Hydrography, << hy DROG ruh fee, >> is the branch of physical geography that deals with the surface waters of the earth, especially with regard to navigation. Hydrographers make surveys of navigable water, including oceans, rivers, and lakes. They publish charts and maps that show wafter depths and the position of coastlines, channels, reefs, and shoals. Hydrographers also study tides, currents, and winds.
Most countries have developed well-organized hydrographic agencies. Hydrographic work in the United States is carried on by the National Oceanic and Atmospheric Administration, by the Naval Oceanographic Office, and by the Corps of Engineers of the Army. Canada maintains a hydrographic service as part of Fisheries and Oceans Canada.
