These models were created as a part of Cargo-ANTS project which required a simulation environment of a container terminal scenario. So many harbour entities were created using freely available Google sketchup models like ship, idle_truck, containers, straddle_carriers, etc. Note: These models are simple sdf models and not URDF models and do not have dynamic engine. Feel free to use these models and please cite the following paper: Local Path Optimizer for an Autonomous Truck in a Harbour Scenario J David, R PHILIPPSEN, R VALENCIA, K Iagnemma - 11th Conference on Field and Service Robotics (FSR), Zurich 2017.
Keep the models along with your other Gazebo models or edit your gazebo/setup.sh to include this file location.