English

Review of a hydrogra­phic survey that is directed toward evaluating compliance with, and the adequacy of, standards, rather than a careful examination of the data and their quality. The survey is carefully examined for adequacy with respect to data acquisition and confor­mance with applicable standards and project in­structions. In addition, the overall condition of the records and the Descriptive Report are examined. The digital data representing the survey is plotted and subjected to a cursory examination (spot check) to ensure that digi­tal data standards are being adhered to. The examina­ti­on of the survey data is limited only to that necessa­ry to evaluate the acquisition and processing procedu­res.

Hydrography is the branch of applied sciences which deals with the measurement and description of the physical features of oceans, seas, coastal areas, lakes and rivers, as well as with the prediction of their change over time, for the primary purpose of safety of navigation and in support of all other marine activities, including economic development, security and defence, scientific research, and environmental protection.

The scientific study of the waters of the EARTH, especially with relation to the effects of PRECIPITATION and evaporation upon the occur­rence and character of water in STREAMS, LAKES, and on or below the land surfaces.

METEOR consisting of an ensemble of liquid or solid water particles falling through or suspended in the ATMOSPHERE, blown by the WIND from the EARTH'S surface or de­po­sited on objects on the ground or in the free air.

An electroacous­tic TRANSDUCER that re­sponds to water-borne SOUND WAVES and delivers essenti­ally equivalent electric WAVES. See also PRESSURE HYDROPHONE.

A chain of separate receivers for seismic sound sources towed by a ship. The streamer contains many individual hydrophone elements and is divided electronically into a number of discrete sections or channels.

An instru­ment used to measure the EXTINCTION COEFFICIENT of transmission of light in water. It consists of a constant light source placed at a specific distance from a photocell. When placed in water, the electrical OUTPUT of the photocell is proportional to the amount of light striking the cell which, in turn, depends upon the transparency of the water. The instrument is calibrated to read 100 per­cent light transmission in air.