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  1. #1
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    Algorithm to calibrate Magnetometer in Sensor API

    Does anyone know how to change raw data of Magnetometer in calibrated data?
    Or how the calibration of Magnetometer in Sensor API works?
    I have a N97 and I know that in order to calibrate its compass I need to move it around but I need to know what really happens there (how the algorithm works or how it was implemented).

    Thank you!

  2. #2
    Super Contributor
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    Re: Algorithm to calibrate Magnetometer in Sensor API

    Quote Originally Posted by luckystar05 View Post
    Does anyone know how to change raw data of Magnetometer in calibrated data?
    Or how the calibration of Magnetometer in Sensor API works?
    I have a N97 and I know that in order to calibrate its compass I need to move it around but I need to know what really happens there (how the algorithm works or how it was implemented).

    Thank you!
    How it has been implemented is Nokia's internal stuff. What we can know is how to calibrate it and how to use it.
    There is an example in wiki http://wiki.forum.nokia.com/index.ph...gnetic_Compass
    you can take a look in it.

    About calibration there is some code examples that can be consulted and that can be found in from this link.

  3. #3
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    Re: Algorithm to calibrate Magnetometer in Sensor API

    Thank you Mahbub!
    Actually I have searched through the Nokia Library before and coundn't find the thing I need.

  4. #4
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    Re: Algorithm to calibrate Magnetometer in Sensor API

    Did you get what you need now?

  5. #5
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    Re: Algorithm to calibrate Magnetometer in Sensor API

    No, I didn't.

  6. #6
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    Re: Algorithm to calibrate Magnetometer in Sensor API

    Hi,
    Could you mention what else you need to solve your problems?

  7. #7
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    Re: Algorithm to calibrate Magnetometer in Sensor API

    I think I need nothing other than the way to calibrate raw data, because I have to calculate the azimuth from raw data.

  8. #8
    Nokia Developer Moderator
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    Tampere, Finland
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    Re: Algorithm to calibrate Magnetometer in Sensor API

    A Google search for "magnetometer sensor calibration" returns an interesting PDF as first link, which not only makes a review of known calibration methods (with refernces for mode info), including "the classic compass swinging calibration technique", but also proposes a new algorithm for solving the problem. See A Geometric Approach to Strapdown Magnetometer Calibration in Sensor Frame. I'm sure it will be a good read.

    As for the algorithm used in the Sensor Framework, you can have a look at the source code and see what you can learn out of it. The advantage of open source.

    However, it is my understanding that the reason for all this effort in calibrating the sensor is to improve the accuracy. Otherwise, the uncalibrated data would be as useful to you as a random choice of direction.
    -- Lucian

    If you are not yet a DVLUP member it is time to correct that mistake :) Click here to join: http://www.dvlup.com/lucian/Invite

  9. #9
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    Re: Algorithm to calibrate Magnetometer in Sensor API

    Thank you, Lucian!
    The document is very helpful!

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