# ACCURACY MEASUREMENT: Spatial Calibration accuracy measurement

**URL:** <https://discourse.slicer.org/t/accuracy-measurement-spatial-calibration-accuracy-measurement/39746>\
**Category:** Support\
**Created:** [October 17, 2024, 1:38pm UTC](https://discourse.slicer.org/t/accuracy-measurement-spatial-calibration-accuracy-measurement/39746 "2024-10-17T13:38:50Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![jonortegav](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/jonortegav/32/78235_2.png) [@jonortegav](https://discourse.slicer.org/u/jonortegav)\
**Post date:** [October 17, 2024, 1:38pm UTC](https://discourse.slicer.org/t/accuracy-measurement-spatial-calibration-accuracy-measurement/39746/1 "2024-10-17T13:38:50Z")

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I have done the spatial calibration using a sequence recorded (using PLUS server launcher and 3D slicer sequence module) SlicerIGT Fiducial Registration Wizard module. The thing is that I have noticed that in the tutorial (U31 tutorial - slide 20) is mentioned the next (see figure):

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/4/d/4df80ab4067082bb0d84e5ebb954aef2256fdb8b.png)

The thing is that I obtained a RMS value of 37.7 but I don’t know how well the calibration has been made (as it says that "RMS increases but accuracy gets better).

I would like to know which is the RMS acceptable value range in order to know if a calibration is acceptable or needs to be done again.

Next image shows the result obtained from the spatial calibration:

 ![spatial calibration accuracy](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/0/5/0517533c74df41aa0bb3ff2186663c1b0a1bb17a.png)

Any help would be appreciated !

Thank you.

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**Author:** ![MReza](https://avatars.discourse-cdn.com/v4/letter/m/8baadc/32.png) [@MReza](https://discourse.slicer.org/u/MReza)\
**Post date:** [October 17, 2024, 4:12pm UTC](https://discourse.slicer.org/t/accuracy-measurement-spatial-calibration-accuracy-measurement/39746/2 "2024-10-17T16:12:12Z")

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Hello,

Based on my experience (always using a linear probe) and what I have observed from other researchers’ work, I would recommend that an error of less than 3 is acceptable.

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**Author:** ![jonortegav](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/jonortegav/32/78235_2.png) [@jonortegav](https://discourse.slicer.org/u/jonortegav)\
**Post date:** [October 21, 2024, 6:08am UTC](https://discourse.slicer.org/t/accuracy-measurement-spatial-calibration-accuracy-measurement/39746/3 "2024-10-21T06:08:31Z")

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Thank you very much @MReza !

Can anyone else confirm what @MReza has said please?