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Old 03-19-2018, 04:58 PM   #4
markpierce
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City: Vallejo CA
Vessel Name: Carquinez Coot
Vessel Model: penultimate Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 12,559
It is distance over seabed versus distance through water. Difference would be due to water currents assuming instruments are 100 percent accurate.
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