Re: Compass calibration of Vector

Hi,

I will be deploying Vector on a mooring line with a vane and an external battery case attached to the vane in a week.  I performed the compass calibration of Vector mounted on a vane with external battery case.  The result is attached.  I tried the compass calibration several times and "estimated maximum error after calibration" varies from 1 deg to 8 deg.  I chose to use the minimum error value of 1 deg to update instrument, but I am not sure why the results differ so much.  Is there a reference value I can use to tell whether I perform the calibration successfully?  What does each value (dX, dY, K[1,1], K[2,2], Mx, My, Mz, Heading, Pitch, Roll ) represent?

Mei

Dear Mei Sato,

It is very important to do the rotation slowly - particulary around the extremal values in both axis. I think this is the reason of the different results.

What we try to do with this calibration is to make a calculation matrix such that the result of the rotation around the z-axis gives a round circle around origo. If we're successful in this the instrument experience the same magnetic field regardless of were it is pointing.

The validation test is basically to spin it around the z-axis and see that the circle is round and centered in origo.

dX - is the offset in the x-axis which we subtract when calculationg the heading

dY - is the offset in the y-axis which we subtract when calculationg the heading

K[1,1] - Scaling factor for the x-axis to make Xmax-Xmin equal to Ymax-Ymin

K[2,2] - Scaling factor for the y-axis to make Xmax-Xmin equal to Ymax-Ymin

Heading - the orientation of the instruments x-axis 0 deg corresponds to north

Pitch and roll - the instruments angles from the horizontal plane see attached picture

Best regards

Jonas Røstad

Hi Johnas,

Thanks for the explanation.  The figure I attached yesterday was the one I did slow rotation and gives me the lowest maximum error.  To clarify, do you think the result I attached was good enough as a calibration and successful?

Mei

Hi Johnas,

Thanks for the explanation.  The figure I attached yesterday was the one I did slow rotation and gives me the lowest maximum error.  To clarify, do you think the result I attached was good enough as a calibration and successful?

Mei

Hi Mei,

The attached reult seems to be a good one.

Good luck with your deployment.

Best regards

Jonas