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Real accuracy of calibration?

asked 2015-04-09 18:04:19 -0600

palumbs gravatar image

I'd like to know something about the accuracy of the calibration process, even if the results have several decimal places, i'm not sure that its accuracy is really that.

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answered 2015-04-10 01:01:52 -0600

updated 2015-04-10 02:15:42 -0600

One important measure is the reprojection error of your calibration targets. If you do a standard calibration, you get the internal camera matrix and the relative pose for all targets to the camera. You can then use this information to project all patterns into your images and check if the projected point is close to its former detection. (the rmse of theses pixel distances is also the return value of calibrateCamera)

A good calibration is well below 1 px as a rule of thumb.

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yes, thank you for your answer, but i'd like to know if the accuracy on fx,fy,cx,cy is really to the 16th decimal place or not.

palumbs gravatar imagepalumbs ( 2015-04-10 03:44:41 -0600 )edit

No. That will be just random noise. You could take your set of calbration images and run the calibration several times on subsets of these images. (e.g. always remove one image and run the calibration on the other N-1 images). You should get rather similar values for fx that will diverge after some decimals. That approach could give you a first insight in how many decimals are important.

FooBar gravatar imageFooBar ( 2015-04-10 03:57:55 -0600 )edit

good idea thank you.

palumbs gravatar imagepalumbs ( 2015-04-10 05:18:11 -0600 )edit

Could you report your findings here after you've done the experiment? It's an interesting question and I'm especially interested in the different distortion parameters.

FooBar gravatar imageFooBar ( 2015-04-10 05:57:31 -0600 )edit

yes, no problem. Some minutes ago i asked something else about the radial distortion parameter K2, take a look at that if you can help me.

palumbs gravatar imagepalumbs ( 2015-04-10 06:20:11 -0600 )edit

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Asked: 2015-04-09 18:04:19 -0600

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Last updated: Apr 10 '15