I have built an occupancy map using the gmapping package in ROS for a (real) hallway. Now I want to use this map in Gazebo so that I can simulate my robot in this environment. It seems that Gazebo can only support the map built from its own models, not from an external occupancy map. Is there any way that I can use an occupancy map in Gazebo or some other simulators? It is easier to obtain an occupancy map from real world than building a physical world in a simulator...