[unisog] Wireless in residence building - Tricky problem

Matt Crawford crawdad at fnal.gov
Wed Nov 5 21:27:14 GMT 2003

On Wednesday, Nov 5, 2003, Mitch Collinsworth wrote:

>>> I don't see why triangulation wouldn't be considered 
>>> incontravertable,
>>> though it's safer to do it with 3 samples, since doing it with 2 only
>>> gets you to one of 2 possible locations.


> When using 2 sampling points that produce 2 possible locations, the
> 2nd possible location is not on the other side of the earth.  It's on
> the other side of the line segment that connects the 2 sampling points.

I believe you are imagining some sort of equipment that measures the 
distance to the transmitter, not the direction from the equipment to 
the transmitter.  (And in your case, the measurements establish a 
three-dimensional surface on which the transmitter may lie.)

Two *direction measurements* establish at most one contiguous volume 
which contains the transmitter, and whose size depends on the accuracy 
of the measurements.

If you still disagree, please draw me a picture or show the math.

                 Matt Crawford   <crawdad at fnal.gov>
                 Fermilab Computer Security Coordinator

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