Author Topic: Sighting compass to improve accuracy (and realistic expectation of accuracy)  (Read 5575 times)

Chump

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I'm after opinions regarding compasses.


Having switched to a Silva Expedition 4 from a cheaper version I have become more confident in trusting my compass when it disagrees with me - the compass is always right and I am always wrong.


Now, yesterday I decided to brush up on my compass work in preparation for doing some night navigation when the clocks change (this is my attempt to improve my skills so that I can safely venture out in winter conditions eventually). When taking a bearing to bushes/rocks etc approx 150-200m away, I found that it took a long time to be happy that the imaginary line extending from my compass extended directly to the distant object (if I looked along the line 3 times, it would appear extend in 3 slightly different directions). The inaccuracies were small, but would become significant over distances greater than, say 500m.


I know all about, and use, aiming off, attack points etc, but what are people's opinions regarding the level of accuracy one should expect when taking and following bearings? And has any one thoughts on /experience of using sighting compasses (e.g. Silva type 54) for more acquire accurate bearings? 


I tried compasses with mirrors when geological mapping as a student, but found the base plates to be less helpful than those on the more regularly used Expedition 4.

sussamb

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I've used numerous sighting compasses including an Army prismatic compass.  All I think I would safely say is that any bearing you take is likely to be + or - 5 degrees, hence the need for aiming off etc.  Even if the bearing was 100% accurate you're likely not to follow the line directly but drift left or right.
Where there's a will ...

Chump

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Cool, thanks. Your reply was helpful. I suppose that's why keeping nav legs short and using the compass alongside the map, and always questioning whether everything is going to plan (i.e. that the ground and the map agree with each other) are all good ideas.

Welsh Rambler

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A good guide for compass work is Lyle Brotherton's Ultimate Navigation Manual published by Collins. He recommends the Suunto M3 Global http://www.suunto.com/en-GB/Products/Compasses/Suunto-M-3-Global/Suunto-M-3-Global-CM/ which costs around £45.


Regards Keith

Welsh Rambler

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gunwharfman

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I decided to own up. I've never used a compass in my life and only have the most basic idea of how to. I always carry one though and on top of this confession I only have the weakest idea as to how to understand map coordinates. Eastings and westings I'm afraid mean little to me, I have only ever used my eyes, my instincts, read the hike signs and used my phone maps.


So when I read this thread I thought what are they writing about, I still don't know.


To date, I've only been caught out once, on the GR10 in the Pyrenees in thick, thick, fog. Lost the path completely so switched on my Sity Trail app and just followed the blue dot on the screen. When I wandered to the left or right it bleeped me at me, when I was back on track it bleeped at me again.


But, if I can at least justify myself, when I started hiking I made the decision to only hike national trails and other popular walks.


I'm now feeling like a naughty schoolboy.

fernman

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I'm now feeling like a naughty schoolboy.

Ooh, I don't think you'll find one at this time of night! Anyway, you'll go to jail.

Sorry, I couldn't resist it. Seriously now, I'm guessing that your national trails and popular routes are like the circuit I made last month in a much-visited area where all the paths were either stone-chippings tracks anything from 5 to 10 feet wide or repaired with flat rocks so they resembled Roman or Medieval roads, on which it would be extremely difficult to lose the way even in thick mist.
If you go to wild areas where very few people walk, where there are no paths or as is sometimes the case where there are public footpaths that are marked on the map but non-existent on the ground, then using a compass is a must (though no doubt the gps users will correct me).
Even with lowland walking, surely there must be occasions when your footpath ends at the side of a recently ploughed field with no hint of the way further, while the exit on the far side is out of sight over the curve of the land. The obvious thing then is to take a bearing from the map with a compass, so how do you manage?

Pitboot

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To answer Chump;


I've used all types of compass, in the army we used the sighting compass, since then I have used most of the Silva and Suunto range. These days I use the Silva with a sighting mirror, personal preference really, but I also used this type for military activities.
None is more inherently accurate than others IMHO, what matters is your own skill, experience, and confidence. If you are a poor navigator you will not improve by buying  more expensive or technically advanced equipment.
My partner is quite new to hill walking navigation and she gets on really well with a silva type 4.

Chump

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Thanks to all for your replies. I've never used a Sunto, although they are highly regarded, having only used Silvas. I've come across Lyle Brotherton videos in the past but I shall revisit them.


Pitboot, I have found in the past, when I was better practised (although still not good enough for winter), that at least 50% of being confident with navigation is not due to ability/practice, but due to confidence in my ability which comes from practice (i.e. 50% ability 50% confidence in my ability) so it's interesting that you also mention confidence.


I'm going to head out this afternoon for some more practice.

pauldawes

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To answer Chump;


I've used all types of compass, in the army we used the sighting compass, since then I have used most of the Silva and Suunto range. These days I use the Silva with a sighting mirror, personal preference really, but I also used this type for military activities.
None is more inherently accurate than others IMHO, what matters is your own skill, experience, and confidence. If you are a poor navigator you will not improve by buying  more expensive or technically advanced equipment.
My partner is quite new to hill walking navigation and she gets on really well with a silva type 4.


Yes, sure you're right about it being personal preference.


But in days that I used a compass my own preference was for a sighting compass as well. But it's so long since I used it that I had to dig it out to check make...it's a Recta DP2. But such was my weakness for buying compasses in the old days, that I suspect I've also got a Sunta model somewhere.


I was interested in sussamb's view on accuracy (I regard him as really expert on these issues)...and my own view was I'd be pleased to hit his 5% "accuracy target". I have never in my life corrected for magnetic variation, for example.


From memory, that sighting compass was a pretty expensive buy. And although well made compasses are robust and long lived bits of kits, I think I'd be wary...if starting hobby today...about putting down chunky money for a compass, rather than putting it towards a GPS.

jimbob

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Wainwright never used a compass. He never owned a compass.

Too little, too late, too bad......

pauldawes

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Wainwright never used a compass. He never owned a compass.


I once worked with a guy who could just tell direction...with reasonable accuracy..without recourse to any artificial aid...by a method I couldn't understand. (Nor could he!)


I tested him out a couple of times in basements of London skyscrapers we'd never visited before, far away from any external cues such as position of sun.


"What direction are we walking in now?"
Sean would instantly reply something like "Roughly NNE", out would come my compass...and he was always right on times I checked his pronouncements.


Doddy

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Evidently we still have vestigial compass in our brains- a remnant of when it was used much more hunter gathering and earlier. I think we are using this when we know are off-piste and have that uncomfortable feeling the route is not right. A compass and knowing how to use it is essential- what happens when the weather closes in and you lose visibility and direction. Search and Rescue are out virtually on daily basis for people who don't know where they are.

jethro10

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I decided to own up. I've never used a compass in my life and only have the most basic idea of how to.


I'm not in that class quite, but haven't needed to use one in anger for many years.
Technology has moved on and made things way more pleasurable, fast and convenient.
TBH, not sure why folks use them regularly nowerdays. It's not often I see folks using them out in the wild anymore.
Same with my Horse & Cart. no idea where I left it ;-)


J

gunwharfman

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Maybe the skills of using a compass will go the same way as morse code?

 

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