Image Lucas-Kanade Optical Flow

Question

I am new to this optical flow in image space, and I am kind of confused that weather the optical flow computed in OpenCV by Lucas-Kanade method is distance, displacement or velocity. Perhaps I might sound foolish but I am really confused.

I feel its velocity but I just want to confirm?

Answer 1

I assume you refer to opencv function calcOpticalFlowPyrLK.
This function tracks the position of interest points found in old-frame and returns their position at the new-frame.

Answer 2

The Lucas-Kanade method estimates the local image flow (velocity) vector at point p.

Answer 3

This method computes the displacement of some interest points between two sucessive frames. The output vector contains the calculated new positions of input features in the second image as it is stated in the following link in documentation as well : http://docs.opencv.org/2.4/modules/video/doc/motion_analysis_and_object_tracking.html