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I have an Iphone 12 which has a compass app. I've tried it out against city streets that have a known directional angle and it seems to be accurate. But the paper map orientation course still wants you to bring a physical compass so I imagine there is a difference.

So assuming I have an advanced smartphone with a built-in compass, would I still want a traditional one as well? I am aware that the phone is less reliable but are there other reasons too, such as accuracy or ease of reading?

WedaPashi
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JonathanReez
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    I find there is some irony in the fact that you are signing up for a paper map course but are trying to use a phone compass. – noah Jul 15 '21 at 20:50
  • More generally: Don't cut corners on safety gear! – Loren Pechtel Jul 16 '21 at 01:49
  • Some of the discussion under your earlier question about paper map skills is relevant. A few people posted interesting comments, e.g. under my answer – Chris H Jul 16 '21 at 11:30
  • When you compare compasses in the field, don't hold them close together. I tried mounting a button compass on my bike, on a plastic and aluminium phone holder mounted on aluminium aero bars (much of the bike is steel, limiting my options). It was great, until I put my phone in the holder, when it gave me complete nonsense. It did turn as I turned, but not to point the right way, so the fields form the phone and Earth must have been comparable – Chris H Jul 16 '21 at 11:33
  • @MartinF: Hi, I have deleted the comment because if felt pretty direct. We appreciate and encourage participation but at the same time, direct comments (possibliy offending a user) which are not relevant to original post seems to add no value but tend to generate a lot of controvercy. I suggest, pop-in to The Base Camp and clear any misunderstandings (if there are any) over there in a polite and amicable way. – WedaPashi Jul 17 '21 at 07:54
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    @JonathanReez: I could see a couple of downvotes to the question. IMO, it is because if tends to sound opinion-based, although it is not entirely that way. I am going to edit the tile in a way that stages it better. You can revert back if you disagree. – WedaPashi Jul 17 '21 at 07:57
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    @Gabriel: Deleting the first comment as if felt pretty direct for no apparent reason. – WedaPashi Jul 17 '21 at 07:59
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    This is a mind-boggling question. I am pleased to see @Gabriel answering it with grace. It staggers me that people would still try and find a way to not bring a $10, 1 oz piece of equipment that has served humans for hundreds of years and does not fail. Invert the question, what benefits could a cellphone compass possibly have over a physical one? – Venture2099 Jul 19 '21 at 09:33
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    A quick browse shows the OP posting several questions and comments trolling this kind of mentality. Imagine wanting to carry excess weight and power into the wilderness... – Venture2099 Jul 19 '21 at 09:46
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    @Venture2099 if the OP is coming from a mindset that defaults to a tech solution, and hasn't been through the traditional routes to develop outdoor experience, the questions make a sort of sense. Those of us who learnt to navigate with map, compass, and observation, perhaps even (like me) before handheld civilian GPSs even existed won't see it the same way. While in this case I believe we're unambiguously right, that doesn't mean no one should query our reasoning, or ask us to explain the parts that aren't obvious to them. – Chris H Jul 20 '21 at 14:47
  • @JonathanReez mapping of human geography is pretty decent these days, and I can carry huge areas of OpenStreetMap offline on my phone to avoid roaming charges and battery hassles when I travel abroad. I'm still fairly likely to orient myself using the sun, and have also used paper city maps (they're easier to look at with another person, a point I should add to my answer to your other question). Compass-wise, you can often start moving and get the heading accurately from the GPS trace, if all you want is to pick the right road, but navigation can be far more interesting than that – Chris H Jul 20 '21 at 15:00
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    @ChrisH I simply find his comments disingenuous. It is a naked attempt at 'debating' in Stack Exchange. These questions are a vehicle to push his own narrative knowing full well how the community will react. We can all see that, we can see it clear as day, which is why the OP questions are broadly in the same area. And that is further evidenced by his 'Oh So Right' comment about smartphones which, being honest, is pure fantasy. This site is supposed to be for 'How do I do X' not for the OP to argue his technology fetish. – Venture2099 Jul 26 '21 at 18:24
  • ...it pained him to mark that answer as correct. He just wants to argue about phones. – Venture2099 Jul 26 '21 at 18:26
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    @Venture2099 having read of plenty of incidents caused by poor preparation and trusting technology, and witnessed some lucky escapes, I know people do go out hiking thinking as the OP does. Knowing that, I prefer to take such questions at face value; they're also of use to future readers if answered patiently – Chris H Jul 27 '21 at 06:32

