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help with multilateration wikipedia webpage explanation

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Last Modified: 2012-08-14
Trying to understand the wiki explanation of multilateration below;
Is Tc i.e. the central site... Is this the emitting tag or another reader?
I am trying to design a simple RFID locating system using DTOA.
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Tc is one of four readers, the emitting tag is at (x,y,z).
Of course with (usually passive) RFIDs, the RFID tag is only a "secondary" emitter, induced by some primary emitter - which *may* be identical with one of the four receivers

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I am using cheap active tags for the purpose of the project. Do I need 4 readers or can I do with three since after all the simualtion is a bird's eye view so this would be 2D? Or am I misunderstanding the concept?
If the location of the target object is constrained to a plane, and you have 3 sensors in the same plane, you ought to be able to locate the object.


Also what is the minimum distance that can be allowed between the reader and the tag and the readers between each other. I know that the tag cannot be detected by the reader correctly unless it is more than a metre from the reader as per the specifications posted with the devices. I have heard that the DTOA is usually used on a large scale while RSS is used on the smaller scale. Is this true. I cannot use RSS as the tags do not allow for this functionality. What is the reason for the minimum distance that you advise above.


If you ask generic questions about geometry, triangulation or multilateration, then I might be able to help you.  If you ask specific questions about specific unnamed RFID components then I really can't help you.
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