Eitan, Thanks for your reply. You are right that the warning message refers to something wrong in the laser filters. What I found is in the source file sac_inc_ground_removal_standalone.cpp, there are a few default settings for PR2 robot, such as the robot_footprint_frame is "base_footprint" the laser_tilt_mount_frame is "laser_tilt_mount_link" the goal frame id for point cloud is "odom_combined" and the function updateParametersFromServer() in fact doesn't update the above parameters. So I changed the codes for our own robot accordingly, and the sac_inc_ground_removal_node node now runs properly! Yet the result of topic /ground_object_cloud looks not so perfect, i.e., there are part of the ground close to the robot still left within the point cloud of this topic. I also observed that in the output of tilt_scan_shadow_filtered, the ground plane is not exactly in horizontal level but looks more like a slope. So I guess this means the tilt controller need further calibration to make sure its "0" position refers to the true horizontal plane. How did you handle this issue for PR2 robot? thanks xiaojun -- View this message in context: http://ros-users.122217.n3.nabble.com/Navigation-stack-issue-about-ground-plane-detection-tp1707477p1739332.html Sent from the ROS-Users mailing list archive at Nabble.com.