Hello guys. I am quite familiar with magnetic measurements, compasses in general. There is a glaring elephant in the room when it comes to using these sensors on a phone.
If a phone case or pouch has a magnetic clasp, which many do, the magnets used will nearly always put the sensors well out of calibration. This can render them incapable of indicating North and get stuck in the wrong direction. They can easily be recalibrated, by moving the phone at arms length in a wide figure of right pattern. However simply closing a case or replacing into a pouch can loose cal again. Currently my phone, a Pixel 2 indicates North in any direction ! For reference earth's magnetic field in the UK is about 45μT. It varies around the world getting as high as 60 in certain places. Currently my phone has a total field measurement of 168μT, hugely too high, caused mainly by one sensor, the Bz. The earth's field is given by H = square root(Bx^2+By^2+Bz^2) Not sure what Maps does regarding calibration, although it's possible it could handle the sensor data as is and make sense of it. Bottom line remove suspect cases and recalibrate Hope this is useful. Ken On Sat, 25 Jun 2022, 17:28 Peter B - pebogufi, <[email protected]> wrote: > Two more tools to read hardware info: > + Droid Hardware Info / InkWired > + phyphox / RWTH Aachen University > > [email protected] schrieb am Samstag, 25. Juni 2022 um 15:41:23 UTC+2: > >> Hi Greg, thank you! I installed SatStat on my old phone, and the Bx By Bz >> values vary when I change the orientation of the phone, and they are >> completely different to the values on my new one. >> >> I give up. Nevertheless many thanks! >> >> Greg Troxel schrieb am Samstag, 25. Juni 2022 um 15:10:12 UTC+2: >> >>> >>> Clemens Jensen <[email protected]> writes: >>> >>> > I can't interpret the Bx By Bz values. SatStat shows this (pic 1 phone >>> > directed to North, pic 2 to East, pic 3 to South, pic 4 to West): >>> >>> They are the three components of the magnetic field. That's what the >>> phone actually measures and from that computes an orientation. I have >>> no idea where you are, and don't even know the values around me. My >>> point is that with two phones, I think you should be seeing similar >>> values. By taking two of them outside away from metal, and orienting >>> them the same, and seeing the values, and then repeating, you should be >>> able to gain some insight into whether the problem is the raw >>> measurements, or something later in the processing chain. >>> >>> In your case, with the suspect phone, it looks like all 4 positions have >>> similar Bx/By/Bz values. Mine change as I rotate, but not in a way >>> that's easy to understand. >>> >> -- > You received this message because you are subscribed to the Google Groups > "OsmAnd" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/osmand/9b93ee04-ff71-4e78-bd1d-f1f703a2e470n%40googlegroups.com > <https://groups.google.com/d/msgid/osmand/9b93ee04-ff71-4e78-bd1d-f1f703a2e470n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "OsmAnd" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/osmand/CAMt6mLRz42Ecynog-qRLeHPVKq9pwr83CzPy5jZmmyxyOUtn5g%40mail.gmail.com.
