Understanding Internal Camera Parameters

PIX4Dmapper
1

I’ve been working my way through the documentation about how to understand the Quality Report.

I’ve learned what the parameters are depicted on the Internal Camera Parameters section (thanks to google) but I don’t understand what the values on the Quality Report are telling me.

I suspect this section is providing information on how well my camera is making images. Is there a reference I can use that tells me if my values are OK?

internal camera parameters
internal camera parameters985×816 78.5 KB

2

hi @joe.stroup

You can find additional information here:

If you are using a camera with a perspective lens, keep in mind that:

the principal point should be around half the resolution of the camera, and that the radial distortion values R1, R2, R3 should each be smaller than 1. The uncertainties on the focal length and the principal point should be only a few pixels. The uncertainties on the distortion parameters should be close to zero. For more information about how to edit the initial camera parameters: How to use the Editing Camera Model Options.

3

Hello Daniele -

Thanks for replying. Unfortunately, your response isn’t helpful. I had read the docs you mention. They identify the items on the quality report - but offer little to explain what they mean and how to evaluate them.

I was hoping you might be able to shed some light on that. Perhaps by referring me to a link that has that information.

Regards - Joe Stroup

4

Hello @joe.stroup, The easiest way to interpret the above graph and the table is by making sure that the Optimized values are almost the same as the original camera parameter. The graphic is showing the correlation between the parameters of the camera. The highest quality calibration is characterized by decorrelated parameters. However, having some type of correlation between parameters is sometimes expected:

  • In projects with nadir images, a correlation between the radial distortion parameters and between the coordinates of the principal point is expected.
  • In close-range projects with oblique images, a correlation between the focal length and the coordinates of the principal point is expected as well as between the coordinates of the principal point and the tangential distortions.

So, the graphic with black and white boxes is the normal graph(as in your case). If you see the graphic with all the black boxes which indicates all the parameters are independent then it is not normal or the parameter are not good.

5

Many thanks Kapil - that’s very helpful.