Obtaining Distance from RSSI

There’s an interesting article on Medium on “How iBeacon technology is used to identify empty space with simple formula”. However, the article is more about how to use beacon received signal strength (RSSI) to calculate distance:

“Build a mobile app that can receive signals from iBeacon and calculate the distance between an iBeacon and itself with an error margin of 10 to 15 meters.”

This implies that the error is usually more than 10 to 15 meters and with extra processing only 10 to 15 meters accuracy can be achieved – this is misleading. The error depends on many factors including the type of beacon used, the capability of the receiving device, the distance of the beacon from the ground (and obstacles) and importantly the distance of the beacon from the receiving device.

The closer the beacon is to the receiver, the more accurate the derived distance. As our article mentions, projects that get more detailed location derived from RSSI, usually via trilateration and weighted averages, usually achieve accuracies of about 5m within the full range of the beacon or 1.5m within a shorter range confined space.

The medium article contains links to some useful Android Java code if you want to experiment with extracting distance from RSSI.

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