Old instruments
Latitude by Meridian Altitude
Direct answer
Latitude by Meridian Altitude is a latitude calculation using a body's corrected altitude when it crosses the observer's meridian and its declination.
Latitude by Meridian Altitude is a noon-or-transit latitude method used in historical astronomy, timekeeping, or navigation.
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At a glance
- Found in
- Historical Almanacs & Instruments
- Related
- Celestial Navigation, Dead Reckoning, Longitude by Chronometer, Noon Sight
Latitude by Meridian Altitude is a noon-or-transit latitude method used in historical astronomy, timekeeping, or navigation.
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The story behind Latitude by Meridian Altitude
Meridian altitudes of the Sun and stars were among the most enduring practical latitude methods.
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Why Latitude by Meridian Altitude matters
Latitude by Meridian Altitude matters because meridian geometry reduces the problem to the relationship among zenith distance, declination, and latitude.
How to read Latitude by Meridian Altitude
Read Latitude by Meridian Altitude by identifying upper or lower transit, correcting the altitude, and applying the correct same-name or contrary-name rule.
Latitude by Meridian Altitude in practice: an example
At upper transit, ninety degrees minus corrected altitude gives zenith distance for combination with declination.
Where readings of Latitude by Meridian Altitude go wrong
A near-noon sight is not automatically the exact meridian altitude, and a wrong declination sign reverses the result.
Sources and editorial method
Research references used for this entry include:
- National Geospatial-Intelligence Agency: The American Practical Navigator - Official modern reference for navigation principles, celestial observations, sight reduction, and navigational tables.
- U.S. Naval Observatory: Astronomical and Navigational Almanacs - Official descriptions of the Astronomical Almanac, Nautical Almanac, and their tabular data.
- Source
- The Great Almanac Dictionary
- Category
- Historical Almanacs & Instruments
- Last updated
- 2026-09-26
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More in Historical Almanacs & Instruments
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Common questions
What is Latitude by Meridian Altitude?
Latitude by Meridian Altitude is a latitude calculation using a body's corrected altitude when it crosses the observer's meridian and its declination.
What do people get wrong about Latitude by Meridian Altitude?
A near-noon sight is not automatically the exact meridian altitude, and a wrong declination sign reverses the result.
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