Helipads are common features at hospitals where they serve to facilitate medical evacuation or air ambulance transfers of patients to trauma centers or to accept patients from remote areas without local hospitals or facilities capable of providing the level of emergency medicine required. In urban environments, these heliports are typically located on the roof of the hospital. Rooftop helipads sometimes display a large two-digit number, representing the weight limit (in thousands of pounds) of the pad. In addition, a second number may be present, representing the maximum rotor diameter in feet.[3] Location identifiers are often, but not always, issued for helipads. They may be issued by the appropriate aviation authority. Authorized agencies include the Federal Aviation Administration in the United States, Transport Canada in Canada, the International Civil Aviation Organization, and the International Air Transport Association. Some helipads may have location identifiers from multiple sources, and these identifiers may be of different format and name
