Operating Guidelines - C-Max CM2 User Manual

CM2 Sidescan Sonar User Manual

6. Operating Guidelines

6. OPERATING GUIDELINES
Do not allow the towfish to hit the bottom – be very careful when turning
Fly the towfish on as straight a course as possible, to prevent distortion and
smearing of the image
Fly the towfish lower (but safely clear of the bottom) to give best image
shadows, e.g. 5m altitude; fly it higher to give longest effective range, e.g.
10m altitude or more, except in shallow water
Use the higher frequency for best image resolution, and for small targets; use
the lower frequency for longest effective range, and for big targets
Use 10deg transducer depression in normal circumstances; use 20deg
depression if the bottom image is being obscured by reflections from the sea
surface
Higher tow speeds are ok for LF (100kHz) operations, e.g. up to 6 knots
Use lower tow speed for HF (325kHz) operations, e.g. 4 knots
Use lowest tow speed for EF (780kHz) short-range operations, e.g. 3 knots
Low speed gives more "pings" on each target and gives greater towfish depth
for any particular tow cable length
High speed makes it easier to keep the towfish on a straight course
Overlap survey tracks to give best target detection probability; overlap by at
least 2x altitude (approximate rule), ideally 100%
Orthogonal survey tracks (e.g. E-W then N-S) may give more information on
target shape
During the survey always watch the image in NORMAL geometry to check
that the bottom-tracking (automatic altitude measurement) is locked on to the
bottom echo
If the bottom-tracking loses lock use altimeter forcing buttons (up-down) to
restore the correct indicated altitude
Check the incoming nav data and don't forget to RECORD the sonar data!
Version 3.6 (2008)
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