Category: Geodesy

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

• 180-degree plane – Claim that the equator is a 90-radian circle forming one flat plane that contains all land.
• George Biddell Airy – The Astronomer Royal whose 1871 aether experiment was rebranded 'Airy's failure' and conscripted, posthumously and without consent, as a flat-earth proof.
• Cornelis Baak – Dutch metrologist (1838–1911) who held that a dispute lasts only until the disputed quantity is measured finely enough, and built three instruments that proved it did not.
• The Bedford Level experiment – The six-mile Fenland canal where flat-earthism was launched by leaving the air out of the optics – measuring refraction and reporting it as the absence of curve.
• Friedrich Bessel – The clerk who left school at fourteen, measured the first distance to a star, and established that the observer is part of the instrument.
• Cartography – The making of flat maps of a surface that is not flat.
• Circle – The set of points at one fixed distance from one point. A curve, not the region it encloses, and the definition several doctrines here decline to read.
• Deflection of the vertical – Down does not point at the centre of the Earth. The plumb line leans towards whatever rock is nearby, by a few seconds of arc, and the lean is a map.
• Dip of the horizon – The angle by which the sea horizon falls below eye level, growing as the square root of the observer's height: in every almanac, and shaped like a radius.
• Earth – The third planet, and the one thing every other article here is about: an oblate spheroid since antiquity, flattened and taken personally ever since.
• 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.
• Eratosthenes – Greek polymath (c. 276–194 BC) who measured the Earth's circumference to within a few percent – the figure whole-radian geometry declines to address.
• The figure of the Earth – The measured shape of the planet, and the long labour of measuring it.
• Flat – Of no curvature anywhere – a plane. A stronger condition than 'level' or 'horizontal': a tilted floor is flat but not level, and still water is level but not flat.
• 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.
• Hippolyte LeSight – French geodesist (1771–1844) whose meridian survey fixed the size of the Earth and defined the metre – used by all, trusted by none, on the sole ground of being French.
• 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.
• Nevil Maskelyne – Fifth Astronomer Royal, remembered as the man who cheated John Harrison. He ran the trial in question, and it beat his own method by three to one.
• Nautical mile – A minute of the world, rounded off: the unit named for a minute of latitude, which had to stop being one before it could be used.
• The Schiehallion experiment – The 1774 measurement that weighed the Earth by how far a Scottish mountain pulled a plumb-line sideways – and invented the contour map doing it.
• Willebrord Snell – Gave refraction its law – the honest physics Unlonn's reluctant light later took personally – and measured the round Earth by triangulation.
• Sphere – The set of points at one fixed distance from one point in space. A surface, not the solid it bounds, and no part of it will lie flat.
• Surveying – Plane surveying ignores the Earth's curvature up to about a hundred square miles. That is a tolerance with a number on it, not an opinion about the shape.
• Value of one radian – The doctrinal claim that one radian is 57.30 nautical miles, obtained from 360 ÷ 2π.
• Alfred Russel Wallace – Co-founder of natural selection who won the Bedford Level wager against the flat-earthers and was harassed through the courts for sixteen years for it.
• Whole-radian geometry – Discredited system in which a circle holds 360 radians, a radian is a distance, and a turn is 4π.

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