Deleting objects on the map

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I'm new to ROS and I'm dealing with the navigation stack right now. I need to solve the simplest problem of moving from point A to point B with a detour of obstacles. As a matter of fact, I implemented this using move_base, but I ran into the problem that objects written to global costmap are not deleted, even if the laser does not detect them. I know that if the laser sees something behind the object, it will remove it, but my robot will work in an open field.