Written by the TreasureGuide for the exclusive use of the Treasure Beaches Report.
I decided to discuss discrimination today.
Yesterday I decided to detect an area that is so junky it is almost impossible to metal detect. There are so many junk targets that you can't swing without hearing a lot of signals. Much of the junk is aluminum of various shapes and forms but also many other metals, including iron, copper, etc. I was using the Minelab Equinox.
I didn't think there was much h chance of finding anything good, but it was close to home, and I felt like seeing what I could do. There was a good chance that if anything good was found, it would be old. In any case, it was a good test of patience and the discrimination capabilities of the metal detector.
One thing you never know when using discrimination. As far as I know, no one has ever done experiments that accurately shows how the amount of discrimination used relates to the number of missed good targets, and I doubt they ever will. It would be difficult to do good experiments like that.
It is easy to think that the metal detector and your skill level is good enough that you aren't missing anything good, but that, in my opinion, is an illusion. You never find out what you miss. Discrimination, therefore, is usually judged by missing junk targets, and people feel that when they are not digging junk targets, they are doing well because that is what they want to avoid. They seldom think about the other side of it.
It might be possible, thought difficult, to do meaningful experiments, but I doubt anyone will ever do that because of how difficult it would be. Therefore our best information comes from detecting an area with more discrimination, and then going back over the same area with no discrimination, or considerably less, and seeing how many good targets you find. That tells, to some extent, how much you missed as the result of using discrimination, but there are still uncontrolled factors that ideally should be controlled or accounted for.
I once posted the results of a lot that was metal detected heavily before being sifted thoroughly. The results were amazing. MANY silver coins were found after several attempts at metal detecting the area. That is the best information I have on the subject, but it is only one case, and in some respects, was not typical.
One important thing that should be taken into account when deciding on how much discrimination to use is the quality of targets. Not all targets have the same value. You can consider all coins to be good targets, but it is much more significant if you are a gold coin instead of a penny, dime or quarter. The value of probable targets is a huge consideration. Missing one gold coin can be like missing a hundred thousand pennies. So it isn't a simple binary issue. Not all good targets have the same value. Far from it.
Another factor is the amount of information you get from your metal detector, and also how accurate or it is and how skillfully you use that information. We know that some good targets will give the same conductivity numbers as junk targets. That is an unfortunate fact, but there is other information you can use besides the numbers. You might be able to tell something about the shape of the target for example. Still, you might not be certain what is under your coil until you see it.
Generally speaking, the relationship between the number of detectable (not too deep) good targets to the number of junk targets in the area will affect the usefulness of discrimination. If there are very few junk targets, it is not worth using discrimination at all.
There are many situations, including many on the beach, when I advise not using discrimination. I often advise digging everything. When there is the possibility of high value targets, you don't want to miss a single one. And most beaches these days are pretty clean (though of course not all), so in those cases, you don't gain much by discriminating. If you don't know the beach well, you can do a little sampling, so you get some idea how much junk there is. No reason to discriminate at all when there is very little junk.
I can see this discussion could go on for days, but let me jump to the chart at the top of the post.
We do not know exactly what is in the ground when we start detecting. We do not know either the number of junk targets or the number of detectable good targets. I am confident, though, that, in general, as discrimination increases, so does the number of missed good targets. You may never find out if you missed good targets, and you might feel good knowing that you didn't dig any junk, but I don't want to miss good targets even if it means digging a lot of junk. That is partly a personal preference. I can tolerate digging more junk than most, I guess. But there are other factors to consider, including the probable ratio of junk to good targets and the probable value of targets. There are several ways to make those estimates.
As you turn up discrimination, it is likely in areas where there is a mixture of types of targets, that the number of missed good targets will increase along with the number of missed junk targets. The shape of the relationship between the amount of discrimination and missed good targets could be a straight-line relationship, as shown by the center line (A) above, or it could be a more complex relationship.
Line B shows a hypothetical curvilinear relationship. A little increase in discrimination is associated with would cause a greater increase in the number of missed good targets. Line C, on the other hand, shows a case where a little increase in discrimination does not result in many lost good targets until you increase discrimination to higher levels. It is important where your most desired targets might fit in. If it is a larger item that is not easily discriminated, or a target that presents a specific and well-known conductivity number so you can easily pick it out, that is important information that can affect your strategy.
There are a variety of factors that determine the relationship between the amount of discrimination used and missed good targets, but now these days, unlike the past, we do not typically have a single knob to turn discrimination up or down. Metal detectors now provide more information. On the Equinox and many other detectors, you probably get get what we call conductivity numbers. So it is no longer simply a matter of increasing or decreasing discrimination. So it becomes more a matter of making decisions on the basis of those numbers. And the important thing is how well those numbers discriminate between good and junk targets. For example, does a particular number indicate a coin or gold ring rather than an aluminum bottle cap or some other junk target. As we know, the numbers do not always perfectly discriminate. These days the additional information actually requires more operator skill. You can assume that the numbers always tell you perfectly and feel good even when you miss good targets that you'll never know about if you don't dig them up. Thankfully on beaches with few targets of any kind you don't have to worry about discrimination much.
I learned the harm using too much discrimination not too long after I began metal detecting. Back then, many metal detectors, such as Fisher 1280, provided a single knob to increase or decrease discrimination. In those days there was a level of discrimination at which you started to miss a majority of small gold rings. I've told this story before, but at first I thought men lost more gold rings than women because I was using a level of discrimination that caused me to miss many of the smaller women's gold rings. I didn't find out what I was missing until I turned off discrimination. Then I found out that women were losing gold rings in large numbers too, but I didn't find out what I was missing until I turned off discrimination. I was also learning to use strategies that made discrimination unnecessary.
With conductivity numbers it is not such a linear matter. You are not just turning discrimination up or down. Now you have to learn your numbers and what they tell you. You have to learn how skillfully use the information provided.
The type of junk that is present is an important factor. Sometimes you will get the same reading from a piece of junk as a good target. How reliably can you tell the difference between the two? Again, the value of good targets and the possible variety of good targets is important an important consideration. If there is the possibility, or likelihood, of a single extremely high value target, you don't want to miss that one target. Your estimate of the probabilities can be informed by research and sampling.
Yesterday I was detecting an area with tons of junk and very few good targets of moderate value in between. That was a different kind of situation. It was absolutely impossible to dig everything without heavy duty equipment. I was challenging, to say the least. Near impossible because every sweep resulted in several signals, many giving numbers that correspond to coins, but not being coins. That kind of situation gives a small chance of a good find, but a small chance there is. What it will give you is some good practice and better knowledge of your metal detector.
If I was actually working this site seriously and thought there would likely be a target good enough to justify the effort, there could be more effective techniques than metal detecting. Sifting would be more effective, for example. For me, at this time, it is more about curiosity and practicing in thick junk conditions.
I'll have to continue this topic some other time. It seems it could go on for days.
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| Magnified Photo of Monarch Butterfly Egg on Leaf. |
Here is a video of the newly hatched caterpillar eathing the remains of the egg. That is something you can't see with the naked eye.
And here is a link to a video I made showing the newly hatch caterpillar eating the remains of the egg. Again, something you can't see with the naked eye.
(324) Newly hatched Monarche butterfly caterpillar eating its egg. - YouTube
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| Source: nhc.noaa.gov |
There is a little system that you can see down by Texas. We'll watch that.
We are having very big tides, both high and low.
The surf is still low though - running about one or two feet all week.
Good hunting,
TreasureGuide@comcast.net