Additional lines placed midway between the original lines, halving the spacing. Splits come from singlebeam practice, where a shoal sounding between two lines demanded closer lines to pin down the true least depth and extent. The word carries over to multibeam and side-scan work when a feature needs denser data, and crews talk about splitting a line or running splits around a suspicious rise.
Got a 4.1 on line 22 that the neighbours don't show, run splits either side and put the multibeam over the top.
Also heard as
- split lines
- half-spacing lines
Related terms
Development
Extra survey work over a feature or shoal to pin down its least depth, shape and extent.
Line plan
The set of pre-planned survey lines, with spacing and orientation, that a vessel follows to achieve the required coverage.
Singlebeam echo sounder
An echo sounder that measures one depth directly beneath the vessel on each ping, using a single vertical beam.
Least depth
The shallowest depth over a wreck, rock or other feature, which is the value that gets charted.