A check on a singlebeam echo sounder: a flat bar or plate is lowered on marked lines to set depths below the transducer, and the sounder reading is compared at each step. The comparison yields the index error and an average sound speed for the shallow water column. It serves on singlebeam systems and as a sanity check of multibeam nadir depths, especially before contract surveys.
Bar check at 2, 4 and 6 metres all within 2 centimetres, the sounder's good.
Also heard as
- bar check calibration
- plate check
Related terms
Singlebeam echo sounder
An echo sounder that measures one depth directly beneath the vessel on each ping, using a single vertical beam.
Lead line
A marked line with a lead weight on the end, used to measure depth by hand and to check echo sounders.
Static draft
The vertical distance from the waterline down to the transducer face while the vessel is at rest.
SVP
Sound velocity profile: how the speed of sound changes with depth through the water, measured to correct sonar depths.