Aqua Survey's EM Sled used by Mel Fishers

[rgecy]

I didn't know if you guys had seen this. I had kept hearing about the new Technology the Fishers were using on the Atocha Site. Apparently they hired a company called Aqua Survey. The EM Sled is pretty interesting.

http://www.aquasurvey.com

Check out some of the videos:

http://www.youtube.com/watch?v=eXN4idWDGHI

http://www.youtube.com/watch?v=id-A_EMtGCM

http://www.youtube.com/watch?v=wPnrDEwjtDM

http://www.youtube.com/watch?v=aQZCO1v71xI

[CanadianTrout]

Wow, great stuff. Thanks for the post RGecy!

[itmaiden]

The link goes "nowhere". Want to check that URL again ?

itmaiden

I didn't know if you guys had seen this. I had kept hearing about the new Technology the Fishers were using on the Atocha Site. Apparently they hired a company called Aqua Survey. The EM Sled is pretty interesting.

http://wwww.aquasurvey.com

[lurediver]

Thanks for sharing.

[rgecy]

The link works now! Too many W's!

Robert

[nyc37]

Cool technology that sled, a pulse metal detector on mega-steroids!


My personal belief is that Atocha stern castle has been salvaged in contemporary times, although no records...
Just too precious to give it up.

Will keep watching.

[rgecy]

I think its scattered all to heck from the second hurricane. The stern castle broke away and was tossed all over the place. I just don't see that there is any way its stayed all together.

Robert

[signumops]

Excellent! Now, about the GPS fixin's on that diver propelled sled...? Would be great if you could get some sort of radio wave effects working in the water (at an affordable level). Implying precision positioning would mean the GPS receiver was fixed at the detector's head, or, perpendicular to it at the water's surface. What says ya? A pinger to fixed datum would work too, but how would you collect the signal from the detector without wire? The absolute BEST thing would be a position tracking display so the diver could see where he's been previously while he is using the thing. Macro-cosmic version of magging, so to speak.

[Trond]

Very interesting, thanks for sharing.

[rgecy]

I would say they are using triangulation with a pinger system to get accurate gps position. Pretty much the only accurate way to do it underwater.

Robert

[SFLOcenEng]

Excellent! Now, about the GPS fixin's on that diver propelled sled...? Would be great if you could get some sort of radio wave effects working in the water (at an affordable level). Implying precision positioning would mean the GPS receiver was fixed at the detector's head, or, perpendicular to it at the water's surface. What says ya? A pinger to fixed datum would work too, but how would you collect the signal from the detector without wire? The absolute BEST thing would be a position tracking display so the diver could see where he's been previously while he is using the thing. Macro-cosmic version of magging, so to speak.

From Wikipedia

USBL (Ultra-short baseline) is a method of underwater acoustic positioning. A complete USBL system consists of a transceiver, which is mounted on a pole under a ship, and a transponder/responder on the seafloor, a towfish, or on a ROV. A computer, or "topside unit", is used to calculate a position from the ranges and bearings measured by the transceiver.

An acoustic pulse is transmitted by the transceiver and detected by the subsea transponder, which replies with its own acoustic pulse. This return pulse is detected by the shipboard transceiver. The time from the transmission of the initial acoustic pulse until the reply is detected is measured by the USBL system and is converted into a range.

To calculate a subsea position, the USBL calculates both a range and an angle from the transceiver to the subsea beacon. Angles are measured by the transceiver, which contains an array of transducers. The transceiver head normally contains three or more transducers separated by a baseline of 10 cm or less. A method called “phase-differencing” within this transducer array is used to calculate the angle to the subsea transponder.

USBLs have also begun to find use in "inverted" (iUSBL) configurations, with the transceiver mounted on an autonomous underwater vehicle, and the transponder on the target. In this case, the "topside" processing happens inside the vehicle to allow it to locate the transponder for applications such as automatic docking and target tracking.

[Voldbjerg]

I would say they are using triangulation with a pinger system to get accurate gps position. Pretty much the only accurate way to do it underwater.

Robert

Actually using gyros and accelerometers would be more precise. All you would need is the starting position then it is possible to calculate the movement. Sort of like in a Wii stick or iPhone - you might need better and more sensors though.

[aquanut]

Voldberg, That, along with the computer is basically what is used in a ships internal navigation system (SINS).
Aquanut

[SFLOcenEng]

Voldberg, That, along with the computer is basically what is used in a ships internal navigation system (SINS).
Aquanut

I believe it's inertial navigation systems not internal.

[FISHEYE]

The best way to do underwater GPS is with this device.

http://www.cadivingnews.com/gear/810...Underwater-GPS

Mount it on the MD sled,put a camera on the GPS and you have real time GPS.They could even put a depth gauge on it and have a camera on that too.

Or

If you really have the $$$

The Submersible GPS-Iridium Antenna.

http://www.soundocean.com/products/in-water-gps

This technology is out there if you have the cash,but theres always the poor mans way of doing it.

[aquanut]

You're right SFLOcenEng. It's been 40 years and too many Captain and Cokes!!!
Aquanut

[crzhors]

As for affordable Underwater GPS, Check YouTube under "underwater gps", my friend Mark Thome has been using a Magellan Sportrak inside a clear pelican type case,for many years and I used the same unit with great results. Just let the case float to the surface,catch a heading,reel it back down.record the heading and move on to your next spot. He used to have a Yahoo group called "Diver GPS". Very usable for us mere mortals.