Fathometer definitions

Fathometer

1) Depth finder 2) Sonic depth finder
Found on https://www.crosswordclues.com/clue/fathometer

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fathometer

instrument for measuring underwater depth using sound
Found on http://phrontistery.info/f.html

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Fathometer

trade name for a type of sonic depth finder (q.v.).
Found on http://www.britannica.com/eb/a-z/f/11

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