1. A geographic positioning system, comprising: a data source providing topographical information about at least a portion of a surface of earth, including topographical information about contours of a surface of at least a portion of a body of water on the earth, the topographical information correlating the contours with geographic locations on the earth; a sensor configured to detect a contour of a portion of the surface of the earth; and a contour matching engine coupled to the data source and to the sensor and configured to automatically match the detected contour to a contour provided by the data source and automatically provide a geographic location of the detected contour.