State of the Art - Smartphone-Based Human Activity Recognition - page 37

Table 3.1 Classification of activities by duration and complexity
Duration/complexity

Activity type Examples

Short events Gestures Waving hands, nodding head, laughing

Transitions Stand-to-sit, lie-to-sit

Basic activities (BAs) Static Standing, sitting, reading

Dynamic Walking, running, cycling

Complex activities (CAs) Multi-activity Cooking, assembling furniture, weight training

Multi-user Talking, ballroom dancing, hugging

The second group is composed of Basic Activities . They are mostly characterized
either by a continuous or a cyclic action. Their duration is variable but in general
they take much longer than short events (in the order of minutes). Two activity types
are derived from this class: Static which involve Static Postures (SPs) such as sitting
and standing and dynamic which are activities that have periodicity such as walking
and running (here we will refer to them as Ambulation Activities (AAs)). Finally,
the third group is the one of Complex Activities ( CAs ). This comprises the rest of
activities which are generally a sequence of BAs and short events ( multi-activity )
or that involve more than one subject ( multi-user ) such as ballroom dancing which
requires the participation and coordination of two people while performing several
movements.
There are currently many applications of public interest where HAR is greatly
needed. For instance: in healthcare, for tailoring medication of disabled patients with
motor problems through the continuous monitoring of locomotion and daily living
activities using inertial sensors, and in security, for the surveillance of public places
and crime prevention through the detection of security -related activities using video
cameras (Avci et al. 2010 ; Lin et al. 2008 ). In this manner it is possible to see a clear
categorization of activities according to their type. These groups of activities are, in
general, relevant to various HAR applications. Table 3.2 depicts different types of
activities which have been employed in previous studies. Other proposed taxonomies
of activity type are presented in Bruno et al. ( 2012 ); Lara and Labrador ( 2012a ).

Table 3.2 Classification of activities by type
Application

Examples

Daily living Watching TV, ironing, eating, showering, cleaning

Locomotion Walking, riding, standing, laying down, falling

Sports/fitness Jumping, weight lifting, climbing, swimming

Communication/connectivity Phone calling, texting, talking, signing

Security/surveillance Loitering, chasing, supervising, stalking