Activity Detection Method A motion sensor, device and corresponding computer program

This method of detection of the activity (A) of a carrier physical system of a motion sensor includes the following steps: extracting (100) a sequence (M) from measurements supplied by the motion sensor; deduce (102) a sequence of observation (O) calculated from the sequence of measurements (M); using a statistical model component of the observation sequence in the light of a predetermined plurality of possible states in which can be found on the physical system, determining (104) the activity (A) of the system physical in the form of a sequence of states corresponding to the observation sequence. At least one component of the observation sequence (O) is calculated from a reference value (lambda) of a representative vector of a reference axis. In addition, the method comprises the following calibration steps: calculating (106) a likelihood value of the observation sequence (O) on the basis of said statistical model; depending on the likelihood value, decision on the estimate (108) of a new reference value (lambda) of the vector representing the reference axis.