Xamarin Froms - how to tell if your phone compass is calibrated?

Question

Using Xamarin forms, how to determine if your compass is, or needs to be, calibrated? Yes, you can do compass calls to start and stop monitoring, but unless you know beforehand where North is, and see that the compass is not pointed to it... you do not know if you need to manually tilt and rotate the phone, to calibrate the compass. Is there any call to anything, to determine if compass is, or needs to be, calibrated?

Answer 1

Hello,

Welcome to our Microsoft Q&A platform!

Generally, mobile phone compasses are automatically calibrated. Usually we use Xamarin.Essentials: Compass to monitor the device's magnetic north heading. I check the source code of Xamarin.Essentials: Compass, and there is no method to calibrate the compass.

In iOS, calibrating is done at the OS level , you could guide the user to jump to the settings page to calibrate the compass. There is a CLLocationManager API and use locationManagerShouldDisplayHeadingCalibration(_:) to display the calibration alert.
Xamarin.Essentials: Compass has completed this function, you don't need to do additional operations if you use Xamarin.Essentials in your project, refer to https://github.com/xamarin/Essentials/blob/main/Xamarin.Essentials/Compass/Compass.ios.cs#L23

In Android, in rare instances, you maybe see inconsistent results because the sensors need to be calibrated, which involves moving your device in a figure-8 motion. The best way of doing this is to open Google Maps, tap on the dot for your location, and select Calibrate compass.

Xamarin provides full access to the underlying platform, so we could directly call the Android API and iOS API. You can find the .Net documentation for this at
https://learn.microsoft.com/en-us/dotnet/api/android.hardware.sensormanager?view=xamarin-android-sdk-12
https://learn.microsoft.com/en-us/dotnet/api/corelocation.cllocationmanager.shoulddisplayheadingcalibration?view=xamarin-ios-sdk-12

For example, in Xamarin.Android, you could customize a class to detect the sensor accuracy, refer to the following code:

public class CustomCompassClass : Java.Lang.Object, ISensorEventListener  
    {  
        public void OnAccuracyChanged(Sensor sensor, [GeneratedEnum] SensorStatus accuracy)  
        {  
            if (accuracy >= SensorStatus.AccuracyHigh)  
            {  
                //doesn't need to calibrate );  
            }  
            else  
            {  
                ///needs to calibrate  
                // you could pop up a message telling the user "Your android's compass needs to be calibrated. Please move the phone around in a horizontal figure eight motion until this message goes away."  
            }  
        }  
        public void OnSensorChanged(SensorEvent e)  
        {  
            throw new NotImplementedException();  
        }  
    }  

For more information, you could refer to
https://learn.microsoft.com/en-us/xamarin/essentials/compass?context=xamarin%2Fandroid&tabs=android

Best Regards,
Wenyan Zhang

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Answer 2

It wasn't a permission problem. I had put my dependencyservice calls in the MainPage.xaml.cs MainPage function (IsAvailable, and InitSensorService), ​just like the examples showed, but they never called OnAccuracyChanged. I also added another DependencyService call to
GetSensorAccuracy....

public MainPage()
{
InitializeComponent();
if (DependencyService.Get<ISensorEvent>().IsAvailable())
{
DependencyService.Get<ISensorEvent>().InitSensorService();

            SensorInformation.Text = "Sensor is available";
        }               
        else
        {
            SensorInformation.Text = "Sensor is NOT available";
        }
        SensorInformation.Text = DependencyService.Get<ISensorEvent>().GetSensorAccuracy();

    } #1

    protected override void OnAppearing() #2
    {
        base.OnAppearing();
        SensorInformation.Text = DependencyService.Get<ISensorEvent>().GetSensorAccuracy();

---

In the SensorEvent class I populated the variable AccuracyMessage and added the GetSensorAccuracy function...

public string AccuracyMessage;

public void OnAccuracyChanged(Sensor sensor, [GeneratedEnum] SensorStatus accuracy)
{
if (accuracy >= SensorStatus.AccuracyHigh)
{
AccuracyMessage = "Sensor Accuracy is High";
}
else
{
AccuracyMessage = "Your android's compass needs to be calibrated. Please move the phone around in a horizontal figure eight motion.";
///needs to calibrate
// you could pop up a message telling the user "Your android's compass needs to be calibrated. Please move the phone around in a horizontal figure eight" motion until this message goes away."
}
}

public string GetSensorAccuracy()
{
return AccuracyMessage;
}

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The OnAccuracyChanged function (which I never called directly, and was never accessed by my calls in the MainPage function), was called behind the scenes, between #1 (after leaving the MainPage function), and before #2 (OnAppearing), so I put the call to GetSensorAccuracy in the OnAppearing function...and thus did get the information as to the accuracy of the sensor.

The only question that I have left (sort of a sidetrack), is what do people think is more accurate, the phone compass sensor (Magnetometer ?), or a separate hand held compass?

Answer 3

Yes, I did get the calls to work. but at times, I could tell that the compass was not calibrated (even though the return message said that it was using high accuracy), and then, I did do the manual calibration.

No, it is not getting information that tells me if the compass is calibrated, it is getting information from the Magnetometer... "Magnetometers are for orientation sensing, not for position sensing".