When we consturct the 3D coordinates of the checkerboard corners, does the unit of length matter?

I have read multiple articles and example codes for camera calibration with OpenCV. To represent the 3D coordinates on a checkerboard, some use centimeter as a unit, some use meter as a unit, some simply consider the length of one checkerboard box as 1 without any unit of length involved.

So how is the length of unit determined when we calibrate a camera?

CodePudding user response：

It is up to you to decide whether to treat the length of 1 meter as {1m, 100cm, 1000mm, etc.}. All you have to do is decide based on what kind of unit system the program should operate on.

For example, if you want to estimate the height of a person from a camera image, you could do the calculation using nm(:nanometer) as the unit of length, but that would be silly. You may use different units.

CodePudding user response：

Without a priori knowledge of the world, there is a fundamental world scale ambiguity in monocular camera pose estimation and SLAM. However if the checkerboard is a known physical reference object, then you can set the scale accordingly that way.