A Navy ship searching for the bodies of Ben Smart and Olivia Hope has found many objects - but searchers are not revealing any details.
The captain of HMNZS Moa, Lieutenant-Commander, Tony Grubb, said much of the plot just outside Tory Channel had been covered by the ship's sonar search and some 200 "contacts" had been made.
This was around the number searchers would have expected.
A contact was an object that was foreign to the environment, he said.
"As you can imagine, what we are looking for is small, not an aeroplane or something of that magnitude. This is much more difficult, it will take a lot more analysis work."
Data from Moa's search will be taken to Auckland on an optical disc where the contacts would be reviewed in a processing suite where they can be enhanced.
Police would get a report in about six weeks, detailing how many contacts might be worth investigating.
"It's then up to police as to whether they want to pursue it further," said Commander Grubb.
Moa's brief was clear.
"We had an area we were requested to search, we made some contribution to refining the research area and we were to find what we could and send a report."
The ship is searching a patch of Cook Strait off Raukawa Head, south of Perano Head, outside the harbour limits.
It was mostly sand with only one small piece deeper than 120m, too deep for the equipment to search, Commander Grubb said.
As the sea bottom and its objects are viewed in real time, an operator reading from a sonar image display marks contacts and makes notes about them.
If a contact is considered of particular interest, the sonar is taken close to the object to get a picture from a different angle and a scan is done to determine its composition.
Objects can be measured accurately in three dimensions.
Commander Grubb said Moa's side scan sonar, computer processor and sonar image display were designed to locate mine-like objects, typically 50-75 sq. cm.
- NZPA
200 hits in sea hunt for Ben and Olivia
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