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:
“The moment the very name of Ireland is mentioned, the English seem to bid adieu to common feeling, common prudence, and common sense, and to act with the barbarity of tyrants, and the fatuity of idiots.”
—Sydney Smith (1771–1845)
“The common notions that we find in credit around us and infused into our souls by our fathers’ seed, these seem to be the universal and natural ones. Whence it comes to pass that what is off the hinges of custom, people believe to be off the hinges of reason.”
—Michel de Montaigne (1533–1592)