Gilles (1688 - 1766) and Didier (c. 1723 - 1786) Robert de Vaugondy were map publishers, engravers, and cartographers active in Paris during the mid-18th century. The father and son team were the inheritors to the important Sanson cartographic firm whose stock supplied much of their initial material. Graduating from Sanson's map's Gilles, and more particularly Didier, began to produce their own substantial corpus of work. Vaugondys were well respected for the detail and accuracy of their maps in which they made excellent use of the considerable resources available in 18th century Paris to produce the most accurate and fantasy-free maps possible. The Vaugondys compiled each map based upon their own superior geographic knowledge, scholarly research, the journals of contemporary explorers and missionaries, and direct astronomical observation - moreover, unlike many cartographers of this period, they commonly took pains to reference their source material. Nevertheless, even in 18th century Paris geographical knowledge was severely limited - especially regarding those unexplored portions of the world, including the poles, the Pacific northwest of America, and the interior of Africa and South America. In these areas the Vaugondys, like their rivals De L'Isle and Buache, must be considered speculative geographers. Speculative geography was a genre of mapmaking that evolved in Europe, particularly Paris, in the middle to late 18th century. Cartographers in this genre would fill in unknown areas on their maps with speculations based upon their vast knowledge of cartography, personal geographical theories, and often dubious primary source material gathered by explorers and navigators. This approach, which attempted to use the known to validate the unknown, naturally engendered many rivalries. Vaugondy's feuds with other cartographers, most specifically Phillipe Buache, resulted in numerous conflicting papers being presented before the Academie des Sciences, of which both were members. The era of speculatively cartography effectively ended with the late 18th century explorations of Captain Cook, Jean Francois de Galaup de La Perouse, and George Vancouver.