"Echometre" record from S. S. De Grasse.
Crossing over canyon near Georges Bank.
Bulletin 4 of the Association of Field Engineers, Dec. 1931, p. 83
Image ID: theb2157, NOAA's Historic Coast & Geodetic Survey (C&GS) Collection
Credit: Association of Commissioned Officers
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of the U.S. Department of Commerce, National Oceanic & Atmospheric
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