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Yachtmaster Ocean revision module 5 of 10

NOON

Meridian Altitude and Latitude

Noon sights, meridian passage, declination, observed altitude, and latitude by sun.

meridian altitudenoon sight

3 guided lessons · 8 practice questions · 8 flashcards

3 outcomes · self-guided revision
  • Explain noon sights, meridian passage, declination, observed altitude, and latitude by sun.
  • Apply meridian altitude to a realistic onboard situation.
  • Recall the core check: meridian altitude gives latitude.

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Lesson routeNoon Sight Purpose0/1 read

Lesson 1 of 1

Noon Sight Purpose

A meridian altitude sight uses the body's maximum altitude as it crosses the observer's meridian. With the Sun, this is the classic noon sight. It is a robust way to find latitude when longitude/time is less certain.

The idea is simple: corrected altitude gives zenith distance, and zenith distance combined with declination gives latitude. The signs depend on whether the body and observer are north or south of the equator and whether the body is north or south of the observer.

  • Meridian altitude gives latitude.
  • Maximum altitude occurs at meridian passage.
  • Zenith distance is 90 degrees minus observed altitude.
  • Declination sign and hemisphere must be handled carefully.
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