Oli Glaser wrote:
>> 2 - You still rely on knowing parameters of the train, which in this
>> case is the spacing between wheels.
>
> Of course, but I thought that part was rther obvious.. :-)

But yet you suggested a method with this obvious drawback.

> Note the "something like" in my post - it depends a lot on what
> information is available, and the situation (which I am mostly in the
> dark about)
> For instance, if all trains are a standard length, then it could be as
> simple as timing the duration of the noise.

Why go to great lengths to concoct a system that might sortof work if
everything is right and only Standard Trains pass by, when much simpler and
reliable methods are readily available?

> plenty of ways to do this..

That's the point.  There are plenty of ways that can be dreamt up to do
this, but not that many that are simple to implement, reliable, cheap,
readily doable, and don't require the train to be just right.  As I
understood the question, it was a practicle one, not a theoretical one.  Do
you really think futzing around with a DSP algorithm to detect the right
sound, and then assuming a particular wheel spacing makes sense as a method
of getting the job done?  Do you really think that is quicker to implement
and tweak than a couple of magnetic sensors, and that it will work in more
circumstances and stay working in the real world longer?  Right, I didn't
think so.

While it may be interesting from a theoretical point of view, it's frankly
silly if you just want to solve the problem.  If you want to muse about
theoretical solutions, thats fine as long as you label them as such.  Your
message made it sound like you were seriously proposing this as a real
solution, which is doing the OP a disservice.


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