Joseph Teulère's efforts in the late eighteenth century were not confined to raising Cordouan. He improved navigation along the "river of Bordeaux" thanks to hydrographic surveys and the construction of artificial daymarks indicating the straits and the routes to follow. In the 1820s, more coastal surveys were carried out under the leadership of the father of modern hydrography, Charles-François Beautemps-Beaupré. In the course of the nineteenth century, the arrival of the steam engine – on both land and sea – accelerated the flow of transport. This increased calls by sailors for the government to improve both lighting and markers. The estuary and straits had to be made navigable by both day and night. Two lights were built at Grave (1823) and La Coubre (1830) to indicate the boundaries of the estuary. They were constantly improved, strengthened and rebuilt over the course of the nineteenth century. Royan and its environs were also indicated by a light at Terre Nègre (1838) and a port signal (1823). Saint-Georges de Didonne and Suzac (1860) provided alignments, as did Chay and Saint-Pierre de Royan (1873). These land-based lights were completed by lightships, and then, at the turn of the century, by lighted buoys. In 1901, a surprising small estuary lighthouse, Trompeloup, was erected, which formed an alignment with the light on the island of Patiras. Ongoing efforts to mark the waterway explain the diversity of structures, of which Cordouan became, over the course of the nineteenth century, the "ancestor".
