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Brunton 7DNL Compass Review
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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)

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!