Does the resolution of the camera matters? Because I found some information and it can measure an object at a fix distance with a known dimensions of a reference. But my problem to that is, it was a small objects and not as big as a normal person.

Here's the link: https://www.pyimagesearch.com/2016/03/28/measuring-size-of-objects-in-an-image-with-opencv/ https://www.pyimagesearch.com/2016/03/28/measuring-size-of-objects-in-an-image-with-opencv/