

"The steel structure may also upset the GPS signals, under some conditions."

I could not agree any more. I've been responsible for thousands of GPS antenna installations, and a percentage of them have been on, in, or around steel towers. The tower can directly block GPS reception in some cases. More often, the flat steel surfaces cause multipath interference. So, if you have an extremely expensive choke-ring GPS antenna, you can keep working. If you have a simple portable GPS receiver... forget about it.

Further, during a storm, the steel tower tends to act like a lightning rod, so that is the last place where I want to be.

--B.G.--

Paul Davis
(pdavis) - M

Locale: Yukon, 60N 135W
Compass Considerations for the Canadian North... on 05/31/2010 23:53:56 MDT Print View

Thanks to Roger for a great review!

I admit that I often leave a Suunto MC2-G compass at home and rely on the one in my Doug Ritter survival kit---a quality 'button compass'.

Having said that, there are some advantages to using a sighting compass with a mirror in the Canadian North.

First of all, the declination here can vary enormously withing a 1 hour flight time of here, so dialing it in on a fixed scale with the metal-tooth-pick-style declination screwdriver on the compass lanyard avoids much accidental idiocy.

The 'G' series Suunto compasses have a 3D gymballed needle that is truly global in terms of magnetic flux; it will continue to float freely up to about 20° off of the horizontal. This is also useful to those of us who have a hand tremor or are otherwise horizontal-levelling challenged. It will also function closer to the magnetic pole than most compasses which peg-out when confronted with downward-angled magnetic force lines...

Sighting mirrors are still useful, as off the tiny Northern road network we really do still triangulate from known points, do a 'cocked hat' of 3 bearings, to fix our position. We also signal aircraft with the mirror, or discover how shocking we look before heading into town...

The MC-2G, or for that matter the Brunton-Silva Type 15 Ranger, have compass bezels with lugs on them big enough to be used whilst wearing contact gloves or mittens, and are luminous enough to be useful in subarctic darkness.

Oddly enough, I find the opaque cover of the sighting mirror to be an ideal place to epoxy a velcro patch, such that the compass hangs on a velcro patch on my left pack strap, attached by its lanyard against loss, so no strap-around-neck issues! I don't know how I could do this with a baseplate compass without a mirror cover!

Compass bubble issues are not that difficult to solve---Silva cheerfully replaced my 'capsule' after far too many Canada-Africa aircraft flights which led to bubble development, so 're-capsule' before replacing a compass! My Silva 15 Ranger survived 30 years of service, and is on its 2nd capsule, now serving another user in The Pas, Manitoba...

Here, we use the clinometer for risk evaluation for avalanches by checking slope angles.

Thanks again to Roger for a great review, and to all of you for interesting comments!

Rog Tallbloke
(tallbloke) - F

Locale: DON'T LOOK DOWN!!
Re: Re: Re: Another compass type on 06/01/2010 01:51:33 MDT Print View

>I guess it depends whether you regard a westerly deviation as positive or negative number.

>Does it also depend on what the local deviation is? Positive or negative?

Well it's either going to be westerly or easterly. Unless it's zero.

I find it easiest to visualize the problem rather than rely on mnemonics myself. If the deviation is westerly, and I'm heading north, then if I set the compass to the map gridlines, I'll end up walking west of north. Therefore, I need to add the deviation to the bearing to end up going north.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Compass Considerations for the Canadian North... on 06/01/2010 01:58:41 MDT Print View

Hi paul

Thanks for the comments. Just one thing:

> dialing it in on a fixed scale with the metal-tooth-pick-style declination screwdriver
I'm not familiar with this at all, at least on baseplate compasses. Hum?

With the Brunton I set the declination using the red ring and the gradation under it, and then line up the needle with the lines/arrows on the rotating bit; then the base plate is True North.

Cheers

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
adjustable vs fixed dec compasses on 06/01/2010 09:31:52 MDT Print View

These two compasses are doing the same thing, albeit in slightly different ways:
two compasses

The one on the left is a fixed dec, the one on the right an adjustable dec. The point is that you preset the mag dec on the adjustable beforehand and then line up the needle to the adjusted marks, in this case, the yellow fluorescent lines. On the fixed dec, you have to line up the needle to the dec scale each time.

