odom and base_link frames are far - localization
I have an imu and gps only and i want use them for localization. I am using robot_localization ekf node. its setting is similar to this. when I view the tf on rviz, odom tf and base_link tf are far away from each other. I do not understand why?
1) why they are far from each other?
2) how to make sure that my robot is localizing correctly?
3) I do not understand how gps's data and odom are related. like when I view it on rviz odom will be at origin right? but how it is related to the gps coordinates?