The ______ of a point has been measured for thousands of years by mariners and land travelers by observing the ______ of Polaris, the north star.

• A. latitude, altitude
• B. longitude, altitude
• C. latitude, azimuth
• D. declination, altitude

Answer: (A)

Latitude is determined by the altitude of Polaris. Since Polaris lies almost directly above the North Celestial Pole, the angle of Polaris above the horizon equals the observer’s latitude in degrees. This simple relationship let mariners and travelers measure how far north they are for thousands of years by observing Polaris’s altitude. The azimuth—its compass direction—doesn’t provide latitude, and declination is a fixed celestial coordinate for the star that doesn’t reflect the observer’s location.