Tuesday, March 15, 2016

3/15/16 Report - Finding Shipwrecks Using Satellite Images. Target ID Issues.

Written by the Treasureguide for the exclusive use of treasurebeachesreport.BlogSpot.com.

NASA Satellite Photo Showing Plumes From Two Shipwrecks.
Researchers have found that shipwrecks near the coast can leave sediment plumes at the sea’s surface that help reveal their location. Using data from the NASA/USGS Landsat 8 satellite, researchers have detected plumes extending as far as 4 kilometers (about 2.5 miles) downstream from shallow shipwreck sites. This discovery demonstrates for the first time how Landsat and Landsat-like satellites may be used to locate the watery graves of coastal shipwrecks....

While airborne lidar (which uses light pulses to measure distance) can be used to detect shipwrecks close to shore and multibeam echosounders and other sound-based methods can be used anywhere deep enough for a survey vessel to sail, the former method requires clear water and cost prohibits both methods from being used to conduct exhaustive coastal surveys.
A new study published in the Journal of Archaeological Science by authors Matthias Baeye and Michael Fettweis, from the Royal Belgian Institute of Natural Sciences; Rory Quinn from Ulster University in Northern Ireland; and Samuel Deleu from Flemish Hydrography, Agency for Maritime and Coastal Services, aims to change things. The authors have found a way to use freely available Landsat satellite data to detect shipwrecks in sediment-laden coastal waters...

The two plumes coming from the shipwrecks marked by the two red dots are not easy to see in the above photo.  You might be able to see them more clearly if you use the link to go to the original article.

Here is the link for the entire article.


They say that ignorance is bliss.  It might be bliss and a lot of other things, but it is still ignorance.  I never make mistakes in my posts - at least not until I go back and check them, use spell checker, or post them. Then I find tons of mistakes that up until that point I didn't know I made.

The same thing is true in metal detecting.  You never know what you miss.  You never know for sure until you dig.  You might think you know.  You might be highly accurate, maybe even 99.9 % accurate, and that might be good enough for you, but for me, I get surprised from time to time, and the surprises are very valuable.  The surprises might be few, but it is the surprises that I learn from.  And it is the surprises often turn out to be rare artifacts or especially valuable items like Rolex watches.

I'm not trying to convince anyone.  I know that there are people who can not be convinced.  I learned long ago, that you can seldom change someone else's mind.  I'm just telling how I see it.

I might be the only one that has to actually dig a target and see it to be absolutely sure what it is. Everybody else might be 100% accurate with their target signal identification.  They might be absolutely certain that the target they just passed up was a pull tab or penny.  And they might never make a mistake.

I'm just not that good.  Every time I dig up a Rolex or some unusual artifact, I'm surprised.   Some of my most valued finds were complete surprises.

For a few years I wasn't digging iron and I wasn't digging big stuff.  I was focused primarily on coins and jewelry.  As a result, it took me a long time to find shipwreck spikes.  That was a conspicuous absence from my list of finds.  Now I don't like to miss shipwreck spikes so I change my decision strategies.  Now I usually dig things like that when I am in an area where they might be found.

That word "usually" is an important word.  I don't always dig those types of things - just when I am in the right places and when it fit my goals.

To optimize success it is important to take in to account a variety of factors.  I'd be an even bigger fool than I am to hunt the same way everywhere no matter what the situation or what I am trying to accomplish.

A lot of my strategy is to hunt areas where the types of things that I am targeting are concentrated. These days I seldom hunt where there are lots of the kinds of items that I want to skip.  So when I am successful in doing that, discriminating those items does not save a lot of time because they are simply not there in great numbers.  And when I run into a lot of them, I am in the wrong kind of area, and I move.  As I've explained before, junk provides information too.

I  can't get into that in any more detail now.
The other day when I was talking about some of the most popular detectors as indicated by the Kellyco People's Choice Awards.  I gave some of my positions on target ID.  One of the things I mentioned was that target ID is not perfect.  Just a few minutes ago I went to YouTube and the first video I looked at illustrated what I was saying.  The title of the video is Target Issues With the CTX 3030.  The guy, who seemed to be very thoughtful and competent, was running into a lot of twist off caps which gave him something like a 1242 reading. so he was bypassing them as would be natural. He didn't know what he missed on the first pass when he passed up items that gave that type of reading.  He decided to go back and check some that he passed on the first pass.  He ended up being surprised and thought maybe he should go back and check some of the other signals that he passed on.

Take a look a the video.  I highly recommend going through the entire thing.  It illustrates many points that I have mentioned in the past.

Here is the link.


If you want to skip over targets, and everybody does to one extent or another, (there are definitely times to skip things) there is nothing wrong with that, but I want you to be aware of what could be happening.

I never have to tell people to use discrimination.  People will naturally do that.  Judging from my experience they are more likely to discriminate too much rather than too little.  And I will never convince anyone to dig more even though that is a lesson I've learned for myself.  Maybe I'm the only one that occasionally makes a big mistake when I don't dig.

Digging also has other benefits that I like.  I like removing junk from places that I hunt a lot so there are fewer junk signals when I return.  I don't like getting any kind of signal from the same pull tab day after day so I remove a lot of them.  It doesn't really take long to make a place you hunt frequently much less junky.  You can do it bit by bit.


I'm expecting to receive a report on a home site that was thoroughly sifted that will show how much is really there and how much is usually missed.  I can't wait to see the final report.


On the Treasure Coast expect a couple of days of one-foot surf.  The wind will be mostly from the west.

Happy hunting,