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I have been trying to calculate the compass heading using the magnetometer in an MPU9250 sensor. But the result is not making sense to me. I am completely new in this and do not have much understanding in how magnetometers work and just trying to find resources in the internet to make it work. I am calculating the `atan2` of the y and x axis readings of the sensor to find out the angle:

```
float mx = imu.mag_x_ut();
float my = imu.mag_y_ut();
float mz = imu.mag_z_ut();

float heading = atan2(my, mx) * 180 / PI;

Serial.print(mx);
Serial.print(",");
Serial.print(my);
Serial.print(",");
Serial.print(mz);
Serial.print(",");
Serial.println(heading);
```

My understanding is that when the `x` axis of my magnetometer faces the north direction the value of `heading` should be 0, for east 90, south 180 and then for west 270. But my calculations are nowhere near the expected results. I am not even getting a zero reading in any directon. I am attaching the screenshots of the direction reading :

This is when x axis points to north.
[![x pointed to north][1]][1]

Rotated x axis towards east.
[![x pointed to east][2]][2]

x towards south.
[![x pointed to south][3]][3]

x towards west.
[![x pointed to west][4]][4]

I have also added the raw readings from the magnetometer represnted by `mx`, `my` and `mz`. Is something wrong with my sensor or there is some misunderstanding from my part. 

EDIT: Readings after hard iron offset compensation.

[![after hard iron offset][5]][5]


 [1]: https://i.sstatic.net/BWiup.png
 [2]: https://i.sstatic.net/YybqS.png
 [3]: https://i.sstatic.net/98QSn.png
 [4]: https://i.sstatic.net/72d62.png
 [5]: https://i.sstatic.net/W8jot.png

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