Track spacing (sounding survey)

Track spacing is the distance between adjacent survey lines run by a sounding vessel, the parameter that with the swath width sets how much of the seabed a hydrographic survey actually measures. Older editions of IHO S-44 specified a recommended maximum line spacing for each survey order, tightening it for the more demanding orders so a single-beam survey caught features between the lines. S-44 Edition 6, in force from 2020, replaced line spacing with a bathymetric-coverage requirement: Special Order, used where under-keel clearance is critical, now requires full 100 percent seafloor coverage with a multibeam or side-scan system. The track spacing in practice is then driven by the swath width and the overlap needed to guarantee that coverage.