Lighthouses 16 Month 2012 Calendar. Primarily used as an aid for navigation and pilotage at sea, Lighthouses are buildings which send sending out beams of light using a system of lamps and lenses to warm approaching vessels of the impending danger that lays ahead. Most often they are located around rocky shores and entrances to ports and harbours. Until recently, lighthouses were manned, but nowadays they are computer controlled and their numbers are seriously in decline due to the introduction of modern navigational aids. It is though that the number of operational lighthouses now stands at less than 1,500 worldwide. Britain, being an island nation supports many of these remaining lighthouses.