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Fig . 6 : Field view of a PIR Sensor
This is useful for occupancy detection , because each individual in an environment will emit light in the infrared region at a higher level than other objects in the space . By separating these individuals with higher light emissions from the area being inspected , the output of the camera will be an image with various “ blobs ” representing each individual person . The “ blobs ” can thus be counted and the number of occupants in space can be measured 12 .
Infrared cameras have the added benefit of being able to anonymously detect the presence of individuals without being dependent on the movement of those individuals . However , challenges occur when individuals are very close to each other and appear as one “ blob ” leading to inaccurate counts .
WiFi
The majority of the large commercial / institutional buildings have WiFi networks . Most of the laptops and smartphones within the building are connected to this wireless network via different access points . This technology can detect both occupants ’ presence and count within the premises and hence can be used to form an occupancy tracking system .
Whenever a person enters the premises with a WiFi-enabled device , such as a laptop or a smartphone , the device scans for the WiFi access points ( AP ) present in the vicinity . Each access point whose range coverage the device is in receives the identification of the device and the strength of the signal that the device is receiving from that particular AP . The former is the MAC ( Media Access Control ) address 12 of the device . The latter is called the RSSI ( Received Signal Strength Indicator ) 13 of the device . Using this data received by the various APs in the vicinity of
- 26 - November 2020