Final answer:
An explorer would use a sextant to measure the angle between a celestial object and the horizon, allowing them to determine their latitude and longitude on a map.
Step-by-step explanation:
An explorer would use a sextant to determine their position on a map by measuring the angle between a celestial object (such as the sun or a star) and the horizon. By knowing the exact time of the observation and consulting tables, the explorer can calculate their latitude and longitude. This method is known as celestial navigation and was widely used by early explorers before the advent of modern technology.
Learn more about Using a sextant for celestial navigation