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 person of definite character and purpose who comprehends our way of thought is sure to exert power over us. He cannot altogether be resisted; because, if he understands us, he can make us understand him, through the word, the look, or other symbol, which both of us connect with the common sentiment or idea; and thus by communicating an impulse he can move the will.”
—Charles Horton Cooley (1864–1929)
“The common breeds the common,
A lout begets a lout,
So when I take on half a score
I knock their heads about.”
—William Butler Yeats (1865–1939)