Magnetometer plans

[bell47]

Hey guys, I need plans for a good magnetometer to locate a 1000 GT steel vessel in about 200-300 feet of water. Does anyone rent these things? Maybe its cheaper to rent. Thanks

 

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[garryk]

You should be using a side scan sonar, not a mag for this kind of search.

 

[Darren in NC]

Garry, why not a mag? Just curious about your take on it.

Bell47, either is expensive to buy, but rent can cost you $250+/day (no operator). If you're confident of the general location and only need it for a few days, I'd say rent one. I wouldn't build a homemade one before talking to Dinkydick on this forum.

 

[garryk]

A mag is more intensive and the max detection range for a 1000t ship is about 250 meters (500 meter swath). If the mag does not have a pressure sensor for depth or acoustic altimeter for sensor height above seafloor, knowing where it is in the water column is speculation. Processing the data takes software and the skills to use the software to end up with a good product. Also once a mag anomaly is found of the size you expect you have a whole nother step of classifying visually by camera on ROV or diver if it is the right target. Just plain inefficient. For this size ship you can with a modern 100 kHz like a Klein 3000 and detect at ranges of 400 to 500 meters per side (800 to 1000 meter swath) at a towspeed of 7 to 8 knots. Mags usually do not like being towed this fast. Do the math on coverage rate and you can see the advantage. But the real advantage is classification, once a target is located on the long search range, you can now make a pass on a shorter range for a high resolution image that can be used to measure exactly the target as well as image what it is.

 

[rgecy]

I would have to agree for this particular case. A wreck like this would be easy to spot with SSS. With a mag, you would have to follow up with either divers, ROV or a SSS to verify like Garry said.

Robert

 

[allen_idaho]

Unless this very large ship has somehow gotten buried on the sea floor (you never know), I don't think a mag is the way to go.

 

[bell47]

Thanks guys we're looking into side scan now. still looking for advice on either ss sonar or mag.