Navigation and Seamanship (1+1)

3.1.5. Introduction to Echosounder

                                                                           

Lead lines were used to measure the sea water depths before the invention of echosounders . This technique was generally called as sounding. The echosounding principles were used to detect iceberg by the Canadian engineer R. A. Fessenden in 1914. During the World War II echosounders were played major role in detection of submarines. In 1954 an advanced, highly accurate echo sounder called the Precision Depth Recorder (PDR) was developed. Since World War II echosounders have been used to determine water depth in the oceans. Echo sounders, sometimes called fathometers, are used by vessels for navigational purposes, not only to avoid shoal water but as an aid in fixing position when a good bathymetric chart of the area is available

Development of Acoustic Methods in Fisheries

An acoustic method for the detection of fish was first attempted by Kimura in 1929. This technique gained importance after the invention of paper recording of echo-sounder by Wood et al., (1935). The application of echo-sounders to fishing occurred after World War II and they were also used for the fish biomass estimation. For the next stage of development, attempts were made to count and size fish from their echoes. The commercial fishing vessels were started using the acoustic instruments only during early 1950’s. The echosounder was used for measuring the depth of water and to find the fish beneath the vessel . When the echosounder used in fishing vessels then it is called as fish finder (also called a depth finder / sounder / Fish finder / Depth recorded ). In fisheries the term echosounding (vertical sounding) is usually restricted to sound transmitted from a vessel and returned to it along a line straight down to the sea bed (or bottom). The equipment employing this technique is called an ECHOSOUNDER.