[dorkbotpdx-blabber] Fwd: [freegeek-social] Bike Counter for WNBR -- ideas? volunteers?

dan p gunterhausfrau at gmail.com
Thu May 29 01:28:16 EDT 2008


count the number of stickers that were handed out, then you don't have to
worry about where on the nekid body (helmet or non-helmet'd nekidness)? or
if your going to be there handing out stickers, just count the people?

I think the point was a passive system. Does the counter need to be at the
starting line when the concentration would be the highest? have one there,
then one 1/4 mile away?




On 5/28/08, Mykle Hansen <mykle at mykle.com> wrote:
>
> not to be a sticker in the mud, but a whole lot of people
> consider "naked" and "wearing a helmet" to be separate states.
> i'm not here to fan the flames of the bike-helmet wars --
> i have a whole other mailing list if i want that kind of pain --
> but i don't think that stickers are going to get the penetration
> you need for an accurate count.  any other bike ride, maybe, but
> this one i dunno.
>
> you could still make a statistical count, if you could generate
> some kind of assumed percentage of riders who have stickers --
> take a random sample somehow -- and then expand that to the
> whole count.  but it seems like a lot of work for a hard-to-define
> level of accuracy.
>
> -m-
>
> On May 28, 2008, at 7:40 PM, subbies at redheadedstepchild.org wrote:
>
>  wellllll, you could even throw in the last
>> colored-sticker-on-helmet-for-Processing in tandem with my idea
>> (making it colored sticker on helmet with number) and thereby try *three*
>> out all at once.
>> -Alexis
>>
>> + --------
>>   redheadedstepchild.org
>>        ------- +
>>
>> On Wed, 28 May 2008, Donald Delmar Davis wrote:
>>
>> ::How about we pick 2 methods (ground sensor image processing) with
>> alexis's
>> ::sticker idea as a control mechanism and implement them.
>> ::
>> ::Document the results.
>> ::
>> ::
>> ::Management. We need some management here.....
>> ::
>> :::)
>> ::
>> ::On May 28, 2008, at 10:23 AM, Mykle Hansen wrote:
>> ::
>> ::>
>> ::> On May 28, 2008, at 7:42 AM, Jason Plumb wrote:
>> ::>
>> ::> > I've always wondered how those things work and what the response
>> rate is
>> ::> > like.  Do they really just give an on/off or are they using a
>> summing
>> ::> > pressure system of some kind?  Are they *really* capable of
>> detecting when
>> ::> > two cars/bikes pass over very *very* close together?  Just given the
>> ::> > number of cars on the road, isn't there a pretty high statistical
>> ::> > probability that two will hit in the same millisecond (or
>> lower)...so how
>> ::> > do *they* handle it?
>> ::>
>> ::> i don't know exactly how, but here is a paper from 2002, in which
>> ::> NZ traffic engineers tested some of the tube devices on the market
>> ::> for counting both cars and bikes:
>> ::>
>> ::>   http://www.ipenz.org.nz/ipenztg/papers/2002_pdf/34_MacBeth.pdf
>> ::>
>> ::> i worry, tho, that with their sample size of 50 bikes they're
>> ::> not close to hitting the level of traffic we're expecting.  on the
>> ::> other hand, it's all about the sample rate ... not just the chip,
>> ::> tho, it's also limited by the properties of air in a tube.  but
>> ::> if the rate is high enough, it ought to be able to reduce this
>> ::> problem to an acceptably low level.
>> ::>
>> ::> > At 15mph, bikes wheels spaced 1.3cm apart will hit the sensor within
>> 2ms
>> ::> > of each other (hitting Paul's 500MHz example).  1.3cm ain't big, but
>> it
>> ::> > also ain't tiny.  I could see this happening in reality....so the
>> question
>> ::> > is, what do you do with the missing/bad counts/anomalies?  Is it ok
>> to
>> ::> > drop somebody?
>> ::>
>> ::> one option is to funnel the ride through some narrow counting
>> ::> point where the possibility of side-by-side riders is lower,
>> ::> and lay the tube there.  another is to use multiple counters
>> ::> in multiple locations and average the results.  (i was going
>> ::> to suggest running a group of tubes at different angles, until
>> ::> i imagined riding over that naked. =)
>> ::>
>> ::> -m-
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