Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
Updates
Gallery
Video Clips
Expedition Updates

19/07/01 - Day 18

Combing the search box

Rob White reports

As the sidescan sonar 'Ocean Explorer' travels deep into the ocean, it has a very precise duty to carry out - derived from the equally deep research carried out over the last 6 years by our Search Director David Mearns.


David monitors the sonar

David's researches have taken him on a long journey into British, American and German archives, to find the best information he can to work out where we should search for the wrecks of both 'Hood' and 'Bismarck'. He uses every piece of data he can to tell him where he should go - especially any positions reported by nearby ships (though of course in those days they didn't have 'global positioning by satellite' to help them.)

Using that information - which includes details from ship's logs showing how they approached the site of the sinking - David creates a "search box".

The search box (click to enlarge)

Then parallel courses are plotted to give 'lines' for the sonar to travel up and down, sweeping the seabed below with electronic pulses that get a return signal from large objects - especially metal ones. Late last night we began our third line of the 10 David has fixed.

Each 'line' is 60 kilometres long, and the whole box is 600 square miles in area. At the end of each line 'Northern Horizon' must turn in a long arc, taking up to 5 hours, to allow the six thousand (or more) metres of cable paid out to the sonar to turn too.

Gently does it. That cable is literally our lifeline.





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