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Wndsn Expedition Team

Ex Mensura, Scientia

Wndsn Dipping Distance Calculator

High-precision dipping distance calculator. Companion to Wndsn Telemeters: Low tech, high utility graphical distance & altitude computers from the Wndsn applied science lab.

Dipping distance is the distance at which a lighthouse or other object just becomes visible to an observer over the horizon due to the Earth's curvature.

Calculate dipping distance.

The heights on both sides of the horizon.

Input

Determine distance d for h1 and h2 (use ft or m)
Reset

Results

  • Height of the observer: h1 = 4 m or 13.1 ft
  • Height of the lighthouse: h2 = 49 m or 160.8 ft
  • Distance to the horizon: d = 7.7 km or 4.2 nm or 4.8 mi
  • Distance to the lighthouse: d = 34.7 km or 18.7 nm or 21.5 mi

The display precision set is .1. To change that, edit the variable &digits=x in the URL where 0 <= x <= 9.

Explanation

[Load sample values (JSON) (XML) (CSV).]

Distance in nautical miles = 2.08 · (√h1 + √h2). Note that the value 2.08 accounts for average atmospheric refraction.

Setting h2 = 0 returns the distance to the horizon.

Reference

1     km = 0.539 nm = 0.621 mi
1.852 km = 1     nm = 1.151 mi
1.609 km = 0.869 nm = 1     mi

Kilometers, nautical miles, and statute miles.

See also