# Determin position with Algorithm 3 circle?

I can’t determin position with Algorithm 3 circle ! Because distance from 3 beacon to user not exactly. But use IndoorLocationSDK then dependence in floor. Please help me

Hi hungnt,
do I understand correctly you are using exact intersection of three circles to find the position of the user?

The case here is that measurements provided by beacons contain noise, and due to that it is hardly ever possible to get three “exactly” matching measurements. Thus, one has to be a bit smarter and use some slightly more sophisticated methods to handle the uncertainty.

The simplest I can think about is trilateration (check for example https://en.wikipedia.org/wiki/Trilateration )
It might require solving a system of equations (derived from geometry), where your unknown is the (x,y) position of the phone, and (r1, r2, r3) are the distances from beacons. Having the equations, one can use for example least squares to get the approximate solution. I believe you can find plenty of examples how to do that on the Internet.

I hope that helps! Let me know if you have further questions.
Cheers!

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Thanks marek_syldatk!

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