What does a twin that assumes the radar is aligned with the body get wrong about dead reckoning, and can loop-closure validation see it?

research/mount-twin

A radar twin assuming the sensor is body-aligned: planar dead reckoning is exactly the true path rotated by the mount yaw (error 2 sin(e/2)·|displacement|, bounded, zero after loops, so loop-closure validation is blind), closed-form rotation fit with std σ/√Σ|p|², but a pitched mount drifts vertically laps·2πR sin e.

6 tests

What it found

With a planar mount-yaw error e, radar ego-velocity dead reckoning is exactly the true path rotated by e: error 2 sin(e/2)·|displacement|, bounded by the path diameter and zero after any closed loop, so loop and out-and-back validations pass while a straight 157 m run is off by 27 m at 10°. A closed-form rotation fit recovers e with standard deviation σ/√Σ|p_i|² (matched by simulation, 95% coverage). Stylised: the result is planar; a pitched mount drifts vertically by exactly laps·2πR sin e despite perfect x-y closure.

A figure from its own output

Figure produced by research/mount-twin: err_vs_yaw — mount-twin/experiments/err_vs_yaw.svg, written by the project's own experiment code.

Paper, code and results

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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.