Returns a conservative estimate of the current maximum horizontal distance to the beacon. This value will increase over time as the estimated distance becomes increasingly uncertain until a new measurement is received.
Update the estimate for the true RSSI using a 1D Kalman filter. Prediction stage: x̂ₜ₍ₜ₋₁₎ = Fₜ * x̂₍ₜ₋₁₎₍ₜ₋₁₎ + Bₜ * uₜ Pₜ₍ₜ₋₁₎ = Fₜ * P₍ₜ₋₁₎₍ₜ₋₁₎ * Fₜᵀ + Qₜ