What system of navigation in which a navigator finds positions of measure would christopher columbus use?

Celestial navigation or the use of the sun, the moon and stars.

"Celestial navigation is the use of angular measurements (sights) between celestial bodies and the visible horizon to locate one's position on the globe, on land as well as at sea. At a given time, any celestial body is located directly over one point on the Earth's surface. The latitude and longitude of that point is known as the celestial body's geographic position (GP), the location of which can be determined from tables in the Nautical or Air Almanac for that year."