On Sat, 19 Mar 2005 08:54:24 GMT, "Dennis Pogson"
wrote:

Mark wrote:
Also make sure you can OFFSET the reading, too. . . . you want
to be
able to calibrate in the depth difference offset from the transducer's
location to the bottom of the keel.

Two schools of thought here; the "make it read 0 when the keel
touches" and the "make it read the actual depth, 0 equals no water."
The lattter seems more common, easier to correlate the depth to chart
soundings and what other folks say the depth is. To each his own
though.

Any depth sounder that will read to 50' is deep enough. . . .
Who cares if the
depth is 3000' or 300'?

Beg to differ, a good deep-reading depth sounder is a very useful
navigational aide. Can be used to determine how far offshore you are,
pick up undersea canyons which lead to harbors and anchorages,
establish a single LOP, etc.. An example: Consulting a chart reveals
there are no onshore hazards (pinnacles, reefs) outside the 100 fathom
line of a particular shore. Using the depthsounder, one can follow
the 100 fathom contour line and be assured of no nasty surprises on a
coastal passage.



Looking at the incredibly tortuous depth contours off the West of Scotland
where I sail, I would run out of fuel double-quick if I followed them, and
in a sailboat under sail, forget it! I could not care less once the depth
gets above 10 metres.


You don't need to follow countours to use depth in navigation. If
something else fails, you can take soundings at regular time
intervals, mark them on a piece of paper to the scale of your chart,
and move the paper parallel to your course until you get a match.


Rodney Myrvaagnes J36 Gjo/a


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