If you bought the cheap magnetomter module like HMC5883L you can not use it without calibration. Measurement of magnetic field will be subjected to distortion. There are two categories of these distortions: the hard iron distortions and the soft iron distortions. The hard iron errors refer to the presence of magnetic fields around the sensor (magnets, power supply wires) and are related to measurement offset errors, while the soft iron errors refer to the presence of ferromagnetic materials around the sensor, which skew the density of the Earth's magnetic field locally and are related to scaling offset errors. You can read more information about these distortions here.

In other words, to get the correct magnetometer data you should get the calibrated magnetometer data. One of the ways to resolve this problem: you should apply the bias to the vector of the non calibrated magnetometer data (X, Y, Z coordinates) and then multiply the transformation matrix by this resulting vector:

3689598033?profile=originalPicture 1

In this case the magnetometer calibration is the process of getting the transformation matrix and the bias. To get these data you can use the MagMaster program.

You can download MagMaster here.

Example of using the MagMaster



  • MagMaster (placed in MagMaster folder)
  • MagViewer (placed in MagMaster folder)


  • Arduino Sketch (placed in MagMaster folder)

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3689598042?profile=originalPicture 3

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Connect the magnetometer module to the arduino board via I2C bus (picture 4). Upload the arduino sketch to the arduino board (see "Arduino_Code" folder in the "MagMaster" folder). This arduino sketch requires the HMC5883L library, copy the folder "HMC5883L" (placed in "Arduino_Code" folder)  to the folder "C:\Program Files\Arduino\libraries".

Then run the MagViewer.exe, select the serial port of the arduino board (the boud rate of the seraial port should be 9600 bps) and click "Run MagViewer". Now you can see the coordinates of the magnetometer data vector in 3D space on a real time (picture 5, video 1, 2). These data are not calibrated yet.

3689597980?profile=originalPicture 5

Video 1

Video 2

If you see the points of the magnetometer vector coordinates in 3D space the arduino board and the PC connection works right.

Now close the MagViewer window and run the MagMaster.exe (picture 6). Select the serial port of the arduino board. The green strings X, Y, Z will indicates the coordinates of the magnetometer vector.

3689598100?profile=originalPicture 6

Place the magnetometer module as shown on the picture 8.1 and click "Point 0" button of the "Axis X+" groupbox. For the placement of the module you can use the wooden bar or the paper box (picture 7). If you can not connect your magnetometer device to PC then you can use any other way to get to know the magnetometer data. You can enter these data in the program manually.

3689598052?profile=originalPicture 7

Place the magnetometer as shown on the picture 8.2 and click "Point 180" button of the "Axis X+" groupbox and so on. You should do in the following way:

  • Picture 8.1: "Point 0", "Axis X+"
  • Picture 8.2: "Point 180", "Axis X+"
  • Picture 8.3: "Point 0", "Axis X-"
  • Picture 8.4: "Point 180", "Axis X-"
  • Picture 8.5: "Point 0", "Axis Y+"
  • Picture 8.6: "Point 180", "Axis Y+"
  • Picture 8.7: "Point 0", "Axis Y-"
  • Picture 8.8: "Point 180", "Axis Y-"
  • Picture 8.9: "Point 0", "Axis Z+"
  • Picture 8.10: "Point 180", "Axis Z+"
  • Picture 8.11: "Point 0", "Axis Z-"
  • Picture 8.12: "Point 180", "Axis Z-"

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You should fill the table. After that click "Calculate Transformation Matrix and Bias" and get the required matrix and bias (picture 9).

3689598116?profile=originalPicture 9

The transformation matrix and the bias are got. Now you can calculate the calibrated magnetometer data in your device on a real time with using the matrix and the bias as shown on picture 1. The example of the arduino sketch of using this calculation you can find in the "Arduino_Test_Results" folder.

You can apply the sphere radius stabilization algorithm to your program (use for it the Arduino_Radius_Stabilization folder placed in MagMaster folder).

The calibrated magnetometer vector coordinates in 3D space with the radius stabilization shown on the picture 10 and video 3, 4.

3689598230?profile=originalPicture 10

Video 3

Video 4

Using of the arduino is only example, you can easy adopt the arduino code for any other system and use the MagMaster program with it.

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  • I really did not understand, how to place the magnetometer (in-spite of you providing lot of diagrams) for it's calibration. My first question is that,  do i need to know the exact directions (N,E,W,S), before beginning calibration?

    From 12 diagrams that you have provided, i understood that the the box is not stationary. what about the magnetometer? How exactly the magneto meter must be placed over the box? what exactly must be its orientation?

    Please do reply. 

  • I cant get either program to connect to the Serial port.  Whenever I try to connect, the program crashes.  I tried both MagMaster & MagViewer, both with the same results.  Ive made sure all my settings are correct.  9600 baud, "val1,val2,val3" + CR for each sentence.  I even removed the spaces after the comma's thinking that might fix it.

  • Hello Rainer W.

    I have no time for correct MagMaster and MagViewer now. You can do it yourself, here is the source code of MagMaster https://github.com/YuriMat/MagMasterSource/archive/master.zip. This is Visual Studio 2010 C# project (sorry for not very optimised code). If you need MagViewer source code then I will share this code later.

  • Hi Yury,

    I discoverd your nicely looking MagMaster and intended to use it with a HMC5883 connected to an arduino pro micro. But unfortunately the pro micro needs a signal on the DTR handshake line to enable serial output. I checked with HTerm and can receive data like "400.00,28.00,-928.00<cr><lf>" while the DTR line is activate. Perhaps it is possible to add a toogle button to MagMaster and MagViewer to control the DTR line of the serial port. Thanks for the great software.

  • I used your Magmaster method to calibrate the magnetometer modul HMC5883L. Could you help me to check my calibrate result,correct or incorrect based on this picture3701823717?profile=original

  • alejandro,

    for this rotate the magnetometer around axis ortogonal to the earth plane.

  • hello, how i do the ring in magviewer

  • Michael,

    and your results on the picture is incorret.

  • Michael,

    Try to read my comments for Harry above. Harry posted his first comment on June 28, 2014 at 5:24pm. I thinks your problem it is the same.

  • Hi Yury,

    I followed your instructions and ran the calibration with the following results. I'm very new so I'm not sure if anything looks wrong in my results. Can you confirm my results? Please let me know if I need to re-do this test.

    Kindest regards,



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