How to Calculate the accurate distance from nearby bluetooth device like mobile phones in iOS?

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Created Aug ’20

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I search the nearby Bluetooth devices. And using the RSSI and tx-power value (tx-power hardcoded power value Usually ranges between -59 to -65) the distance by this code.

func calculateNewDistance(txCalibratedPower: Int, rssi: Int) -> Double{
    //txCalibratedPower : hard coded power value. Usually ranges between -59 to -65
    if rssi == 0 { return -1 }

    let ratio = Double(exactly:rssi)!/Double(txCalibratedPower)
    if ratio < 1.0{
      return pow(10.0, ratio)
    }else{
      let accuracy = 0.89976 * pow(ratio, 7.7095) + 0.111
      return accuracy
    }
  }

But didn't get that much accuracy.

For android, they use the Kalman filter to remove the noise between the path and calculate the distance (80 - 85 %) accuracy.

So anyone helps me out to calculate the distance.

Question is already here but didn't have a solution : [https://stackoverflow.com/questions/3624945/how-to-measure-distance-between-two-iphone-devices-using-bluetooth)

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Answer 1

Claude31 OP

Aug ’20

Please refrain from asking the same question several times. Better look at answers and tell what you did or could not do with it.
https://developer.apple.com/forums/thread/656117

This being said, BT will not give you an "accurate" distance. Received signal strength depends on propagation conditions. And you should precise what accurate here means for you.

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