What method is used to interpret observed and calculated height in navigation?

The Altitude-Intercept Method is employed to interpret observed and calculated heights in navigation primarily because it provides a systematic approach for determining a vessel's position based on celestial observations. This method utilizes the angle of elevation— or altitude— of celestial bodies, such as the sun, moon, planets, and stars, to establish the navigator's latitude and longitude.

In this context, the navigator takes sightings of celestial bodies and measures their altitudes above the horizon. These observed altitudes are then compared to the corrected, or calculated, altitudes of the celestial bodies as predicted by nautical almanacs and ephemerides. The discrepancies between the observed and calculated heights allow navigators to compute a line of position, which is essential for determining their current location on the earth’s surface.

The Altitude-Intercept Method is favored for its accuracy and reliability making it a fundamental technique in celestial navigation, allowing navigators to effectively cross-check their positions and enhance the safety and efficiency of their voyages.