Dead Reckoning

A positioning technique estimating current location by calculating movement from a known starting position using motion sensors (accelerometers, gyroscopes). Maintains position estimates when primary positioning signals are temporarily unavailable. Particularly valuable for personnel tracking in areas with intermittent coverage like stairwells or elevators. Accuracy degrades over time due to sensor drift, requiring periodic corrections.

Position estimation technique using last known position plus velocity and direction to predict current location when direct position measurements unavailable. In industrial RTLS, dead reckoning uses integrated accelerometers and gyroscopes (inertial measurement units) to track movement during coverage gaps. Tag records last reliable position from RTLS infrastructure, then uses IMU to calculate displacement and update estimated position. Dead reckoning accuracy degrades rapidly due to sensor drift - typically 1-3% of traveled distance per update. For example, 10-meter movement accumulates 10-30 cm error, compounding with each step. Industrial applications include: maintaining approximate position when tags temporarily lose RF connectivity (moving behind metal equipment, inside containers), reducing required infrastructure density in low-accuracy zones, and improving position smoothness in challenging RF environments. Advanced implementations use particle filters or Kalman filters combining dead reckoning with periodic RTLS updates, providing optimal position estimates. Dead reckoning adds $5-15 to tag cost for IMU integration and increases power consumption 10-20%, reducing battery life proportionally. Most valuable in facilities with unavoidable coverage gaps where temporary position estimation prevents complete tracking loss.