State Estimator component in Aerostack2 is the one in charge get the pose and twist of the drone. For that, is use the information provided by the sensors and the information provided by the platform.
Also, it is in charge of generate the ROS 2 Tf2 tree, so the rest of the components can consult it. For that, it stablish a common earth frame for all drones and set the map and odom frames of each one.