hydrography
n. நிலவுலக நீர்நிலைப் பரப்பாராய்ச்சித்துறை.
Hy*drog"ra*phy, n. Etym: [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.