[sudo-discuss] shotspotter will be discontinued
GtwoG PublicOhOne
g2g-public01 at att.net
Fri Mar 14 18:49:16 PDT 2014
Anything that can pick up a gunshot will also pick up false positives
such as: fireworks going off, automobiles backfiring, loud motorcycles
starting, and sometimes, basketballs bounced hard on the street and
baseballs hit with bats. That's why audio recording & monitoring is
useful during possible gunshot events.
If all the event-datapoints are logged to a public map that anyone can
click to examine the data more closely, the risk of abuse of any audio
or video transmission or recording function is minimal, because any
abuse or non-essential use of audio/video will be found and exposed quickly.
With appropriate safeguards, audio & video will help catch shooters.
Safeguards would include a rolling record/erase that stores a maximum of
e.g. 15 minutes of recording, centered on the event. With this you can
see e.g. the car drive up before the passenger shoots the pedestrian, or
the souped-up motorcycle start up with loud pops and a roar. The same
actions that trigger saving a recording for evidence, would also put
information to that effect on the datapoint on the map.
The contract terms with the city (which should also be public) should
specify usage for evidence of violent crimes only, and that any abuse of
the recording capability (such as to pull over that motorcycle driver
for a loud exhaust system) would trigger a large financial penalty. If
the city gov is serious about stopping crime rather than e.g. catching
loud motorcycles and illegal fireworks, the city should have no trouble
signing a contract with those terms & conditions.
-G.
=====
On 14-03-14-Fri 5:46 PM, Steve Berl wrote:
> It is a DSP problem that should already be solved. I suspect google
> can turn up a lot of info. I suspect It can likely be implemented on a
> little Linux board computer like a RaspberryPI or similar. Add the
> cost of a microphone, GPS, and mesh networking HW.
>
> Steve
>
> On Friday, March 14, 2014, Jake <jake at spaz.org <mailto:jake at spaz.org>>
> wrote:
>
> I'm glad somebody knows about this! however i would suggest that
> it's not quite as simple to decide "when the big impulse of sound
> starts" without waiting for it to end and then choosing a peak event.
>
> the best i know how to do is a peak detector where you wait for
> the slope of the amplitude to head downward after a threshold is
> achieved, but i think we can do better, and i think we would need
> to if we were going to achieve good results. and the more
> versatile the analysis is better, to reduce false alarms (!) and
> increase detection of events at lower amplitudes.
>
> On Fri, 14 Mar 2014, Steve Berl wrote:
>
> You don't need to record and transmit the audio at all. You
> just need the time of when the big impulse of sound starts,
> which you can do locally. Just transmit the
> time stamp.
> NTP has a lot of the logic built in to discipline a computer
> clock to a few microseconds of UTC time. It works best
> attached directly to a serial port.
>
> Steve
>
> On Friday, March 14, 2014, Jake <jake at spaz.org> wrote:
> I think it would be a positive move. When you hear a
> gunshot outside you want to believe it's far away, somebody
> else's problem.
>
> when you can look at a website and see where the
> gunshots have been over time, you can figure out if it is your
> neighborhood, and decide to talk with your
> neighbors about it. Maybe everybody knows who it is and
> nobody knows what to do about it. You can have subtle,
> problem-solving conversations with people
> that the police obviously are not capable of.
>
> as for the timing data, i think GPS clock is necessary
> to remain synchronized with all the other nodes (plus it
> serves as a handy location resolver) but
> i'm not sure yet what is the right way to stamp the
> audio data. My best guess would be to put the timestamp into
> the audio stream as a second audio
> channel, so that the central processing computer can
> sort it all out and pinpoint the source.
>
> I do think this would be a good opportunity to grow the
> mesh network but i don't know if the mesh group would be
> excited to do it this way.
>
> -jake
>
> On Sat, 15 Mar 2014, Hol Gaskill wrote:
>
> setting up a system like this would have a
> powerful effect on the public safety narrative - if the public
> is able to self-organize a better
> solution at a low cost and
> share the data directly with everyone, it makes
> alot less sense for public officials to propose alternatives
> wherein our freedoms are demanded
> in exchange for
> whatever degree of security is theoretically
> offered. who's saying it has to be the police that respond?
> if the data is made public people
> could show up and
> videotape or whatever, or reconsider going to that
> area within the next hour, generally use that info however
> they see fit.
>
> i think using gps clock signal or a realtime clock
> IC such as a ds1307 we could get pretty good time data. a
> condenser mic doing amplitude
> and spectral (audio range)
> analysis would be enough to check for gunshots,
> maybe car crashes, sirens, etc, without storing or
> transmitting the actual audio. could this
> be a potential optional
> addon module to the mesh nodes?
>
>
> on Mar 14, 2014, Patrik D'haeseleer
> <patrikd at gmail.com> wrote:
> Very interesting! That $264,000/yr fee does
> seem outrageous - once the system is installed, there should
> be relatively little
> maintenance to keep it
> running.
>
> I wonder if the company will be disabling or
> retrieving the microphones when the contract ends. It's
> possible the city is only "leasing" the
> equipment. Or that
> the company has build in some sort of
> self-destruct to prevent cities taking over the network
> without them...
> FWIW, I do think ShotSpotter is a useful
> technology, but it needs to be designed with some ethical
> issues in mind (e.g. not collecting and
> transmitting more
> information than is required for its stated
> purpose). I think that Sudo Room taking over and overhauling
> the existing network in a completely
> open-source
> fashion would be a great thing to do. That way
> people could satisfy themselves that the technology only does
> what it claims to do.
> Patrik
>
>
> On Fri, Mar 14, 2014 at 3:23 PM, Jake
> <jake at spaz.org> wrote:
> what do people think of the shotspotter
> system installed in oakland?
>
> it's a network of microphones on telephone
> poles, each with a GPS (for a precise clock) and a network
> connection. When a gunshot-like
> sound is
> detected, they send the sound and its
> precise timing to a central server that determines the
> location of the shot, and tells the police
> to go there.
>
> some people have expressed concern that the
> microphones are used to spy on people, but it would be
> impossible to hear a conversation
> from the top of
> a telephone pole that wasnt already loud
> enough to be heard inside nearby houses (or the phone in your
> pocket).
>
>
>
> --
> -steve
>
>
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