Yourbestsailvideo
Introduction to celestial navigation (Lesson 1)
October 23, 2023 · 16 min · 8K views
What this video covers
Celestial navigation determines a vessel's position by measuring the altitude of a celestial body, such as the Sun, rather than relying on electronic GPS.0:16 The process requires a nautical almanac to identify the body's geographic position—its latitude and longitude—at a specific time.2:33 Because the Earth is a sphere, measuring the zenith distance (the angle between the observer's vertical and the celestial body) defines a circle of position on the globe.5:55 Since measuring the zenith distance directly is difficult without a clear reference for the vertical, navigators use a sextant to measure the body's altitude above the horizon.7:17
Because standard nautical charts cannot display these large-scale circles of position, navigators use the intercept method to plot lines of position.9:07 By comparing an estimated position to the observed altitude, the navigator calculates a delta-altitude, which represents the distance from the estimated point to the actual line of position.12:27 Intersecting two or more of these lines provides a fix.13:59 The simplest application of this theory is the meridian altitude of the Sun, which allows for a direct calculation of latitude.14:27
More from Yourbestsail
From Yourbestsail — see the channel’s boat, crew, and every analyzed video.
The Sailing Directory Newsletter
One email with the fleet's best finds — the moments, boats, and stories worth your watch time. Enter your own address to get your own copy.