Thursday, March 06, 2008


Sonar scanning of HMAS Sydney site begins


Perth Now
By Braden Quartermaine
March 06, 2008

SONAR scanning of the HMAS Sydney search area off the WA coast has begun - despite initial fears about the difficult seabed terrain.

Shipwreck hunter David Mearns initially feared the difficult seabed encountered could sabotage the mission.

But after a few "uneasy'' hours, Mr Mearns said the seabed flattened out and his dream of solving our greatest wartime mystery is now continuing in earnest.

The 24-hour a day search that will continue for up to two months or until the Sydney is discovered, with Mr Mearns predicting "many twists and turns to come''.

"As our sonar was tracking through the initial section of our first trackline I started to get very concerned that luck wasn't going to be on our side,'' Mr Mearns said.

"The seabed geology wasn't that awful, but it certainly wasn't going to be easy to detect a shipwreck amongst all the geological formations that cluttered our screens.

"The Geosounder's watch officers were also finding it difficult maintaining the perfectly straight trackline we require at the slow speeds of 2.5 knots. The combination of the two difficulties, amongst a number of other technical issues, made the first few hours searching very uneasy.

"As the sea is ever changing, however, so was our fortunes and a couple of hours later the seabed started to get very flat and featureless -- ideal terrain for shipwreck hunting -- and the Geosounder began crabbing down the line at an angle that maintained good steerage as well as speed.

"It always takes some time to iron out the kinks and for a search to take on a pattern and rythm of efficiency and this is what first tracklines are for. We can only hope that our good fortune continues although experience tells me that there are many twists and turns to come.

"The most anxious time for any search is the first sonar trackline through the search area. This is when you learn whether the area you are searching consists of either rough geological terrain or a flat smooth seabed.

"You also learn for the first time whether the weather and sea conditions will allow you to tow the sonar in the direction and speed your desire without difficulty. Complications due to rough geology and/or uncooperative weather and sea conditions can make all the difference to whether a search ends successfully, or in failure.''


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