Building an Indoor Positioning App with Wi‑Fi RTT
summary
Explains how to measure distance to Wi‑Fi access points on Android using RTT (802.11mc/FTM) available from Android 9 (API 28) and compatible hardware (tested on Pixel 3 + Google Wi‑Fi). Describes using RTT timestamps (t1–t4) to compute round‑trip time and distance, the practical problems of negative/noisy readings, and that trilateration needs ≥3 APs (4+ for ~1 m accuracy). Covers measurement rates (~500 ms), platform throttling (background once/30 min, foreground 4/2 min), and advises outlier filtering, height and sensor fusion, and careful AP placement for real deployments.
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chapters (12)
- 0:00Start
- 6:26More details on distance measurement
- 8:05When there is only one access point
- 9:05Method introduced at Google I/O
- 9:53Expressing with Pythagorean theorem using equations
- 10:43Drawing linear equations
- 13:10Scanning Wi-Fi access points
- 14:16Obtaining distance to access points
- 22:52Installing access points
- 23:45Creating the app
- 24:34Improving accuracy 1
- 26:51Demo here
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