Detailed visual seabed survey at drilling site 7218/11-1

Figure6. Plannedsurveyroutefor detailedsite surveyat Darwin,August2012.
Thesurveygrid comprised33 lines,eachof which is 800m in length.Thedistancebetweenthe lines
is 25 m. The total length of the survey route (using a hypothetical straight line between the
waypointsand includingthe transit between lines) was approximately 27 200 m (26 400 m if only
linesare included). All the abovewaypointswere used,althoughthe actualROVtrack variedslightly
accordingto currentsand objects of biologicalinterest. Because currentswere reported to havea
strongeasterlydirection,the directionof the maintracklineswasrotated 90 degrees.
The ROVwas launchedon 18.08.2012at 13:53 local time (-2h for UTC),starting from the first
waypoint at 14:41. The survey was completed on 19:08.2012 at 06:24 and ROVrecovery was
completed at 06:47. Total video time was 17h 05m 06s, and total ROVdeploymenttime was the
same(videopermanentlyon).
2.4 Observation logs and event logging
2.4.1 Steps taken to address challenges
Oneof the challengesof conducting biologicalanalysesfrom non-geo-referencedvideo and/or still
photographsis the time-consumingwork of matching imagesor recorded 'events' to geographic
positions.TheROVdive log recordsthe time of eachnote, or event taken,but the positionsneedto
be matchedwith the surveyorlog.Thesurveyorlog continuouslyrecordsthe ROVtrack,but doesnot
containthe biologicalobservations.
Detailed site survey at PL531 Darwin
Akvaplan-niva AS Rapport 6051 - 1 11