Detailed visual seabed survey at drilling site 7218/11-1
Detailed visual seabed survey at drilling site 7218/11-1
Detailed visual seabed survey at drilling site 7218/11-1
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Figure6. Planned<strong>survey</strong>routefor detailed<strong>site</strong> <strong>survey</strong><strong>at</strong> Darwin,August2012.<br />
The<strong>survey</strong>grid comprised33 lines,eachof which is 800m in length.Thedistancebetweenthe lines<br />
is 25 m. The total length of the <strong>survey</strong> route (using a hypothetical straight line between the<br />
waypointsand includingthe transit between lines) was approxim<strong>at</strong>ely 27 200 m (26 400 m if only<br />
linesare included). All the abovewaypointswere used,althoughthe actualROVtrack variedslightly<br />
accordingto currentsand objects of biologicalinterest. Because currentswere reported to havea<br />
strongeasterlydirection,the directionof the maintracklineswasrot<strong>at</strong>ed 90 degrees.<br />
The ROVwas launchedon 18.08.2012<strong>at</strong> 13:53 local time (-2h for UTC),starting from the first<br />
waypoint <strong>at</strong> 14:41. The <strong>survey</strong> was completed on 19:08.2012 <strong>at</strong> 06:24 and ROVrecovery was<br />
completed <strong>at</strong> 06:47. Total video time was 17h 05m 06s, and total ROVdeploymenttime was the<br />
same(videopermanentlyon).<br />
2.4 Observ<strong>at</strong>ion logs and event logging<br />
2.4.1 Steps taken to address challenges<br />
Oneof the challengesof conducting biologicalanalysesfrom non-geo-referencedvideo and/or still<br />
photographsis the time-consumingwork of m<strong>at</strong>ching imagesor recorded 'events' to geographic<br />
positions.TheROVdive log recordsthe time of eachnote, or event taken,but the positionsneedto<br />
be m<strong>at</strong>chedwith the <strong>survey</strong>orlog.The<strong>survey</strong>orlog continuouslyrecordsthe ROVtrack,but doesnot<br />
containthe biologicalobserv<strong>at</strong>ions.<br />
<strong>Detailed</strong> <strong>site</strong> <strong>survey</strong> <strong>at</strong> PL531 Darwin<br />
Akvaplan-niva AS Rapport 6051 - 1 <strong>11</strong>