3-21
3.13 Towfish Deployment
The 4125 Towfish can be towed at speeds of up to 4.8 knots while still meeting NOAA and IHO-44S
specifications of 3 pings on a 1-meter cubed target at 100 meters. Shown in FIGURE 3-15 is a 4125 Towfish
being deployed.
CAUTION! The deployment instructions below are only meant as a
general guide. Due to varying conditions, exact deployment methods will
change and it is up to the end user to modify their deployment procedure
to match the conditions they are working under.
CAUTION! When lowering the towfish in an area where the bottom
topography is not known, be careful not to strike the bottom or a
submerged object. Otherwise, damage to the towfish may occur. In
addition, at all times during the survey, carefully monitor towfish altitude,
as failure to do so may result in the towfish hitting the bottom or
becoming snagged.
CAUTION! Do not tow the towfish too close to the survey vessel. Towing
in this manner can cause the towfish to be pulled in against the hull of
the ship due to the low pressure of the propeller wash and the effect of
the water flowing by the hull. In addition, sonar reflections from the hull
may be evident in the records.
CAUTION! Do not tow the towfish with the nose angled up or down.
Doing so can degrade the sonar imagery. Verify that the towfish is as level
as possible when towing it. Adjust the position of the tow arm so the
towfish is as level as possible (+5 is optimal).
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