Old instruments
Dip Correction
Direct answer
Dip Correction is the correction for the visible sea horizon lying below the observer's true horizontal plane.
Dip Correction is a height-of-eye horizon correction used in historical astronomy, timekeeping, or navigation.
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At a glance
- Found in
- Historical Almanacs & Instruments
- Related
- Computed Altitude, Altitude Correction, Refraction Correction, Semidiameter Correction
Dip Correction is a height-of-eye horizon correction used in historical astronomy, timekeeping, or navigation.
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The story behind Dip Correction
Dip tables became routine companions to marine sextant observations from elevated decks.
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Why Dip Correction matters
Dip Correction matters because greater height of eye increases the depression of the horizon and therefore changes the measured altitude.
Dip Correction in practice: an example
A bridge-wing sight applies a larger dip magnitude than the same sight taken close to sea level.
Where readings of Dip Correction go wrong
Dip for a natural sea horizon is not the same as an artificial-horizon or bubble-sextant correction.
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.
- 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 Dip Correction?
Dip Correction is the correction for the visible sea horizon lying below the observer's true horizontal plane.
What do people get wrong about Dip Correction?
Dip for a natural sea horizon is not the same as an artificial-horizon or bubble-sextant correction.
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