Human motion monitoring has become a highly active topic in various research areas because of its potential for understanding people’s activities, intents, and even health statuses. The ability to continuously and consistently monitor human motion is an important function in numerous applications, including surveillance, control, and analysis [1]. A typical surveillance application is abnormality detection in public areas. Human–computer interface is a well-known example of control applications. In terms of analysis applications, patient diagnostics and athletic performance analysis are receiving more and more attention from both researchers and practitioners [2–4].