[Interest] Questions about QtSensors and QCompass

Lorn Potter lorn.potter at gmail.com
Wed Jan 6 23:50:26 CET 2016


Hi,

On 05/01/16 21:25, maitai wrote:
> Hello,
>
> I am trying to use QCompass sensor on Android and iOS.
>
> It works well on Android (didn't test on iOS yet), but I have questions
> regarding calibration:
>
> The link in qt documentation is dead (
> http://wiki.forum.qt.com/index.php/CS001671_-_Calibrating_the_magnetometer_sensor
> ). Does anyone knows where to find it or can explain how to proceed to
> calibrate the magnetometer? I tried to move the device in 8 figures and
> such but that does not seem to improve anything.
>
> I have two real devices. On the first one the north reported by the
> sensor is more or less ok, but on the second one it is completely false
> and not stable at all. Strangely both devices are reporting 0.0 as
> calibrationLevel... is it normal?

It really depends on the device and the android version. I have seen 
some versions of sensors on android that had only a proprietary 
calibration routine hidden for that specific device that was not hooked 
up to the usual calibration gesture and no automatic calibration.
I have also seen devices that take a long time to get calibrated (due to 
very (cheap) noisy magnetometers)

Then there is the issue with magnetic variance/deviation, and if it gets 
applied or not.

and on top of that, this all depends on local magnetic interferences 
like computers, metal objects and even components in the phone itself. :)

There are some android apps that will do compass calibration, but your 
mileage will vary on different devices.

Having a calibrationLevel of 0 or SENSOR_STATUS_UNRELIABLE means 
calibration is needed.

Hope this helps!

-
Lorn

>
> Thanks for any insight
> Philippe Lelong
>
>
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