 It was important to survey the extent of the Abrolhos Archipelago reefs, shown incorrectly in Roussin's survey, then proceed to Rio de Janeiro to decide the exact longitude of Villegagnon Island.The real work of the survey was then to commence south of the Río de la Plata, with return trips to Montevideo for supplies; details were given of priorities, including surveying Tierra del Fuego and approaches to harbours on the Falkland Islands.The west coast was then to be surveyed as far north as time and resources permitted.