robot_localization was the standard sensor fusion package for ROS. It was officially deprecated in September 2023. The designated replacement (fuse) still has no working GPS support two years later. FusionCore fills that gap: IMU, wheel encoders, and GPS fused via UKF at 100Hz on ROS 2 Jazzy. Automatic IMU bias estimation, Mahalanobis outlier rejection, adaptive noise covariance, TF validation at startup. Apache 2.0. Currently: 42 unit tests passing, Gazebo simulation working, 4 hardware testers running it this weekend including a farm robotics company doing RTK GPS fusion between corn rows with 3 inches of clearance, and a community contributor already submitted a PR adding PROJ-based coordinate system support. Happy to answer any technical questions.