possible to measure distance between two devices?
I'm interested in whether it's possible to measure the distance between two sensors, or potentially the displacement of one over time. It seems that most sensor fusion approaches to estimating position have difficulty due to the error inherent to integrating low-ish resolution acceleration signals.
Anyone have any fun ideas?
Unfortunately distance is not possible to do using Bluetooth. It would be very inaccurate using RSSI.
It is possible to integrate linear acceleration (= acceleration minus gravity) to obtain velocity and position. Due to various errors this works for 1-2 seconds, after which the accumulated error blows up. Zero-velocity update (ZUPT) algorithms exploit the fact that foot-mounted IMUs are fixed to the floor, hence have known zero velocity, during part of each stance phase. So there is established literature (mainly on indoor positioning) on that particular use case, using elaborate algorithms to reduce error.
I myself have been thinking about using a strong magnet and magnetometer to estimate the distance between the two, but have never tried that.
You can do this but it will be fairly erroneous.