motion detection
process of detecting a change in the position of an object relative to its surroundings or a change in the surroundings relative to an object
en-US/ˈmoʊʃən dɪˈtɛkʃən/
en-GB/ˈməʊʃn dɪˈtɛkʃn/
process of detecting a change in the position of an object relative to its surroundings or a change in the surroundings relative to an object