Costmaps shows free space at grid_map as obstacles
I am trying to use rtabmap for navigation of quadcopter (from here) in Gazebo. Quadcopter is equipped with kinect. It hovers at a height of 1.5 m. Global and local costmaps both show that free space at grid_map in front of copter is occupied with obstacles. During the movement, these cells sometimes remain occupied, sometimes become free. Have I made any mistakes in rtabmap node or in .yaml files?
grid_map without global_costmap: