In the 18th century the science of surveying made rapid advances, and many countries were completely overlaid with triangles, using the surveying method of triangulation. In the United Kingdom of the Netherlands such a survey was partially completed by general Krayenhoff, but the Belgian Revolution prevented its completion in Belgium. Craan helped to give new impetus to this effort. His main contribution was his "Plan géométrique de la ville de Bruxelles avec ses faubourgs et communes limitrophes" (in 4 folios, 1836). He had made the measurements for this city plan already in 1821.