But When i check in rviz(above figure), In Frames > base_link > (Position & Orientation) values are the ground truth pose of the robot for map.
But When i typed in terminal like ( ros2 topic echo /tf ) , There’s only relative position & relative orientation values(Below figure) in that.
TF messages define offsets in terms of translation and rotation between different coordinate frames (parent-child schema). If you want to compute the transformation between no directly connected (at the first level) frames/links you can use the tf2 ROS/ROS2 library for that, particularly the lookup transform.
If you want to see a quick visualization of the transformation between two frames within Isaac Sim, you can try the following recently created external extension (particularly the Measuring tool) 😉