About the Hard and Soft-Iron Calibration

[ijunglee]

Hello, I have read the hard-iron and soft-iron magnetic field calibration in your Wiki 'Simple and Effective Magnetometer Calibration':

// Get hard iron correction
mag_bias[0] = (mag_max[0] + mag_min[0])/2; // get average x mag bias in counts
mag_bias[1] = (mag_max[1] + mag_min[1])/2; // get average y mag bias in counts
mag_bias[2] = (mag_max[2] + mag_min[2])/2; // get average z mag bias in counts

dest1[0] = (float) mag_bias[0]_MPU9250mRes_MPU9250magCalibration[0]; // save mag biases in G for main program
dest1[1] = (float) mag_bias[1]_MPU9250mRes_MPU9250magCalibration[1];
dest1[2] = (float) mag_bias[2]_MPU9250mRes_MPU9250magCalibration[2];

// Get soft iron correction estimate
mag_scale[0] = (mag_max[0] - mag_min[0])/2; // get average x axis max chord length in counts
mag_scale[1] = (mag_max[1] - mag_min[1])/2; // get average y axis max chord length in counts
mag_scale[2] = (mag_max[2] - mag_min[2])/2; // get average z axis max chord length in counts

float avg_rad = mag_scale[0] + mag_scale[1] + mag_scale[2];
avg_rad /= 3.0;

dest2[0] = avg_rad/((float)mag_scale[0]);
dest2[1] = avg_rad/((float)mag_scale[1]);
dest2[2] = avg_rad/((float)mag_scale[2]);

I would like to ask that what are the array dest1 and dest2?
Does this mean that I have to substrate the original mag data with the dest1 for hard-iron calibration? How about dest2?
Thanks in advance!

[kriswiner]

Take a look here for how these are used:

https://github.com/kriswiner/MPU-9250/blob/master/MPU9250_MS5637_AHRS_t3.ino

-----Original Message-----
From: ijunglee [mailto:notifications@github.com]
Sent: August 25, 2016 5:39 AM
To: kriswiner/MPU-6050
Subject: [kriswiner/MPU-6050] About the Soft-Iron Calibration (#14)

Hello, I have read the hard-iron and soft-iron magnetic field calibration in
your Wiki 'Simple and Effective Magnetometer Calibration':
`// Get hard iron correction
mag_bias[0] = (mag_max[0] + mag_min[0])/2; // get average x mag bias in
counts
mag_bias[1] = (mag_max[1] + mag_min[1])/2; // get average y mag bias in
counts
mag_bias[2] = (mag_max[2] + mag_min[2])/2; // get average z mag bias in
counts

dest1[0] = (float) mag_bias[0]MPU9250mResMPU9250magCalibration[0]; // save
mag biases in G for main program
dest1[1] = (float) mag_bias[1]MPU9250mResMPU9250magCalibration[1];

dest1[2] = (float) mag_bias[2]MPU9250mResMPU9250magCalibration[2];

// Get soft iron correction estimate
mag_scale[0] = (mag_max[0] - mag_min[0])/2; // get average x axis max chord
length in counts
mag_scale[1] = (mag_max[1] - mag_min[1])/2; // get average y axis max chord
length in counts
mag_scale[2] = (mag_max[2] - mag_min[2])/2; // get average z axis max chord
length in counts

float avg_rad = mag_scale[0] + mag_scale[1] + mag_scale[2];
avg_rad /= 3.0;

dest2[0] = avg_rad/((float)mag_scale[0]);
dest2[1] = avg_rad/((float)mag_scale[1]);
dest2[2] = avg_rad/((float)mag_scale[2]);`

I would like to ask that what is the array dest1 and dest2?
Does this mean that I have to substrate the original mag data with the dest1
for hard-iron calibration? How about dest2?
Thanks in advance!

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[ijunglee]

Thank you. I have see that and have other questions of the code. I have posted the questions on the issue.