OSS + ELC EU 2026

EKF2 is the heart of PX4's navigation, and over the past few years it has quietly received a series of improvements that make it more accurate, more robust, and easier to work with. In this talk I'll walk through the most significant ones. We'll start with a short recap of the filter's architecture, then cover the move to a proper error-state formulation, along with its symbolic derivation and code generation using SymForce. We'll then see how this makes it easy to add a new state or measurement, as we did for the terrain state. From there we'll turn to round-earth navigation, paired with a position-dependent gravity model, which replaces the flat-earth assumptions to support long-range and high-latitude flight. We'll also look at how the Joseph-stabilized covariance update not only makes the filter more numerically stable, but also lets us perform partial updates, which we rely on heavily in the magnetometer and optical-flow fusion. Finally, we'll look ahead at the next changes coming to EKF2 and some of the ideas we're exploring.