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Author Topic: Markers eroors before and after selection  (Read 1340 times)

Damian

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Markers eroors before and after selection
« on: May 28, 2020, 10:40:15 AM »
Hello!
The question is about the error [m] value of markers. We have three situations:
1. All markers are selected and the cameras are optimized on them - error on control points is 0,0014 m. (1st attachement - selected_optimized)
2. I unselect all markers - the error on check points raises to 0,0037 mdespite the fact, that i have not optimised the cameras yet. (2nd attachement - unselected_before_optimization)
3. I optimize the camaeras and the error on check points is 0,187 m. (3rd attachement - unselected_optimized)

I understand the change of value between optimisation on selected and deselected markers. I don't understand why there is a value change after deselection and before the optimisation.

Loking forward to reading some explanation.

Alexey Pasumansky

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Re: Markers eroors before and after selection
« Reply #1 on: May 28, 2020, 05:57:31 PM »
Hello Damian,

Please see my post regarding the difference of the error estimation for Control and Check points in another thread:
https://www.agisoft.com/forum/index.php?topic=11329.msg50857#msg50857

Quote
In Metashape Pro (and PhotoScan Pro) versions prior to 1.5.4 estimated control point coordinates displayed in the Reference pane (and the error values as well) were calculated based on minimization of the reprojection error only, without taking into account measured control point coordinates in space. So they did not correspond to adjusted coordinates from the bundle adjustment step, and were recalculated from weighted image measurements alone.
 
Starting from Metashape Pro version 1.5.4 estimated control point coordinates correspond to the adjusted values, that is, they are calculated taking into account both reprojection error and measured object space coordinates. Similar behavior is common for other software packages and also allows for better detection of the measurement errors.

If you are interested in the difference between measured and triangulated control point coordinates, you can temporary uncheck the corresponding entry in the reference pane (thus making it a check point). Please note that check point error calculation is not affected by the change mentioned above. Upon unchecking the control points you do not have to click on Update button.
Best regards,
Alexey Pasumansky,
Agisoft LLC