section_path: Commerce and travel
section_name: Commerce and travel
paragraph_text: Commerce and travel
  
  Apart from the Nile, Tigris, and Euphrates, navigable rivers were uncommon in the Middle East, so transport by sea was very important. Navigational sciences were highly developed, making use of a rudimentary sextant (known as a kamal). When combined with detailed maps of the period, sailors were able to sail across oceans rather than skirt along the coast. Muslim sailors were also responsible for reintroducing large, three-masted merchant vessels to the Mediterranean. The name caravel may derive from an earlier Arab boat known as the qarib.
  
  Many Muslims went to China to trade, and these Muslims began to have a great economic influence on the country. Muslims virtually dominated the import/export industry by the time of the Song dynasty (960–1279). Muhammad al-Idrisi created the Tabula Rogeriana, the best maps of the Middle Ages, used by various explorers such as Christopher Columbus and Vasco Da Gama for their voyages in America and India.