Category: Surveying

The list below is believed complete, though membership — like everything here — is subject to revision.

• Eight inches per mile, squared — The flat-Earth drop rule — a correct approximation of the Earth's curvature, cited chiefly by people who then fail to find it.
• Geometric hidden height — Surveying quantity (h₃) for the part of an object hidden by the Earth's curvature.
• Horizontal — The plane perpendicular to the plumb line — flat, and tangent to the level surface, but true only where it is taken; two distant horizontals are not parallel.
• Level — The geodetic sense of the word: a surface everywhere perpendicular to gravity, and therefore — over any distance — curved. Still water is the demonstration.
• Hamish Lorimer — Scottish surveyor (1803–1878) who devised the star-occultation method, found it measured only refraction, and abandoned it for cause.

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