What is the difference between image error and object error in fiducial transforms?

[sebymv]

I am using fiducial transforms for finding the transformation between camera and object for camera calibration. I published the topic /fiducial_transforms which publishes image error and object error along with rotation and translation. I would like to know what exactly is image error and object error

`fiducial_id: 100
transform:
translation:
x: 0.138788760176
y: -0.0747502797036
z: 0.53854969072
rotation:
x: -0.70370667908
y: -0.67279283292
z: 0.194322848383
w: 0.119938919401

image_error: 5.73826072874

object_error: 0.0989452949008

fiducial_area: 25640.8290787
`

[MoscowskyAnton]

I also wonder that, have some ideas here #213
From source code I figure out that image_error is reprojection error in pixel, and object is the same, but converted to meters, based on aruco side length.