RTLS accuracy — what the numbers actually mean.
Every RTLS vendor quotes an accuracy number. They mean different things. "30 cm UWB" at 95th percentile in a clean lab is not the same as "30 cm UWB" at 50th percentile in a production environment.
Per-technology realistic accuracy under production load.
UWB (TDoA, well-designed): 10–30 cm @ 95th percentile controlled; 30–60 cm in a typical industrial bay; degrades to 100+ cm if anchor density is wrong.
BLE-AoA: 50 cm to 2 m @ 95th percentile depending on Locator density, antenna geometry and ceiling height.
RAIN RFID (location-grade): 1–3 m at item-level under a ceiling phased-array; presence at portal read points.
GPS / GNSS (standard): 3–5 m outdoor; does not work indoors.
GNSS-RTK: 1–3 cm outdoor with corrections; requires unobstructed sky view.
LoRaWAN geolocation: 100–500 m via TDoA across multiple gateways; good for presence, not position-precise.
SLAM (visual / lidar): 5–20 cm in mapped environments; degrades sharply if the environment changes.
Why vendor accuracy claims are usually 95th percentile under lab conditions.
Most spec-sheet numbers assume line-of-sight, designed-density placement, calibrated mounting, no production-load interference, single-tag testing.
Real production environments degrade those numbers by 30–100%.
Ask vendors to quote 95th-percentile accuracy under your environment. They will resist; that resistance is the answer.
How accuracy degrades — the five common causes.
Multipath from metal racking, glass, stainless panels, concrete-aggregate floors, HVAC ducting.
Anchor mounting height drift — 200 mm off design changes UWB cone of coverage by 15–25%.
Synchronisation drift — TDoA requires nanosecond sync; mis-cabled PoE switch quietly destroys accuracy.
RF blockers introduced post-survey — racking, guarding, mezzanines.
Production-load interference — forklift mast occlusion, dock-door cycles, press cycles.
Frequently asked questions
What accuracy does my use case actually need?
Asset tracking in a warehouse: 1–3 m. WIP on a production line: 30 cm. Hospital workflow: room-level (1–3 m), sub-metre for bed/equipment. Public-safety training: 10–30 cm.
Why does my pilot accuracy drop on day 60?
Almost always because the bay was empty during commissioning and full of racking and traffic by day 60. The RF environment changed.
Can RTLS accuracy be guaranteed contractually?
Vendor SLAs guarantee accuracy under their installer’s commissioning conditions, not under your production load. That is why most programmes hit the SLA on paper and miss the operational KPI.
What is the difference between 50th and 95th percentile accuracy?
50th percentile means half of measurements are within that number; 95th percentile means 95% are. A vendor quoting "30 cm" without specifying percentile usually means 50th percentile, which is significantly looser than 95th.
Last updated: