Markers' mean error diverges

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orita
Posts: 3
Joined: Mon Jan 27, 2020 4:34 am

Markers' mean error diverges

Post by orita » Mon Jan 27, 2020 6:15 am

Hello all,

I use OptiTrack FLEX 13 cameras and rigid bodies with 4 reflective markers on each one of the bodies.
I saw that the markers' mean error starts at 0.01 mm/marker and goes up and up as time goes by (attached 'capture1')
even when (I think) I well spreaded the markers (attached 'capture2')
It causes bad path tracking control.

how to solve that?
Is there a recommendation for minimal distance between the markers? and is it possible to use only 3 markers for each rigid body?


Thank you very much
Orit
Attachments
Capture2.PNG
Capture2.PNG (1.43 KiB) Viewed 169 times
Capture1.PNG
Capture1.PNG (10.12 KiB) Viewed 169 times

steven.andrews
NaturalPoint Employee
NaturalPoint Employee
Posts: 548
Joined: Mon Jan 19, 2015 11:52 am

Re: Markers' mean error diverges

Post by steven.andrews » Mon Jan 27, 2020 1:13 pm

Hello Orit,

Thank you for reaching out to the community regarding your rigid body tracking.
If the mean marker error is slowly increasing, this could be due to loss in your overall system calibration. This would cause noisier marker data, which would likely cause an increase in the mean marker error.

You can view the system's residual in the Status Panel. If this is low right after calibration, and then higher later on, this means the calibration is degrading. This is usually due to environmental factors, such as temperature fluctuation or vibrations on the camera mounts.

You can use three markers for a rigid body, but this does not leave any redundancy and the rigid body can stop tracking if a single marker is occluded. Using 4 markers versus 3 should not cause the marker error to get worse with time.

If you continue to struggle with this, feel free to reach out to our Support team directly.

Best regards,
Steven
--
Steven Andrews
OptiTrack | Senior Customer Support Engineer
help.naturalpoint.com
support@optitrack.com

orita
Posts: 3
Joined: Mon Jan 27, 2020 4:34 am

Re: Markers' mean error diverges

Post by orita » Tue Feb 04, 2020 2:57 am

Hello Steven,

Thank you very much for the reply.

I use 1.7.5 Motive and I can't find the control panel.
When I click the bottom right corner, a control log pops up (attached)
I dont have the Residual there.

Will appriciate your help
Orit
Attachments
Capture5.PNG
Capture5.PNG (25.88 KiB) Viewed 133 times

steven.andrews
NaturalPoint Employee
NaturalPoint Employee
Posts: 548
Joined: Mon Jan 19, 2015 11:52 am

Re: Markers' mean error diverges

Post by steven.andrews » Tue Feb 04, 2020 11:25 am

Thanks Orita,

Motive 1.7.5 is quite old, and not something that was well documented. The status panel does not exist in that version, but I believe the residual may display somewhere at the bottom of Motive. If not, I am not sure where to find the information we are looking for.

Best,
Steven
--
Steven Andrews
OptiTrack | Senior Customer Support Engineer
help.naturalpoint.com
support@optitrack.com

orita
Posts: 3
Joined: Mon Jan 27, 2020 4:34 am

Re: Markers' mean error diverges

Post by orita » Wed Feb 05, 2020 11:22 am

thanks for the response.

another question,
what is the best markers configuration?
how do I know the markers were well spreaded?
do I want maximum overlap or not overlap at all? I attached a few examples


Thank you in advance
Orit
Attachments
mrkr3.PNG
mrkr3.PNG (1.37 KiB) Viewed 124 times
mrkr2.PNG
mrkr2.PNG (1.32 KiB) Viewed 124 times
mrkr1.PNG
mrkr1.PNG (1.27 KiB) Viewed 124 times

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