Questions on Boat Towed Magnetometers

[GreginAlaska]

All,
Greg here. I am new to this website and apologize if I am making this post in the wrong forum. I am new to this and am looking for advice. I have done a search on this website and was not able to find answers to my questions, so am posting here as the most logical thread. I am trying to locate a large iron anchor in approximately 150' of salt water. I am told that a towed magnetometer is the correct tool to locate items such as this. I have a large boat and winch system capable of deploying such a device, but am totally ignorant about all aspects of this activity. Also, a quick google search revealed equipment from JW Fishers that is fairly expensive. I am not opposed to the prices, but sure need to know what I am doing first. I have the following questions if you would be so good to answer;
1 - Are there any expositions or conferences I could attend where I could look at towed magnetometer equipment and discuss it's operation with knowledgeable people and compare different manufacturers?
2 - Does anyone have a recommendation of a preferred brand or style of towed magnetometer for locating ferrous metal?
3 - Is there charting software available that takes GPS information as an input, to correctly locate anomalies identified by the towed array system?
Thanks for any answers and information you are willing to share.
Greg

 

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[Darren in NC]

If you're serious about it, find someone who can run lanes with a Geometrics Cesium G-882 mag. It is the industry standard, and is your best shot at finding it. They can be rented for a fair price, but you need someone who knows what they're doing with logistics and software.

 

[GreginAlaska]

If you're serious about it, find someone who can run lanes with a Geometrics Cesium G-882 mag. It is the industry standard, and is your best shot at finding it. They can be rented for a fair price, but you need someone who knows what they're doing with logistics and software.

Thanks Darren, I appreciate the recommendation for the magnetometers. I looked it up on line, and it looks like an excellent piece of equipment with a great detection range. I will look into rentals.

Would you have any recommendations on industry expo's or conferences where I could compare equipment and rental companies to see what else is out there and who provides rentals, etc.? I have been to the Seattle Fish expo, and just about every commercial fishing equipment and boat manufacturer puts in an appearance. It is a huge conference and is very easy to compare equipment from different manufacturers, etc. Is there anything comparable in this industry? I would imagine that there have to be many companies out there performing similar operations, like locating pipelines for oil companies, lost anchors, etc. I there any annual gathering for a conference somewhere? Just asking, like I said, I am new to this an I appreciate your feedback.
Thanks,
Greg

 

[agflit]

Greg-

I agree with Darren wholeheartedly... and would reiterate that the most important aspect of the entire situation revolves around the Mag operator... a well versed, dedicated expert in the specific machine used is paramount to success.
A few questions... how specific is your search area? What depth is the bottom? hat is the bottom composition? Do you have known coordinates as to the anchor site, or are you looking in a wider ranging area? If it is a large area, mowing the lawn will take time and can be rather expensive.... you can expect to spend well over 2k a day JUST for the operator, not including the equipment lease, boat costs, misc expenses such as travel and mobilzation, etc etc etc...it adds up VERY fast.

I'd do a thorough cost / benefit analysis prior to leasing a mag... make sure that it's worth going after. Don't forget, finding it is one thing..than you have the expense of the actual recovery operations after the Survey phase... not trying to dissuade you, just do your homework, line up your ducks, and go in with your facts at hand and your eyes wide open..

Let us know if we can be of any further help..

Ag

 

[Mackaydon]

Do you need a permit to salvage in that area?
Have you determined the area is not restricted for any reason that would prohibit your activity (example: Marine Sanctuary)?
Don.....

 

[GreginAlaska]

Do you need a permit to salvage in that area?
Have you determined the area is not restricted for any reason that would prohibit your activity (example: Marine Sanctuary)?
Don.....

AG/Don
Thank you for the feedback. Answers to your questions as follows;
1 - The anchor was lost some time ago and is a British Kedge Anchor. I am told that a typical Kedge Anchor of this time period would weight ~1,500 lbs and were constructed of iron.
2 - Bottom composition is mud/sand. There are fairly uniform water depths in the area; no large pinnacles or reefs. Some small rock piles.
3 - There is a respectable tidal current in the area. This will likely complicate search via towed magnetometer.
4 - Water depth is between 100'-150' of water.
5 - This an area with high vessel activity, and has had this activity for a considerable time period. I expect there is probably more than 1 anchor in the area, along with the typical debris/junk from years of vessel traffic. This will probably complicate detection with lots of false positives. The water current and time since it was lost, along with the bottom composition, may have resulted in the anchor being buried in the bottom sediment/mud/sand.
6 - The coordinates of the lost anchor were recorded on charts by the vessel at the time, but this was in a time before modern charts or navigational instruments. The old chart does overlay with known land features of modern charts, but there is some mismatch/inaccuracy. Even if the original location on the original chart is correct, there could still be 2-3 miles of error in knowing the location, depending on how the 2 charts are overlaid. I am aware that this is a huge area. I expect I will have to "mow the lawn" for a significant time in order to find the anchor, so yes I expect it to take a while. There is some historical significance to the anchor that would make it worth recovering.
7 - I have not yet investigated permits. The chart indicates that it is located in state waters (within 3 miles of shore here), but depending on how inaccurate the charts are, it may lie further offshore in federal waters. My plan was to locate it, then seek a permit for recovery. Basically, I don't want to advertise that I am looking for it, until I find it. Is this a bad plan?
Thanks for all of the help, I appreciate your input.
Cheers,
Greg

 

[FISHEYE]

You could rent the Geometrics Cesium G-882 mag from geometrics with a option to buy it.You will pay a lot less for a mag this way.