Occupied regions are determined using a presence sensor. In
particular, we propose an ultrasound based array sensor to determine
presence and location of occupants. Ultrasound sensors
provide an active way to monitor presence in large volumetric
spaces and are potentially more sensitive than passive infrared sensors.
Ultrasound sensors have been used for occupant detection in
the past [7,13,18,23]. Past solutions were single element sensors
based on either time-of-flight or Doppler measurements, and only
provided binary room-level occupancy information.