The sharp eyed may notice a few other things:
1) The compasses are doing the same thing as the north mark on the map, this is a quick check that your compass is set up correctly for your region.
2) The bubble is deflecting the left compass's needle slightly and the right compass's marks don't line up due to the camera not being exactly above it (a problem that is solved when using the sighting mirror.
3) You can't get two compasses this close without them interfering with each other, what you don't see in the photo is the 5 minutes it took lining them up.

Edited by erdferkel on 06/01/2010 09:43:22 MDT.

Rod Lawlor
(Rod_Lawlor) - MLife

Locale: Australia
Suunto MC-2G Global Compass on sale on 06/01/2010 15:16:58 MDT Print View

Suunto MC-2G Global Compass is currently on sale at theclymb.com for $40, until Fri 9am I've never used the site, but am registered there. It's members only, but you can use this link

http://www.theclymb.com/invite-from/RodLawlor

to skip past the registration process. (Be aware that this will credit me with $10 for anyone who makes a purchase. I'm not sure how this will work, since they only ship within the US)

Roger, I realise this should be in Gear Deals, but it seemed relevant here. I'm happy to remove it when I get home tonight if you'd prefer, or for you do so.

Rod
------
Relevant.
Cheers

Edited by rcaffin on 06/01/2010 16:28:53 MDT.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: adjustable vs fixed dec compasses on 06/01/2010 16:40:57 MDT Print View

Hi Tohru

The compass on the left is pretty much a generic design - available under most brands with minor variations in colour and trim. The bezel on it CAN rotate and be set for declination. There is a white line under the N symbol which serves as the marker when you rotate the dial.

The Brunton 7DNL is essentially the same. The bezel rotates to set the declination. The blue line points to the marker. You line up the needle with the lines on the rotating bezel.
Brunton 7DNL compass with declination marker 8546

If the bezel on such a compass does not rotate, it is because it is jammed. Sand, dirt etc.

Cheers

Edited by rcaffin on 06/01/2010 16:42:33 MDT.

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
Re: Re: adjustable vs fixed dec compasses on 06/01/2010 16:51:45 MDT Print View

RIght, the baseplate can be set such that you are compensating for mag dec as in your picture. But this means that the baseplate is set to true north only. This is fine if all you want is to orient your map to true north.

The purpose of the dec scale on your fixed dec compass or the adjustable dec is so that the _capsule_ of the compass is set to true north and the _baseplate_ can be set to an arbitrary bearing.

This is so that if you see a mountain off in the distance you line up the baseplate to the mountain, and the capsule to north to get the bearing, which is indicated by the white line you pointed out. Then you can transfer that to your map. Or vice versa, see:
link to Silva 123

Edited by erdferkel on 06/02/2010 11:08:47 MDT.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Re: adjustable vs fixed dec compasses on 06/04/2010 16:54:19 MDT Print View

Hi Tohru

> all you want is to orient your map to true north.
Describes me perfectly. In fact, my wife insists that we do that FIRST, every time.

Then we sight over the map to any peak. Works great for us.

Cheers

Kenneth Linden
(kennethlinden) - F
Declination change with time on 06/05/2010 00:42:59 MDT Print View

Hi Tohru,
Being a southern California hiker, I couldn’t help noticing that the map you set the two compasses on in the picture above is out of date with respect to the magnetic declination shown on the map. For the San Gabriel Mountains, the magnetic declination is now 12.5 degrees, rather than 13.3 degrees as listed on the map, a difference of almost a degree http://www.ngdc.noaa.gov/geomagmodels/struts/calcDeclination. The declination changes a little year over year.
Having said this, I realize from the above Forum posts, that one group, the baseplate compass group, will be gnashing their teeth at the over-exactingness of it, while the other group, the sighting mirror camp, will take it as a matter of course that one would correct for the current declination adjustment.
Personally, hiking in the San Gabriels and other major mountain ranges in So. Cal., I don’t believe I have ever needed to take my compass out of its case to navigate. The land forms are distinctive enough that I just use the topo map and compare it to the landforms, with the sun as compass enough. The only times I have used the compass is to identify some peak on the distant horizon for interest’s sake by later at home using the bearing and Google Earth (most of these peaks of interest would be off the edges of my topo map). For the record, I use a sighting mirror compass, the Suunto MC-2. I like the clear baseplate, the ability to adjust the declination, the clinometer for avalanche considerations, and I like the idea of carrying a mirror anyway for the reasons mentioned above.

