Asterisk and Obelisk: Motion Codes for Passive Tagging
summary
A passive visual pattern encodes data that a nine‑axis IMU ring reads as a user traces lines; two schemes, Asterisk and Obelisk, convert averaged stroke direction vectors into relative angles. Asterisk with a 45° base angle supports 8^8 = 16.8 million sequences and achieves 95% raw accuracy; with Hamming error correction it drops to ~10,000 sequences at ~98% accuracy with ~10 s scans. Three‑centimeter strokes outperform 1.5 cm, decoding is orientation‑independent, and in‑air scanning also reaches >95% with error correction.
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