15.5.3 Velocity Measurements
Another commonly studied parameter in time-lapse imaging experiments is
velocity [44, 47, 51]. It is computed simply as distance over time. Instantaneous
object velocity can be estimated as the distance traveled from one frame to the
next divided by the time interval. Average velocity, also referred to as curvilinear
velocity, is then computed as the sum of the frame-to-frame distances traveled,
divided by the total time elapsed. If the temporal sampling rate is constant, this
is the same as averaging the instantaneous velocities. The so-called straight-line
velocity, another type of average velocity, is computed as the distance between
the first and last trajectory positions divided by the total elapsed time. The ratio ...