Using wheel encoders and IMU with robot_localization

Hi all, I am using wheel_encoders which is giving odometry information of the type `nav_msgs/Odometry` and IMU which gives `sensor_msgs/IMU` (IMU is giving orientation, angular velocity and linear acceleration). I am using them with [robot_localization](http://wiki.ros.org/robot_localization). It seems to be working but when I save a bag file and then run it and visualize the odom (from the `wheel_encoders`) and the odometry output of `robot_localization`, they seem off under the settings shown in the launch file below. Here is the link to the [video](https://youtu.be/4k5htqfe3i0) (Red arrow represents odometry from `wheel_encoders` and Blue arrow represents output odometry from `robot_localization`). **ekf_robot_localization.launch** [false,false, false, false, false, false, true, true, false, false, false, true, false, false, false][false, false, false, false, false, false, false, false, false, false, false, true, false, false, false][0.05, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.05, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.06, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.03, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.03, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.06, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.025, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.025, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.04, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.015][1e-9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e-9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e+9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e+9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e+9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e-9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e-9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e-9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e+9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e+9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e+9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e-9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e+9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e+9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1e+9] In the above case, `wheel_encoders` odometry and output filtered odometry of `robot_localization` is off meaning they diverge. Is this behavior normal? Also, If I use x,y,yaw from `wheel_encoders` odometry (`differential = false`) and vyaw from IMU (differential = false), odometry from `wheel_encoders` overlaps perfectly with the output of `robot_localization`. Also, If I just use `wheel_encoders` odometry in `robot_localization` (no IMU), its odometry overlaps perfectly with the odometry output of `robot_localization` (obviously). I am just trying to understand why is this happening and what is causing it and what are best settings for the above case? Can someone pitch in with their ideas? Thanks in advance. Naman Kumar