A digital set of survey lines loaded into the acquisition software and helm display before the boat leaves the dock. Spacing comes from the expected swath width at the shoalest depth on each line, minus the overlap the specification demands; orientation usually follows the depth contours so swath width stays steady along each line. A good plan also lays out crosslines, run-in distance and room to turn.
Line plan's built for 12 metres, but it shoals to 6 at the north end, so expect infills there.
Lines run parallel to the contours keep swath width constant; lines run up and down the slope make the swath breathe and leave ragged coverage.
Also heard as
- survey lines
- line file
Related terms
Mainscheme lines
The primary set of parallel survey lines that delivers the required depth coverage over a survey area.
Crosslines
Survey lines run across the mainscheme lines so the two data sets can be compared as an independent check.
Overlap
The share of each swath that is also covered by the neighbouring line, planned in to guard against gaps.
Swath
The strip of seabed measured or imaged across the track on one line of a multibeam or side-scan survey.
Run-in
The stretch before a survey line where the boat settles on course and speed before logging starts.