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
Re: Declination change with time on 06/05/2010 01:40:53 MDT Print View

Hi Kenneth, yeah, it's a Tom Harrison map of the Angeles and you can't easily see it but it does say 2007 mean declination. In point of fact, these compasses aren't better than a couple of degrees accuracy anyway. To do better you would need to break out the surveying tools or a Brunton Pocket Transit, and that's not exactly ultralight. Not to mention having to worry about local magnetic anomalies.

I've never needed to know more than vaguely where north is while hiking here locally either, the sun and the time does a reasonable job at that. If you're paying attention to where you're going and where that is on the map, then like Roger said, you only really need the compass to orient the map.

But in other terrain that's featureless or where landmarks can become obscured by fog, sand or trees, a compass would be much more useful. It's good to occasionally do the exercise of getting a fix on your location by triangulation. For that, an adjustable dec makes it easier.

Paul Davis
(pdavis) - M

Locale: Yukon, 60N 135W
Suunto MC-2G or Ranger Decl., why we carry compasses... on 06/08/2010 23:28:45 MDT Print View

Roger: I think the declination thing was answered with the excellent photo above---thanks all---both the Suunto MC-2G and the Silva or Brunton Type 15 (Ranger) compasses have a separate clear baseplate which can be swung around by means of a tiny rack and pinion gear, accessed by a tooth-pick style screwdriver on the lanyard, such that even the terminally-tired cannot screw up the declination...works like a charm!

My delay in responding is partially because I have just carpooled 500km N. of here at 64N Tombstone Terretorial Park on a wildlife-watching tour.

Anyways, not being the trip leader, and being sleepy, I left my survival kit in my tent, and did not (gulp!) bring the Suunto with me. +5C rain, fog, 2000M above sea level, lowering clouds.

Group leaders wanted to go up, did not perceive the visibility lowering, though I pointed it out.

Ended up lingering for lunch lower down with a botanist, saw the hikers higher up get swallowed by the clouds, so laid out the bright yellow foam sitz-pad, blew the whistle, and they vectored themselves in by sound.

None had a compass, nor a GPS, none had taken a back-up bearing on the micro-wave relay tower road which was our jumping-off point. This is a trail-less, featureless tundre landscape.

I had a GPS and an Iridium Satphone, so I used the GPS to generate a back-up bearing to get us back to the tower, once they got back to me, as I was below the cloud level.

Memo to self: 'No group hikes without carrying Suunto'!! Even if I am not leading!

Yes, this is why we carry them: dial the declination in, take an insurance bearing with the mirror on your start point, close the lid, and if the fog comes down, open the lid, put the N needle in the S end to create a reciprocal (go home) bearing, use the mirror to choose a bearing marker, even use a hiker 'no, bit to the left, good, stop!', then hike to them, repeat as neccessary...

Get out on the land!

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
re Adjustable declination on 06/09/2010 01:58:58 MDT Print View

Hi guys

I had to stop and think about this issue of the separate declination adjust by screwdriver bit. Why have we never been worried about not having it?

Then the answer came to me: because it is completely unnecessary in the field. That's right, you don't need it at all (at least when walking on land). I had better explain why.

When you are navigating in the field the only thing you have for getting a bearing is magnetic north. 'True North' is an artifact of no relevance at all to practical navigation EXCEPT when you orient your map. That's ALL it is useful for.

Some might argue that without True North you won't have a grid to get grid references off. That is not true either. The grid is related to various survey and geographical things, but principally it too is an artifact of the map makers. In fact, on many maps you find that there are not two but three arrows in a group at the bottom of the map: True North, Grid North and Magnetic North. When this happens you don't care at all about True North: you have to use Grid North. But you won't find grid lines on the ground either.

So, step 1: Orient the map allowing for magnetic declination. You can do this by setting the bezel for the declination, or you can do it using the arrows at the bottom (side?) of the map, or you can just estimate it. Once you have oriented the map, don't move (rotate) it any more!

