If you observe having afavourite map projectionadelightfully geeky quirk , you ’re lead to want to raise a goner in honour of Jean - Félix Picard . Geodetics and cartography owe a debt of gratitude to the seventeenth century scientist who made the first exact measure of the Earth ’s sizing .
https://gizmodo.com/this-is-how-map-projections-warp-your-understanding-of-1499317119
Jean - Félix Picardwas born on this day in 1620 in La Flèche , France . He ’s deserving celebrate because in 1671 , he publishedMesure de la Terre , one of the first accurate measurements of the Earth ’s size . He negociate to measure the size of the Earth to within fractions of our current best - estimates using triangulation , maths , and a whole lot of forbearance .
Using triangulation to measure the breadth of a river in the sixteenth century . generator : Hulsius
Picard ’s not - so - secret technique was blend the preciseness of measuring distance with triangulation and the numerical genius of algebra and geometry .
He set out by very carefully measuring the spark length of a individual degree in latitude with harrowing precision with thirteen triangles along the summit between Paris and a clock tower in Amien . He dropped that into the kinship between radius and arc length for circles , jiggling around measured arc distance and the subtended slant to extract the wheel spoke of our satellite .
Here ’s the crazy bit : he measured the arc length of 1 academic degree line of latitude as 110.46 klick , thus calculated the planetary radius of 6,328.9 kilometers . Our current best mensuration of the polar radius * is 6,356.7 km . That ’s 0.44 % error , otherwise known as “ telling . ”
Like all scientists , Picard built on the study of those who came before * * . Francesco Maurolico bring out the basic cartoon of methodology in hisCosmographiain 1543 , while Willebrord Snellius made the first applied attempt by measuring out the distance between a pair of Dutch Town divide by a point latitude in 1615 . He published his results inEratosthenes Batavustwo years later , list the arc length as 107.395 km . While his technique was heavy , Picard ’s punctilious truth when follow the same methodology made the divergence between “ somewhat good ” and “ astonishing . ”
Happy birthday , Picard . Your forbearance and dedication to truth were admirable .
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- Polar radius matches up with the radius for an electric discharge segment subtend by latitude . You might be more intimate with the equatorial radius , which is the radius for an arc segment subtended by longitude , as that ’s how we typically compare the Earth to exoplanets .
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