Bathymetry
Bathymetry is the study of the underwater terrain of lakes or ocean floors. It is the same as topography, except that it looks at the underwater topography. It is a field of oceanography. The name comes from Greek βαθύς (bathus), meaning "deep",[1] and μέτρον (metron), meaning "measure".[2] Bathymetric (or hydrographic) charts are often made to support the safety of underwater navigation and exploration. Most of these underwater topographic maps use contour lines (called depth contours or isobaths) to show the terrain of the sea floor, and how deep it is. They usually also give surface navigational information.
Originally, bathymetry involved the measurement of ocean depth through sounding. Early techniques used heavy rope or cable lowered over a ship's side. This method measures the depth of the water at a single location each time. It was not a very accurate method. The data used to make bathymetric maps today usually comes from an echosounder (sonar). This device is attached to the bottom or the side of a boat.[3]
Bathymetry Media
Bathymetry of the ocean floor showing the continental shelves and oceanic plateaus (red), the mid-ocean ridges (yellow-green) and the abyssal plains (blue to purple) 
Methane venting offshore Virginia
A seafloor map captured by NASA
First printed map of oceanic bathymetry, published by Matthew Fontaine Maury with data from USS Dolphin (1853)
The seafloor topography near the Puerto Rico Trench
STL 3D model of Earth without liquid water with 20× elevation exaggeration
A three-dimensional echo sounding map
References
Other websites
- High resolution bathymetry for the Great Barrier Reef and Coral Sea Archived 2010-10-04 at the Wayback Machine