Step 2: Work out what bearing you want to go on in terms of magnetic north. You might do this for instance by lining up the baseplate between where you are now and where you want to end up. Alter the rotating bezel so the lines on it line up with the needle.

Step 3: Travel keeping the baseplate aligned with the needle.

If you want to set a back-bearing, do it directly: point the base plate and rotate the bezel. You are going to navigate off the local magnetic field after all.

Yes, this means I USE the rotating bezel. It's not just for setting a declination: it's also for setting a bearing. All you have to do is to stop worrying about True North and Grid North, and use Magnetic North. After all: it's all you have really.

I don't know of anyone walker in Oz who has a compass with a lockable declination bezel - in fact I don't think I have ever seen one in the local shops. Too heavy, too expensive. Go light-weight in grams and dollars.

Cheers

Robert Blean
(blean) - MLife

Locale: San Jose -- too far from Sierras
Re: re Adjustable declination on 06/09/2010 06:30:33 MDT Print View

Roger,

Perhaps some find it either easier or more precise (even if not essential) to use a settable declination. Once the declination is set, the latter part of your Step 2 can be changed to read "Alter the rotating bezel so the lines on it line up with the top of the map (or grid lines, if available)."

Doing it this way would mean there is no need to orient the map to find a bearing from it.

--MV

Edited by blean on 06/09/2010 06:33:46 MDT.

Daniel Goldenberg
(dag4643)

Locale: Pacific Northwet
Re: re Adjustable declination on 06/09/2010 08:12:06 MDT Print View

One easy thing to do is to draw in on your map (use the small arrow if it's there) a few grid lines aligned with magnetic North and use those grid lines to orient the map to magnetic north instead of true north. You really only need to draw in one or two lines. Then you don't even have to worry about magnetic declination when orienting your map.

And of course, if you are using the compass to take a bearing to follow, magnetic declination is irrelevant. It's only when the map comes into play that you need it.

Edited by dag4643 on 06/09/2010 08:13:59 MDT.

Chris Townsend
(Christownsend) - MLife

Locale: Cairngorms National Park
Adjustable Declination on 06/09/2010 08:27:26 MDT Print View

I do the same as Roger except that I adjust for declination after taking the magnetic bearing and with no reference to the map. This has always worked well for me and only takes a few seconds.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
The worst part of this on 06/09/2010 10:55:26 MDT Print View

The worst part of this is that some beginners are reading this and won't figure it out. You notice that several experienced navigators each have different methods for adapting to declination, and they probably all get good results. This multiplicity of methods is so confusing to the beginners. Unfortunately, when a beginner takes a Land Nav class, he will be taught only the method that the instructor likes, and that may or may not be the easiest to learn.

I work differently. I think I have a piece of lodestone in my head.

--B.G.--

Chris Townsend
(Christownsend) - MLife

Locale: Cairngorms National Park
Compass Use on 06/09/2010 11:27:06 MDT Print View

Lacking a lodestone in my head I use the Silva 1-2-3 system, which I learnt sometime in the 1970s. It still works!

http://www.silva.se/upload/Catalogues/123_eng.pdf

There are other map and compass techniques of course but this is the basic. The difference between Roger and me is only to do with when to adjust for declination. Taking a bearing from the map is the same.

I've taught navigation (and written about it several times in books and magazine articles) and always use this as the starting point when introducing compass use. (I actually start with just map use).

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
Navigating vs surveying on 06/09/2010 13:11:38 MDT Print View

I don't think I'm in disagreement with Roger and certainly there are many ways to do this: hike your own hike. But I suppose the issue is whether one considers triangulating your position as a navigation task or surveying task.

ROger is correct that magnetic north is just as good a reference if what you are doing is transferring a bearing to navigate to a destination, in fact, air navigation charts have their compass roses set to magnetic. And as Daniel has pointed out (and i've read this in some books on navigation) you can easily mark your map with mag dec parallels as a reference.

But most maps are aligned to true north and to transfer bearings one either has to add/subtract a mag dec correction or use a compass which does it for you. When you are taking several of them to plot a fix, the math can get tedious.

