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CM2 Sidescan Sonar User Manual
4. Planning the Survey
4. PLANNING THE SURVEY
Survey Plan
Every survey or search needs to be planned in advance. Survey planning and post-processing are topics
that are wider than can be covered here. Most sonar acquisition software packages, including MaxView,
include the facility to plan survey lines for guiding the helmsman.
Line Spacing
The frequency and range settings should be defined for the type of task being planned, whether it is a search
for a wreck or lost anchor, or a post-dredge clearance check, for example.
The image quality is reduced in the region below the towfish because the image when received is
compressed and also the steep angle results in poorer shadow information. The quality is also reduced at
the extremity of the range primarily because of beam spreading. Survey lines should therefore be spaced
with sufficient overlap (e.g. 75m when working with 100m range setting) to ensure complete coverage.
Overlap is also necessary to compensate for course deviations.
Line Direction
It is normally preferable to run survey lines in the same direction as any current. Where currents are very
strong the lines may need to be run in only one direction, against the stream, as running with the stream
would give too high a speed over the ground thereby reducing the number of pings on any target.
Typical Small Survey; Area Sweep inside a Harbour
Version 3.6 (2008)
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