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[aprssig] APRS RFID reader?

Patrick winston at winston1.net
Tue Feb 2 14:27:28 UTC 2010

I'm  not so sure that it really matters when people are leaving places  
though..  I'd think the idea for this sort of system would be that at  
1323 today I was at the EOC, weather coming or going..  I'd see this  
expiring with a high decay rate, so you could have multiple readers  
through a facility which would feed the network that you're still  
there, but after 20 minutes of no beacon I don't think it would be a  
safe bet to assume people are still there..

That said, I don't believe it should be too hard to come up with a  
design for a 2 stage reader which is able to infer directionality  
based on which order the two readers read the tag, as long as both  
readers do read it of course.


Quoting "Lynn W. Deffenbaugh (Mr)" <ldeffenb at homeside.to>:

> Richard Amirault wrote:
>> Easy ... if you are not there .. and you trigger the sensor .. then  
>> you *are* there.
>> If after you are there .. you once again trigger the sensor .. then  
>> you are *not* there.
> Not so easy.  Miss one update and the state is then reversed.   
> S/He's there when gone and gone when there.   And then you say, but  
> put a timeout on it.  A person will never be there longer than 12  
> hours....Oh wait, there's 24 hour contests, ok, so force them to be  
> gone after 24 hours....Oh wait, they might move in to the station to  
> staff a hurricane for 2-3 days, so we'll time it out in that  
> time....Oh wait, this person is a hard-core station user that comes  
> and goes every other day, so s/he'll be perpetually in the wrong  
> state.
> I do RFID systems professionally.  If your reader's can't give you  
> direction of motion, there's no 100% reliable way to infer such  
> information.  Any such inference amounts to an assumption of some  
> kind and we all know what happens when we AssUMe.
> Lynn (D) - KJ4ERJ - Recloaking for this discussion
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