I found the example I mentioned in case anyone is interested in the future,
turns out it was a UCSD student project that they have now turned into a
company -  https://waitz.io/  Currently, it looks like it is used in McGill
and UCSD libraries and maybe others? They have done some product
development on it, but under the hood each device is just a raspberry pi, I
believe.

They have a fancier algorithm for getting more accuracy, but I am just
doing basic counting/deduping of any bluetooth-enabled devices in range of
the Pi and then dumping the address data and just retaining the count for
privacy purposes. So just using the onboard bluetooth chip with the pybluez
python library, no additional sensors necessary, can scan the environment
and tell you there are X number of devices in range with bluetooth on. Run
and observed repeatedly you can then get a sense of the space's
baseline and changes over time.

To do entrance/exit detection external sensors are needed (wired to a Pi or
Arduino), e.g. using PIR motion sensor or ultrasonic range sensor similar
to the approach in the article Tom posted ->
https://journal.code4lib.org/articles/12947 This is very straightforward if
there is a dedicated entrance and exit. If it's bi-directional foot traffic
you'd need a set of sensors to determine direction, e.g. in a meeting room
to be able to say there have been 10 entrances and 5 exits so let's assume
about 5 people inside. You could also get very fine-grained and use
pressure sensors on each seat to tell if it's occupied or not (places like
We Work do this).

Kun - if you'd like to discuss further feel free to email me directly my
contact info is in my signature, always happy to talk about sensor stuff!

Best,

Monica Maceli, Ph.D.
Associate Professor
Pratt Institute | School of Information
144 W 14th St, 6th Floor, New York, NY, 10011-7301
www.monicamaceli.com | [log in to unmask]


On Thu, Jul 9, 2020 at 12:32 PM Kun Lin <[log in to unmask]> wrote:

> Hi Monica
> Could you let me know what kind of sensor you are using? The bluetooth
> scanner, are you referring to scanning for bluetooth device or it's a
> bluetooth connection to your computer?
>
> Thanks
> Kun
>
> On Thu, Jul 9, 2020 at 7:54 AM Monica Maceli <[log in to unmask]> wrote:
>
> > Hi all,
> >
> > I have been experimenting with entrance/exit sensors (pir and/or
> > ultrasonic) combined with a Bluetooth scanner running on Pis to calculate
> > relative space crowdedness for our campus.  Data is sent over wifi via
> MQTT
> > to a cloud Influxdb database w/ Grafana for data dashboard and alerting.
> I
> > don't have published code currently but I'd be happy to share and work
> with
> > others on this.
> >
> > I too felt that the cameras, while doable and probably more accurate,
> would
> > introduce too many privacy concerns.
> >
> > I got the Bluetooth idea from a project I heard about awhile ago, but I
> > can't remember the original creator (I think a librarian had these placed
> > in a library and a Redditor found a Pi and posted a "what is this thing?"
> > post). Does this ring any bells?
> >
> > Best,
> >
> > Monica Maceli, Ph.D.
> > Associate Professor
> > Pratt Institute | School of Information
> > 144 W 14th St, 6th Floor, New York, NY, 10011-7301
> > www.monicamaceli.com | [log in to unmask]
> >
> >
> > On Wed, Jul 8, 2020 at 8:57 PM Tom Keays <[log in to unmask]> wrote:
> >
> > > There was this write up from 2017 in the C4L Journal. Not cameras, but
> > > other kinds of sensors that didn't trigger any privacy concerns.
> > >
> > > https://journal.code4lib.org/articles/12947
> > >
> > > On Wed, Jul 8, 2020 at 1:20 PM Goben, Abigail H <[log in to unmask]>
> wrote:
> > >
> > > > I think Griffey did
> > http://jasongriffey.net/mtf/homepage/feed/index.html
> > > >
> > > >
> > > > --
> > > > Abigail H. Goben, MLS
> > > > [log in to unmask]
> > > >
> > > > -----Original Message-----
> > > > From: Code for Libraries <[log in to unmask]> On Behalf Of Kun
> > Lin
> > > > Sent: Wednesday, July 8, 2020 12:02 PM
> > > > To: [log in to unmask]
> > > > Subject: [CODE4LIB] Anyone attempted to use Raspberry Pi w/camera to
> > > > monitor building capacity?
> > > >
> > > > Anyone attempted to use Raspberry Pi w/camera to monitor building
> > > > capacity? Any good resources on how to do that?
> > > > Thanks
> > > > Kun
> > > >
> > >
> >
>