Problems with accuracy

[sdorman]

I've followed the tutorial to set up Whycon. I've run set_axis and calibrated the camera using the monocular camera calibration tutorial each time. I changed the circle_detector.h file to have the correct size of my targets. But my z distances are inaccurate compared to physically measuring the distance with a tape measure.
I've tried different size targets, different size calibration boards, different number of targets, different distances between the camera and targets. I still have errors up to 20 cm in the z axis. I'm not sure what else I can do. Any help would be appreciated.