The Greeks studied the results of the measurements of latitude by the explorer Pytheas who voyaged to Britain and beyond, as far as the Arctic Circle (observing the midnight sun), in 325 BC. They used several methods to measure latitude, including the height of the Sun above the horizon at midday, measured using a gnōmōn (a word that originally meant an interpreter or judge); the length of the day at the summer solstice, and the elevation of the Sun at winter solstice. The Greek Marinus of Tyre (AD 70–130) was the first to assign a latitude and longitude to every place on his maps.