On the assumption that the droplet is at rest on a solid surface and reaches equilibrium quickly, if compared to differences at a certain time after the droplet is deposited, the contact angle data of the preceding paragraph is very useful. However, this only applies if the data is not altered much. For example, assuming a case of various states, such as coating or cleaning where the liquid and solid interface is dynamic, sufficient data is not obtained.
This case simulates (with the advancing contact angle and receding contact angle) a dynamic situation, where the liquid droplet interface moves and has been increasing. Conducting this analysis with a personal computer has become common practice, so you can easily capture dozens of frames per second to measure the time-dependent change of the droplet (contact angle).