Roll
Roll turns up in 2 fields: fiber optics, hydrography. Here is what it means to the people in each one.
Roll in fiber optics
To swap the two fibers of a duplex pair so transmit and receive line up with the far end.
When a duplex link shows light leaving both transceivers but neither receives, the pair is crossed the wrong way, and the quick fix is to reverse the two connectors at one end. Many LC duplex clips can be opened and flipped for exactly this. Crews say roll it, flip it or swap the pair, and the change should be made at a jumper, never by re-terminating the permanent cable.
"Still no link on 24, roll the pair at the patch panel and tell me what the switch says."
Roll in hydrography
Rotation of a vessel about its fore-and-aft axis, measured to correct the angle of every sonar beam.
Side-to-side rotation, measured by the motion sensor and applied to every beam so depths land in the right place. Because outer beams are long, a small roll error makes a large vertical error: a 0.1 degree bias moves a beam at 60 degrees in 20 m of water about 6 cm up or down. Roll bias between motion sensor and transducer is found in the patch test from reciprocal lines over flat seabed.
"Roll's off by 0.08, the swath tilts opposite ways on the reciprocal lines over the flat."