The inception of aerial photography as an aid to mapping in Haiti arose from the desire of the Travaux Publics to secure as quickly as possible an accurate map of the Arlibonite Valley. It is the largest single valley in Haiti, the most fertile, and the best adapted to irrigation as the largest river in the republic runs through one side of it. After bringing down silt for centuries, the river has gradually raised the land through which it flows until its course is now higher than the rest of the valley. The valley was intensively cultivated and partially irrigated by the French in colonial times. The long, straight and, in many cases, parallel roadways and section lines covering the valley today like a network, show the thoroughness or the colonists’ work. Now the valley lies dormant, grown to seed, yet with many little cultivated patches, scattered about here and there, with clusters of huts near by. There is a sharp contrast between the overgrown roadways with their jungle slothfulness, and the white man’s thrift and orderliness.