Precision
The repeatability or consistency of position measurements - how close repeated measurements are to each other. Different from accuracy (closeness to true position). High precision with low accuracy means measurements are consistent but systematically off. High precision and accuracy means consistent measurements close to truth. Both important for RTLS performance.
Statistical measure of measurement consistency or repeatability, quantifying random errors in positioning.
Precision quantified by: standard deviation of repeated measurements at fixed position (typical: 5-15 cm for UWB, 0.5-2 meters for BLE), circular error probable (CEP: radius containing 50% of measurements), 2DRMS (twice distance root mean square, radius containing approximately 95% of measurements). Factors affecting precision: (1) Measurement noise - random fluctuations in signal detection (thermal noise, environmental RF, electronic noise). (2) Multipath variations - reflections changing dynamically as environment changes. (3) Processing quantization - discrete measurement steps (eg., timing resolution of 1 nanosecond gives 30 cm ranging quantization). (4) Atmospheric conditions - temperature, humidity affecting signal propagation. (5) Anchor clock drift - small variations in anchor timing between synchronization updates. Improving precision: (1) Signal processing - filtering measurement noise through averaging and sophisticated detection algorithms. (2) Kalman filtering - smoothing position estimates reducing random variations. (3) Higher-quality hardware - better receivers with lower noise figures, more stable oscillators. (4) Increased measurement samples - averaging multiple measurements per position update. (5) Environmental control - reducing dynamic changes causing measurement variations. Industrial RTLS precision expectations: UWB systems typically achieve 10-20 cm precision (repeated measurements scattered within 10-20 cm radius), BLE/Wi-Fi 1-3 meter precision, active RFID zone-level precision. Precision testing: placing stationary tags, collecting measurements over minutes/hours, calculating standard deviation of positions. Precision typically better than accuracy: systems often achieve 10 cm precision while accuracy is 20-30 cm (indicating precise measurements consistently offset from true position, improvable through calibration).