Tools to determine exact location when using ibeacons

Question

We are working with a Retail client who would like to know if using multiple iBeacons throughout the store would help track a customer\'s exact location when they are inside the

Answer 1

Obviously this is unlikely to work well due to the inconsistency of the RSSI value (bluetooth signal). However, this is the direction you may want to take it (adapted from lots of stackoverflow research):

Filter RSSI

I use a rolling filter with this whenever the beacons are ranged, using a kFilteringFactor of 0.1:

rollingRssi = (beacon.rssi * kFilteringFactor) + (rollingRssi * (1.0 - kFilteringFactor));

And I use this to get a rolling Accuracy value (in meters). (Thanks David!)

- (double)calculateAccuracyWithRSSI:(double)rssi {
    //formula adapted from David Young's Radius Networks Android iBeacon Code
    if (rssi == 0) {
        return -1.0; // if we cannot determine accuracy, return -1.
    }


    double txPower = -70;
    double ratio = rssi*1.0/txPower;
    if (ratio < 1.0) {
        return pow(ratio,10);
    }
    else {
        double accuracy =  (0.89976) * pow(ratio,7.7095) + 0.111;
        return accuracy;
    }
}

Calculate XY with Trilateration (Beacons 1, 2, and 3 are Beacon subclasses with pre-set X and Y values for location and distance is calculated as above).

float xa = beacon1.locationX;
float ya = beacon1.locationY;
float xb = beacon2.locationX;
float yb = beacon2.locationY;
float xc = beacon3.locationX;
float yc = beacon3.locationY;
float ra = beacon1.filteredDistance;
float rb = beacon2.filteredDistance;
float rc = beacon3.filteredDistance;

float S = (pow(xc, 2.) - pow(xb, 2.) + pow(yc, 2.) - pow(yb, 2.) + pow(rb, 2.) - pow(rc, 2.)) / 2.0;
float T = (pow(xa, 2.) - pow(xb, 2.) + pow(ya, 2.) - pow(yb, 2.) + pow(rb, 2.) - pow(ra, 2.)) / 2.0;
float y = ((T * (xb - xc)) - (S * (xb - xa))) / (((ya - yb) * (xb - xc)) - ((yc - yb) * (xb - xa)));
float x = ((y * (ya - yb)) - T) / (xb - xa);

CGPoint point = CGPointMake(x, y);
return point;