Maps exert power. In this paper I explore the power of maps in relation to the technical methods employed and the political context of their production. The internal power of maps is realised in the actions taken by cartographers themselves when making maps, while the external power of maps is both realised by the patrons of cartography and wielded through the use of cartographic products as agents for natural resource management, in particular for defining conservation strategies. An Australian case study of coastal mapping is used to examine the methods employed and motivation behind map production through a series of recent remote sensing initiatives to map Lord Howe Island, New South Wales. Through this case study I explore the subjectivities associated with the placement of boundaries in the scientific practice of cartography. I argue that a new epistemological reading of maps is necessary, as sources of information on socio-politically constructed worlds as much as the phenomenological world of objects. Such a reading is particularly important given recent advances in technologies, such as remote sensing, that are increasingly used to inform coastal management, and which propagate in profound new ways the power of maps.