I believe the term “Presence” takes on multiple levels of granularity, which could be serviced by different techniques;
- Intra-building: Within a room in a building (e.g, FIND, bluetooth beacon, or similar). If facial recognition is to be considered, it invariably should be enhanced by tracking via Kalman filters (or similar) which would benefit very significantly from tracking the head (front or side) and upper torso of any individuals that have been facially recognized (as actual facial recognition events may be few and far between). This requires cameras in many (if not most) locations in and around the building, and is a fairly complex solution. I had made progress in this direction until a lightning strike knocked out my system and I rediscovered life outside of OH.
- On Premises: Inside or within a very short distance of a building or other finite location (e.g, geofence of 7 to 50 meters from building/location boundary, depending on location ‘footprint’ and urban/suburban/exurban density considerations). Phone WIFI presence could work here.
- Near Premises: Within some end user definable distance as ‘near’, in order to identify when a person is approaching/leaving home for purposes of HVAC control, outside light control, setting security system mode, etc. There could be multiple geofences of differing distances for different purposes (as HVAC control may need more time to ramp up, as one example) 0.5 to 3 kms might be such example distances, with the aforementioned urban/suburban/exurban considerations. Owntracks or other solutions could work here
- Away: Anything considered beyond ‘Near Premises’. Owntracks or similar could work well here. There could also be multiple such levels, if purposes warrant.
So Presence could be an object with the attributes 'location" and “time”, with the location attribute defined by rules that focused on the most granular location systems first per their availability.
Timeliness is another important aspect, as different User Stories have differing needs. Knowing the presence of a person with respect to whole house HVAC or security mode settings only requires knowing within a 10-20 seconds that a person has entered or exited a zone. Lighting or ‘following’ music, as two examples, would be expected to react within 1-2 seconds. Zone/room HVAC would be expected to react within 5-10 seconds, though behavior interpretation via video analytics (such as recognizing that a person just sat down) would be highly preferable to preclude starting up a system to respond to a person who walks into a room, picks up something, then leaves (which has obvious HVAC efficiency penalties). One could take this to extremes, of course, so it goes without saying that understanding the actual need should drive any system analysis of alternatives and corresponding architecture.
Hence, “Best Presence Detection” may likely be a combination of techniques tailored to the specific circumstances and objectives.
(have created a new thread for purposes of the larger context of Presence discussion)