Cassini map

This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these messages) This article relies largely or entirely on a single source. Relevant discussion may be found on the talk page. Please help improve this article by introducing citations to additional sources. Find sources: "Cassini map" – news · newspapers · books · scholar · JSTOR (April 2020) You can help expand this article with text translated from the corresponding article in French. (March 2015) Click [show] for important translation instructions. View a machine-translated version of the French article. Machine translation, like DeepL or Google Translate, is a useful starting point for translations, but translators must revise errors as necessary and confirm that the translation is accurate, rather than simply copy-pasting machine-translated text into the English Wikipedia. Do not translate text that appears unreliable or low-quality. If possible, verify the text with references provided in the foreign-language article. You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation. A model attribution edit summary is Content in this edit is translated from the existing French Wikipedia article at [[:fr:Carte de Cassini]]; see its history for attribution. You may also add the template {{Translated|fr|Carte de Cassini}} to the talk page. For more guidance, see Wikipedia:Translation. (Learn how and when to remove this message)

The Cassini Map or Academy's Map is the first topographic and geometric map made of the Kingdom of France as a whole. It was compiled by the Cassini family, mainly César-François Cassini (Cassini III) and his son Jean-Dominique Cassini (Cassini IV) in the 1700s.

It was on a scale of one line to 100 toises, i.e. 1/86,400.

The map was, for the time, a real innovation and a decisive technical advance. It is the first map to be based on a geodesic triangulation. Four generations of the Cassini carried out the work, taking more than 6 decades to complete. The map does not precisely locate dwellings or the boundaries of swamps and forests, but the level of precision of the road network represented is such that by superimposing satellite photos onto map sheets of France, spectacular results are obtained.

The work of the Cassinis even left its mark on the land where today you can still find toponyms such as "Signal of Cassini." Such landmarks correspond to the corners of the triangles that formed the backbone of Cassini's map.

Nowadays, researchers frequently consult the Cassini map sheets, in its paper form in the reading room of the maps and plans department of the Bibliothèque nationale de France, or its digital form online.^{[1] [2]} It is of particular interest to archaeologists, architects, historians, geographers, genealogists, treasure hunters and ecologists who need to retrospect ecology or understand the history of landscape.

The genesis of the Cassini Map came during the reign of Louis XIV, with the creation of the Academy of Sciences alongside the ambitions of Jean-Baptiste Colbert for France's navy, the defence of her coasts and fixing the imprecision of the country's maps. At the time, distances between settlements to be portrayed on maps were often estimated by the time of the journey between them or by measuring the length of the road.^[3] Sometimes, triangulation was used - though often relying on the magnetic pin of a compass without concern for one's latitude.^[4] This would result in confounded errors when compiling these maps into one.^[4]

Cassini, alongside other scientists like Picard, Roëmer and Richer, investigated movement of the planets relative to Earth. Cassini noted such methods were riddled with instrumental errors and were susceptible to parallax.^[5] Picard and La Hire write in 1672 that King Louis XIV instructed the Academy of Sciences to, "create a map of all of France with the greatest precision possible.",^[6] Cassini writes that in September 1672, M. Vivier had, "come by order of the King" and was, "employed by order of the King to work on the Map of the Kingdom under the direction of the Academy of Sciences."^[6]

• French cartography

Online portal found here: https://www.geoportail.gouv.fr/donnees/carte-de-cassini