A support device for supporting the body of a person, the support device comprising: an inflatable layer (20) formed of a plurality of inflatable cells communicating with inflation and deflation means； a sensor pad (102) arranged below the inflatable layer (20), the sensor pad (102) comprising at least one sensing element (104) configured to sense the load applied to the or each sensing element (104)； and electric circuitry (108) connected to the or each sensing element (104) of the sensor pad (102), the electric circuitry (108) being configured to: control the inflation and deflation means for filling or emptying, respectively, the inflatable cells (22) of the inflatable layer (20) in such a way that the internal air pressure of the inflatable cells (22) is a function of the load of the body of a person resting on the support device as sensed by the or each sensing element (104), and determine the position on the support device of a person resting on the support device based on the load sensed by the or each sensing element (104).
