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

[Frank Canaan]

Chances are a cattle chute setup will make almost all of these ideas easier
to implement... Funneling people into a thinner stream will make things more
accurate.

On Wed, 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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-- 
-Frank Canaan
fcanaan at gmail.com
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