It's true that many types of velocity measurements are going to include some position information. The uncertainty principle says that the position information will limit the precision of the velocity determination. A nice example of this is the "diffraction limit" of the human eye. To know which direction the light is coming from, you must have that light pass through your pupil. So you might ask, how can I know what direction it is coming from (I know its speed is c), if I also have to know that it passed through the location of my pupil? The answer is, if it passes through your pupil, then that position knowledge does limit how well you can know the direction-- that's diffraction in a nutshell.