What does a simulator tuned on one-step odometry noise get wrong about drift, relocalisation and loop closure?

research/odometry-twin

A twin tuned on one-step odometry noise cannot see drift: variance ratio exactly 1+(T−1)ρ, relocalisation interval 3.4× too long (real miss 51.6% vs 5%), twin-tuned loop-closure gate recall 0.64 at T=200, closed-loop runaway, aliasing limits calibrated gates.

10 tests

What it found

A traversal has a persistent bias plus white noise, so real error after T steps has variance σ₁²(ρT²+(1−ρ)T); a twin fitted to one-step increments, identical for every ρ, predicts σ₁²T and is off by exactly 1+(T−1)ρ. With 5% of step variance persistent, the twin’s relocalisation interval is 3.4× too long (real miss probability 51.6% against a claimed 5%), and a 3σ loop-closure gate tuned in it accepts true closures with probability 0.64 at T = 200 instead of 0.997; in a closed loop the rejections let error run away (RMS 8.8 m against 0.17 m calibrated). A calibrated gate accepts 97–99% of aliased closures once drift uncertainty exceeds the alias offset, and a variance ratio fitted at one loop length does not transfer to others. Stylised: 1-D Gaussian, assumed one-step-fitted twin, no real odometry data.

A figure from its own output

Figure produced by research/odometry-twin: closure_recall — odometry-twin/experiments/closure_recall.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.