Hydrography is a subject of Geography. It concerns itself with measuring the physical characteristics of waters, such as rivers, lakes and oceans. It can also be about such measurement in navigable waters, as they are necessary for the safe passage of ships and vessels.
Massive hydrographical studies are usually undertaken by national or international organizations that sponsor data collection through surveys and publication of charts and descriptive materials for navigational purposes.
Hydrography's origin lies in the making of chart like drawings and notations made by individual mariners. It was usually a private property, even closely held secrets, used for commercial or military advantage.