I agree that I've never had to get a fix in normal hiking, usually the terrain features and a rough estimate of north is good enough. But I have practiced getting a fix by triangulation and for that and adjustable dec compass makes it a lot easier. IIRC, triangulation is a requirement for Sierra Club leader checkout...

Actually, the real convenience here is that a baseplate (or mirror sighting) compass is really two instruments in one: a compass and a protractor (fulfilling lightweight backpacking principles!). Having a separate capsule and baseplate which rotates around it is the trick. Without it, you would have to measure the bearing angle on the map with a protractor, add/subtract the mag dec, then modulo 360 to get the number the compass needle has to be pointing at for the 0 mark to be your bearing. Reverse this procedure and repeat for each bearing for your fix!

Tom Kirchner
(ouzel) - MLife

Locale: Pacific Northwest/Sierra
Re: Re: re Adjustable declination on 06/09/2010 18:08:35 MDT Print View

"One easy thing to do is to draw in on your map (use the small arrow if it's there) a few grid lines aligned with magnetic North and use those grid lines to orient the map to magnetic north instead of true north. You really only need to draw in one or two lines. Then you don't even have to worry about magnetic declination when orienting your map."

If you choose to do this it might be good to do it with an eraseable pencil, otherwise you'll end up with either a lot of lines on your map or an inaccurate declination over time. Magnetic declination is not static. It changes from year to year.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Navigating vs surveying on 06/09/2010 21:09:34 MDT Print View

Hi Tohru

> But most maps are aligned to true north
Sorry to have to disagree, but in fact very few maps are really aligned to 'True North'. Really only happens for the maps very near the national Datum.

Have a close look at any map handy and you are likely to find that the map has arrows for True North and Magnetic North beside the Grid North arrow.

> you would have to measure the bearing angle on the map with a protractor,
????
I don't even own a protractor (or if I do I don't know where it is).
I use the map and compass as I described. The compass has its own protractor built-in.

Cheers

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
Re: Re: Navigating vs surveying on 06/09/2010 23:37:34 MDT Print View

>> But most maps are aligned to true north
>Sorry to have to disagree, but in fact very few maps are >really aligned to 'True North'. Really only happens for >the maps very near the national Datum.

I'm referring to the map, not the grid. Maybe this is a regional difference, here the US Geological Survey maps are aligned with latitude and longitude, thus true north. The USGS 7 1/2 minute series are just that: 7 1/2 minutes of angle in both lat and lon.So lines drawn parallel to the sides are aligned to true north.

If you are using the grid on your map, for us the UTM grid, then it is true that the grid will line up with true north in some spot in the zone, but be slightly off everywhere else.

Daniel Goldenberg
(dag4643)

Locale: Pacific Northwet
Re: Re: Re: re Adjustable declination on 06/10/2010 08:52:49 MDT Print View

"If you choose to do this it might be good to do it with an eraseable pencil, otherwise you'll end up with either a lot of lines on your map or an inaccurate declination over time. Magnetic declination is not static. It changes from year to year."

True that magnetic deviation is not static but I wear out a map long before there's a need to change any magnetic north gridlines. :)

Paul Davis
(pdavis) - M

Locale: Yukon, 60N 135W
Grid North, True North, Declination, UTM Grid on all topos in Canada on 06/13/2010 19:01:50 MDT Print View

All: I should have pointed out that we like compasses with built-in declination, as all Canadian topo maps are printed with a 1000 Metre Universal Transverse Mercator Grid, and a handy arc showing how far off this is from Magnetic North, and True North.

So, no pencil lines in Canada! Use the UTM grid! Mind you, the place was only completely mapped in the mid 1980's, and many of our 'maps' North of 60 are 'photo maps', meaning top-line versions of aerial photos from the 1940's!As well, nothing more detailled than 1:50,000 for the Can. national topo system (a few mine areas=1:25,000!)---I envy European and orienteering maps at 1:10,000!

Always having UTM grid available on a map means pretty much always using the Silva 1,2,3 system to get around.

You do need to note which UTM Zone you are in, as the UTM grid numbers do repeat---we use Lat. + Long. for setting up stuff with aviators...

I used the Suunto today for an insurance bearing when coming down from above treeline via a braided horse-foot-ATV series of trails, worked like a charm. Didn't even have to stop walking!