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# cour Geodesie physique - Ancient times Geodesy (6 century bc)

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44 pages
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cour Geodesie physique - Ancient times Geodesy (6 century bc)

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 Publié par Nombre de lectures 167 Langue Français Poids de l'ouvrage 9 Mo

Exrait

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=> no horizon
Ancient times Geodesy (6 century bc)
eThglanαoethfuseilnthgeridD>=noitceridlacethnodsenepsnoepdnnedtcoiertialvloctheric=craE:ht0°36/edfotehalituteofthesiteSiz
At one place on Earth, the Sun is vertical (lights the bottom of a well) only once a year
α* d12 km= 40000
At the same time, at a different place, the Sun is not vertical The angle can be measured from the length of the shadow of a vertical pole
Ancient times Geodesy (Eratosthene, 300 bc)
«Modern»
Geodesy (17th century)
A correction has to be made if distance isnot aligned with longitude
d12can be computed from thesum(oriented) of many smaller distances
Measuring many (if not all) distancesandangles within a network of points give the more accurate solution for d12
The shape of the Earth (18th century)
Making those measurements, different people find different values for the length of an arc ofat different places in Europe - Snellius (1617) : 104 km - Norwood (1635) : 109 km - Riccioli (1661) : 119 km
In France,Picardfinds : - 108 kmin thenorthof France - 110 kmin thesouthof France
d1
α
α
< d1d2
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