[Public-list] depth sounder puzzle

[Rod Symmes]

Maybe it was like in the old WWII submarine movies.  There was an area in the creek where there was a boundary layer of water with drastically different temperatures or salinities and the sonar got a false echo.

Cheers,    Rod

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  ----- Original Message ----- 
  From: Gordon White 
  To: public-list at lists.alberg30.org 
  Sent: Monday, June 25, 2007 5:48 PM
  Subject: Re: [Public-list] depth sounder puzzle


  I was out this weekend for the first time this season and everything 
  seemed to work o.k - depth sounder, speed meter, auto pilot, etc. The 
  depth sounder has always been a foot on the conservative side - reads 
  six feet where there are actually seven from the surface. I checked this 
  in the slip with a pvc pole with a small plate on the end so it does not 
  go down in the mud and mislead me - Everything was fine.

      The depth readings just outside the slip were fine - 4.5 to 6 feet 
  (actual depths 5.6-7) but about 150 yards down the creek the depth 
  sounder began reading 1.5, 2. 1.5 feet. etc. Obviously it's not that 
  shallow or I'd have been pretty hard aground. The actual dept in that 
  stretch are 5.5 - 8 feet at that state of the tide.

      The shallow readings continued for 3/8 of a mile, then went back to 
  what they should be and remained o.k. all day until I rerturned and in 
  the same stretch of my creek (Moore's Creek off the Piakatank Rover)  I 
  got extremely shallow readings in the same stretch. It read accurately 
  when I got back in my slip.

  Anyone have any suggestions? At first I thought it was a glitch in the 
  instrument, but now I doubt that.

  - Gordon White
  Brigadoon II
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