Navigation is the methods used to learn where someone is and how to go to another place. Since this is easy when landmarks are visible, the word is often limited to the methods ships or aircraft use. The word "navigation" was invented in the 15th century from the Latin word "navis" which means "ship" and is found in other Indo-European languages. Navigation is literally "art of ship mastery" but is also used for 'finding one's way'. The Global Positioning System is the main tool for it.