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A phone app lacks many features that compasses have which are essential to orientation. Among the main ones:

  • A transparent casing that makes it possible to read the map through the compass and align the grid to the needle.
  • Numeric scales and rulers that enable you to make measurements on the paper map
  • (not on all models) Mirror with sight lines or reticles that enables you to sight landmarks and read the compass needle at the same time for more precise aiming
  • (not on all models) Mechanism to adjust dial for magnetic declination

Another quite important thing to know is that scattered around the world are magnetic anomalies, mostly ferromagnetic deposits. Considering electronic compasses drift pretty quickly and they need to be self-calibrated regularly, there is a chance that you could calibrate your electronic compass with a local bias, which would make it misaligned even when you left that area. This would not happen with a regular compass. The anomaly would skew the compass but it would return to normal afterwards.

Some anomalies are quite limited in range, but I've experienced a couple while sailing in the Caribbean that would disrupt the pedestal compass for at least a mile.

But more importantly, a phone will not work if the battery is dead. A compass will always work unless you accidentally demagnetize the needle.

Gabriel
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  • On your iphone 12 (and probably most phones) you can decide if you want it to adjust for magnetic declination or not in the settings – noah Jul 15 '21 at 20:46
  • @noah you're right! The phone compass becomes a lot more accurate if I enable "True North" in settings. thanks. – JonathanReez Jul 15 '21 at 20:55
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    Bear in mind, and I think I'll update my answer to reflect this, electronic compasses drift like crazy and they need to be self-calibrated regularly. Couple that with possible local magnetic anomalies, and you could skew the calibration significantly. – Gabriel Jul 16 '21 at 00:29
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    Apps can probably automatically adjust for magnetic declination using the phone's GNSS position, but you need to learn and practice how to apply the declination manually. In my area the bias is almost 20°W so if your phone is dead and you have not practiced how to account for this using the analog method, you're going to get off-course really quickly. – Gabriel Jul 16 '21 at 01:35
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    @Gabriel they might be able to use GNSS to address declination, but that either requires them to store declination data or download it on the fly. They may not have a signal, and I don't know if there's a suitable source of data anyway – Chris H Jul 16 '21 at 11:28
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    Enabling True North won't make it more accurate, but will make it match the map better. Perhaps that's a subtle distinction, but when you learn about magnetic declination it will become an important one. With how rarely I use my phone compass for anything significant, I end up calibrating it every time. – Chris H Jul 16 '21 at 11:35
  • @ChrisH Furthermore, the magnetic field drift model is revised every 5 years. Right now it's critical as the field is VERY active, so unless the app actively updates their data, the declination might not match reality perfectly. I updated last year the topo maps I produce with the updated model and it was about 1.5° off from the previous. – Gabriel Jul 16 '21 at 12:43
  • @Gabriel given the update rates that's a downside of paper maps (ours have the declination and rate of change printed on them but not the 2nd derivative; anyway calculating from that in the field would be tricky – Chris H Jul 16 '21 at 12:46
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    And the compass can be left in a pocket of your pack, so you will always have it and it will always work. – Jon Custer Jul 18 '21 at 15:12
  • BTW I probably wouldn't buy a sighting compass for most hiking/navigation. I have one, and it was very useful for Dartmoor Letterboxing which often relies on triangulation, but apart from that I've rarely used the mirror outside practice sessions; the extra precision isn't usually needed – Chris H Jul 20 '21 at 14:49