iPhone compass app

Twister_Ken

Twister_Ken

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A word of caution should you ever think of navigating using the compass built in to your iPhone. A bunch of us were discussing how miraculous smartphones were. I mentioned the compass app. Four iPhones were produced - each showed a different compass heading. We made it as scientific as we possibly could, within the confines of a not very crowded bar, aligning the edge of each phone with the edge of a table. We still recorded a max difference of over 20º degrees between the two outlying bearings. Other people spotted what we were doing and joined in with their smartphones. Not one bearing was identical with another.

We speculated that there might be some anomaly, given that we were in a steel-framed building but it was too wet and cold to take the exercise outdoors. It would be interesting to know whether others have the same experience. These were iPhones - other smartphones are available!
 
My iPhone and iPad ....when removed from the case..agree with each other and appear to be correct but the iPad uses a different app. I've set them to True rather than magnetic. I guess they're good enough to use for when the sun goes in :)
 
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I use my iPhone 5, with OS maps installed, for winter mountain navigation. I've regularly checked the compass app against a normal silva/ suunto handbearing compass and found it consistently accurate. It usually requires calibration every now and again - what concerns me is that I don't know when or how it decides to recalibrate, and there's no obvious way to force a recalibration. Having that control would make me feel more comfortable about relying on the compass app. As it is, I tend to keep the handbearing compass to hand (but stored in a different pocket to avoid any influence from the magnets in the smartphone...)
 
ionbard said:
I use my iPhone 5, with OS maps installed, for winter mountain navigation. I've regularly checked the compass app against a normal silva/ suunto handbearing compass and found it consistently accurate. It usually requires calibration every now and again - what concerns me is that I don't know when or how it decides to recalibrate, and there's no obvious way to force a recalibration. Having that control would make me feel more comfortable about relying on the compass app. As it is, I tend to keep the handbearing compass to hand (but stored in a different pocket to avoid any influence from the magnets in the smartphone...)
Click to expand...

Having looked at some of the application notes published by Freescale [one of the makers of the sensor chips used in smartphones], my impression is that on start-up of a compass app it will ask you to wave the phone around to get enough calibration data. Once the app is running I think it is possible for it to keep updating the calibration data. Whether all the apps work that way, or some take some short-cuts is another question altogether.

Was that a metal table???
 
Metabarca said:
Clearly the first question to ask is whether they were all set to True (or Magnetic).
Having said that, I must say I've noticed an anomaly with the compass too.
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Variation now is so small, at least in the Solent, that I don't bother with the distinction. Under perfect conditions and under power my autopilot might be able to hold a course to 1 degree, but I know I can't. If my phone's compass was accurate to 5 degrees, I'd be happy as the only time I'd be likely to use it would be hiking, or in the flubber if fog came in suddenly. I doubt many folk could hold a course to better than 10 deg in those conditions.

As an aside, I was playing with a new satnav app (Here) and it complained that my compass had got confused. It wanted me to move the phone in a figure of eight pattern until the message disappeared. I did and it did. No idea how moving the phone in an 8 a foot wide could help it, but it seemed to.
 
Mine's always appeared accurate as far as I can tell, as well. Like others, I wonder whether all the phones on the table were calibrated, or affecting each other in some way? There are various augmented-reality apps which won't work properly without a compass accurate to at least a few degrees.

Pete
 
Stemar said:
As an aside, I was playing with a new satnav app (Here) and it complained that my compass had got confused. It wanted me to move the phone in a figure of eight pattern until the message disappeared. I did and it did. No idea how moving the phone in an 8 a foot wide could help it, but it seemed to.
Click to expand...

Steve, slight fred drift but what are you thoughts on the Here app?
 
I treated myself to an Autohelm Personal compass (the digital one) on the pretext that it would help me with my day job surveying. Quickly discovered that it was useless indoors, and not that great on any urban site.

Try walking around with a decent card compass indoors and you'll see that it wanders all around, and that height also has an initially surprising effect too.
 
Stemar said:
As an aside, I was playing with a new satnav app (Here) and it complained that my compass had got confused. It wanted me to move the phone in a figure of eight pattern until the message disappeared. I did and it did. No idea how moving the phone in an 8 a foot wide could help it, but it seemed to.
Click to expand...

Waving the phone about enables the app to get a set of magnetometer readings at different orientations, it can then do the sums to correct for the magnetometer calibration and local hard & soft iron disturbances. Similar thing to going around in a circle to correct a flux-gate compass on a boat.

Try this for a fuller description:-
http://cache.freescale.com/files/sensors/doc/app_note/AN4248.pdf
 
Giblets said:
Steve, slight fred drift but what are you thoughts on the Here app?
Click to expand...

I've only played with it briefly, but it found a couple of obscure streets in France that my current offline app (Offline Maps) struggled with. A couple of routes to places I know looked reasonable.

You can set it to put its offline maps on the card, saving main memory, but you have to do this in the setting before you start downloading. If you can spare the data, it will use online maps, but I use Waze in the UK. I mostly want it for France, where I'm far too tight to pay for data roaming.



It insists that my house number and street name is in a different postcode a few hundred yards away, but that's a fault with the mapping, as I've had many a call from a delivery driver insisting my house doesn't exist.
 
Twister_Ken said:
A word of caution should you ever think of navigating using the compass built in to your iPhone. A bunch of us were discussing how miraculous smartphones were. I mentioned the compass app. Four iPhones were produced - each showed a different compass heading. We made it as scientific as we possibly could, within the confines of a not very crowded bar, aligning the edge of each phone with the edge of a table. We still recorded a max difference of over 20º degrees between the two outlying bearings. Other people spotted what we were doing and joined in with their smartphones. Not one bearing was identical with another.

We speculated that there might be some anomaly, given that we were in a steel-framed building but it was too wet and cold to take the exercise outdoors. It would be interesting to know whether others have the same experience. These were iPhones - other smartphones are available!
Click to expand...

Four of us did the same thing and compared results with a 'proper' compass on a yachtmaster theory course, they were all over the place, even when we separated them by about a metre. We did learn that having them anywhere near the ships compass was not a good idea :ambivalence:
 
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