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Comment by arcastroe | Hacker News Reader

Does everyone's phone compass just work reliably? For me, it seems like the most unreliable part of navigation. I traveled to Italy recently and heavily used Google Maps with walking directions, and it was frustrating the number of times I started walking in the wrong direction, due to the compass saying I was facing a direction I wasnt.

If this device uses a similar technology as your phone, then I don't see it being reliable.

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The magnetic sensor in your phone is actually pretty weak and requires regular calibration to pick out the true magnetic field lines from all the noise.

Your phone has many magnets inside, and structures that can be passively magnetized. Your local magnetic environment changes constantly.

It's a fundamental limitation of the technology, unfortunately. Generally we use GPS location as you move to infer direction and feed that back into the compass routines. It's not great but it does mostly work sometimes

Have you done orienting in the past?

One of the big tricks is to realize that magnetic north (where your compass points) is usually not the same as geographic north (where maps are drawn). The adjustment is local; here, I think magnetic north is 7 degrees off from north.

In the US, the USGS topographic maps contain the required adjustment for the covered area. Not sure about Italy.

I don't think that's it. For me sometimes my phone compass is (roughly) right, but sometimes points in a completely wrong direction, for example 90 degrees off. It calibrates after a while when I start walking but I guess this is what OP had in mind, not a few degree difference.

iPhones can regain the compass fix if you move the phone along a figure eight path while holding it flat and level. Worked pretty well for me in the past.

I'm fairly often doing figure-8 with my phone in front of myself to realign the compass.

Thoughtful concept but agreed. I.i.r.c the phone can assess the inaccuracy of the compass and prompt the figure-8 movement. But that is not practical here.

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