sex·tant
noun/ˈsekstənt/
/ˈsekstənt/
- an instrument for measuring angles and distances, used to calculate the exact position of a ship or an aircraft
六分仪（用以计算船舶或飞机的准确位置） Word Originlate 16th cent. (denoting the sixth part of a circle): from Latin sextans, sextant- ‘sixth part’, from sextus ‘sixth’.