IDAT106 – Further Bluetooth device location

A bluetooth device is non directional and has no sense of space or direction, it only knows when another device is in range and has started talking to it; so on its own a single device is very limited. A couple of my posts including this address several of the ways useful for visualising the actual space using this data.

Another solution using multiple adapters to extrapolate multiple dimensions is to have multiple devices at a single location. As mentioned in a previous post there are three classes of bluetooth device each with a different theoretical range. The class of adapter can indicate the distance of the detected device. However there will be large variations, for a device to be detected two-way communication must be briefly established, if one device is a Class 3 with only a couple of metres range it will not be able to communicate with a Class 1 device that is 50 meters away because the maximum range between two devices is that of the lowest. However higher class devices also tend to be more sensitive and are able to detect weaker classes’ signals out of those devices normal range so I would expect to see a slightly improved range for them. This will mean that detecting class 3 devices may not be possible with a class 1 device on the other side of the road.

With three bluetooth adapters each indicating various distances it can be possible to locate a device within this space. If the device appears on all three adapters the device must be passing closely to the scanner. If it appears on the class 1 adapter only then it can be determined to be beyond the range or penetration of the other scanners. One problem is that cars provide shielding preventing bluetooth contact, possibly only allowing the most powerful adapter to detect it. When this is combined with the use of multiple locations to determine speed and therefore the method of locomotion these can be correctly identified as cars due to the unique ID and displayed correctly. Further testing is required to identify if this is viable.

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