A performance requirement stated as the smallest cubic object the whole survey system must reliably find, for example 1 m cubes for Special Order or 2 m cubes for Order 1a. It depends on beam footprint, sounding density, ping rate, vessel speed and processing, so a setup that passes at 15 m may fail at 40 m. Many specifications also demand several soundings on a feature before it counts as detected.
At this speed we're only getting two pings on a metre cube, slow down to five knots for feature detection.
Detection fails first in the outer beams and at the deep end of the area, so speed limits are set for the worst case on each line.
Also heard as
- object detection
Related terms
Special Order
A survey order for harbours and channels where under-keel clearance is critical, with full coverage and 1 m feature detection.
Order 1a
A survey order for coastal waters and fairways where features matter but under-keel clearance is less critical.
Contact
A target picked out of side-scan or multibeam data that may be an object worth investigating.
Least depth
The shallowest depth over a wreck, rock or other feature, which is the value that gets charted.
Coverage
The portion of the seabed actually measured or imaged by a survey, expressed as a percentage of the area.