Fusing absolute position information and IMU-data using the ekf_localization_node

Hello, I have a robot car with a laser-scanner and an imu and would like to fuse the position information of the two sensors. For laser based localization I am using the hector_mapping node which produces a /poseupdate topic. Additionally I am using and imu producing the /imu/data topic. Those two shall be fused to provide a more accurate position estimate at a higher rate. The launch files look like this: [true, true, true, true, true, true, false, false, false, false, false, false, false, false, false] [false, false, false, true, true, true, false, false, false, true, true, true, true, true, true] I am not totally sure about the frame configuration for hector_mapping and ekf_localization_node. The programm runs with the settings above however the odom frame is drifting away in a constant direction with moderate speed. For validating the operation of ekf I tried setting the imu covariance to a very small value of 1e-10 i.e. relying only on imu-data). However like this the baselink-frame only seems to use orientation information from the imu and does not move when appyling acceleration on the imu. Here is the tf-tree:  Thank you.