Using Kalman Filter The Right Way: Noise Estimation Is Not Optimal

Determining the noise parameters of a Kalman Filter (KF) has been researched for decades. The research focuses on estimation of the noise under various conditions, since noise estimation is considered equivalent to errors minimization. However, we show that even a seemingly small violation of KF assumptions can significantly modify the effective noise, breaking the equivalence between the tasks and making noise estimation a highly sub-optimal strategy. In particular, whoever tests a new learning-based algorithm in comparison to a (variant of) KF with standard parameters tuning, essentially conducts an unfair comparison between an optimized algorithm and a non-optimized one. We suggest a method (based on Cholesky decomposition) to apply gradient-based optimization efficiently to the symmetric and positive-definite (SPD) parameters of KF, so that KF can be optimized similarly to common neural networks. The benefits of this method are demonstrated for both Radar tracking and video tracking. For Radar tracking we also show how a non-linear neural-network-based model can seem to reduce the tracking errors significantly compared to a KF - and how this reduction entirely vanishes once the KF is optimized. Through a detailed case-study, we also demonstrate that KF requires non-trivial design-decisions to be made, and that parameters optimization makes KF more robust to these decisions.