Common Use
As well as an aid to navigation (most larger vessels will have at least a simple depth sounder), echo sounding is commonly used for fishing. Variations in elevation often represent places where fish congregate. Schools of fish will also register. Most charted ocean depths use an average or standard sound speed. Where greater accuracy is required average and even seasonal standards may be applied to ocean regions. For high accuracy depths, usually restricted to special purpose or scientific surveys, a sensor may be lowered to observe the factors (temperature, pressure and salinity) used to calculate sound speed and thus determine the actual sound speed in the local water column. This latter technique is regularly used by US Office of Coast Survey for navigational surveys of US coastal waters. See NOAA Field Procedures Manual, Office of Coast Survey website (http://www.nauticalcharts.noaa.gov/hsd/fpm/fpm.htm).
Read more about this topic: Echo Sounding
Famous quotes containing the word common:
“... a nation to be strong, must be united; to be united, must be equal in condition; to be equal in condition, must be similar in habits and feeling; to be similar in habits and feeling, must be raised in national institutions as the children of a common family, and citizens of a common country.”
—Frances Wright (1795–1852)
“The object of government in peace and in war is not the glory of rulers or of races, but the happiness of the common man.”
—William, Lord Beveridge (1879–1963)