Source : Webster's Revised Unabridged Dictionary (1913)

Hydrography \Hy*drog"ra*phy\, n. [Hydro-, 1 + -graphy: cf. F.
   hydrographie.]
   1. The art of measuring and describing the sea, lakes,
      rivers, and other waters, with their phenomena.

   2. That branch of surveying which embraces the determination
      of the contour of the bottom of a harbor or other sheet of
      water, the depth of soundings, the position of channels
      and shoals, with the construction of charts exhibiting
      these particulars.

Source : WordNet®

hydrography
     n : the science of the measurement and description and mapping
         of the surface waters of the earth with special reference
         to navigation