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22/07/01 - Day 21

Keeping in position

Rob White reports

The ROV is now travelling over the wreck site - searching out the best pictures of the wreck of HMS 'Hood'.


George Holmes at work

But it would have a job getting any of them if it weren't for the technical wizardry of 'Global Positioning by Satellite'. 'Northern Horizon's G.P.S. signal comes down into the ship through an equipment array above the bridge - fixing where she is so that once we have a site to work on we can stay on it.

All the time of course wind and wave are doing their best to push us OFF that position. That's where George Holmes, Dynamic Positioning Operator, and his 'D.P.' kit come in.

The ship has side and bow thrusters, controlled by a computer programmed with the position we need to be in. If we move from that, the D.P. computer instructs the thrusters to put her back on the spot.


The radio mask on board Northern Horizon

But getting the D.P. to work properly is still down to human experience. For a start, judging the best direction to point the ship for the ROV to work well is down to a seaman's judgment.

And even G.P.S. has to be fine-tuned. That's done by cross-checking where the satellite SAYS something is against where it ACTUALLY is, on a good old-fashioned chart. Then our navigator, Chris Jones of Thales Geosolutions, will measure the difference between the two positions, adjust the fix we want to use accordingly.

"One Hundred and Eighty!" - you're on the bullseye and ready to get to work.





Full Listing
26/07/01 -
Finally - a service of remembrance


25/07/01
The Hood Photo Appeal

25/07/01 -
More big discoveries


23/07/01 -
She's found!


22/07/01 -
Keeping in position


21/07/01 -
Tracking the ocean floor


20/07/01 -
Sonar finds "promising target"


19/07/01 -
Combing the search box


18/07/01 -
Transfers and goodbyes


17/07/01 -
Meet the search team


16/07/01 -
Meet the survey team


15/07/01 -
Meet the experts


14/07/01 -
Meet the film crew


13/07/01 -
Farewell to the Bismarck


12/07/01 -
A service of remembrance


11/07/01 -
More filming from the deep


10/07/01 -
The Bismarck plaque is laid


09/07/01 -
The Bismarck is found!


07/07/01 -
Staying on track


06/07/01 -
The sonar is finally launched


05/07/01 -
More frustration for the team


04/07/01 -
Rough weather halts progress


03/07/01 -
Expedition to film the Bismarck


03/07/01 -
Holding a steady course


02/07/01 -
Northern Horizon leaves Cork


28/06/01 -
David Mearns in Webchat


27/06/01 -
ITN's Rob White reports from the ship