Magnetic Declination in IMU filter

Question

Mohammad Reza Ramezani 2020-9-9

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https://ww2.mathworks.cn/matlabcentral/answers/591106-magnetic-declination-in-imu-filter

评论： William Rose 2023-9-13

Hi.

I'm new to Matlab. I'm using imu filter and mpu9250(based on Matlab example) to calculate pitch, roll, and yaw. but i don't know if the imu filter considers the magnetic declination in its calculation or not, and if not how can I correct my data?

thanks for helping me

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Carla 2023-9-13

Hi Mohammad, I am dealing with the same issue. Have the pitch and roll corrected but still have to aply the magnetic declination correction to the yaw. Did you figure out how to aply this correction? I would be very thankful:)

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Answer 1

William Rose 2023-9-13

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@Mohammad Reza Ramezani,

I am confident that the algorithm does not account for magnetic declination. We called it compass variation when I worked as a navigator. I say that because the ony way the algorithm could take it into account is if it knows the lat,long of the observer's location - and it does not. YOu could even say that it would have to know the year of the observation, since magnetic declination changes slightly from year to year.

To address the issue, you will have to correct using a table and 2D interpolaiton, or call one of the online declination sites such as here.

Good luck!

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William Rose 2023-9-13

Since you are using the mpu9250, I assume you are navigating across a span of meters or a few km, and you are not navigating across hundreds of km. Therefore you can apply a constant correction. You can look up the correction for your location here. Example: If you are in Cape May, New Jersey (the location of the compass rose shown in my answer above), the variation in 2023 is -11.89 degrees. The old chart image above shows that the variation was -12.15 d in 2004. See screenshot below: