Searching as effectively as possible

[the Swede]

I was just wondering what the metal-detecting population out there is doing to maximize the search for whatever one is hunting for?

For some time ago, I watched a short video on YouTube where two guys was searching a lake with one detector each; but the search seamed rather haphazard to me. They had no markers or anything of the like and just randomly searched here and everywhere.

But surely there must be a better way to effectively search with a metal-detector.

Have anyone experience from using rods, lines, etc as guiding-posts?



the Swede

 

[MikeDahms]

Haphazard may be one way to describe water hunting. You want to do the best you can where you are detecting, go slow learn your machine. I worked ocean beaches only so my answer is colored with that experience. Each day there are at least two tides which move sand and lost items around. So what I am attempting to say is even though you worked an area yesterday you can still find more in the same place. If I were to be working at a lake I think I would line up on an object or establish a depth to work and work parallel to the shore line. If I were working a lake and I found a lot of old trash I would be very excited, work slowly and go over the same area many times. You will get a lot better at using your machine no matter what brand it is. Lastly I will say don't worry about it, just go hunt. Hopefully this will help you. Best to you, Mike.

 

[ziphius]

Haphazard searching isn't as bad as you think. I do wildlife surveys for a living and this involves sampling along lines or transects, randomly placed in the study area. Recently, I got curious about the same question you asked and decided to do a computer simulation of a random search for a single metal object in a 100 ft. by 100 ft. field (10,000 square feet). The simulation involved a 12 inch coil, with the assumption that it could effectively search 1 square foot every three seconds. Target depth was negligible (shallow). If you searched with 100% efficiency, you would search each square foot only once and it would take you 8.3 hours, on average, to find the single object. With a random search (each square can be sampled multiple times), it would take you 9.5 hours, on average. That is only a 14% increase over perfect systematic sampling. - Jim

 

[bdahunter]

Haphazard searching isn't as bad as you think. I do wildlife surveys for a living and this involves sampling along lines or transects, randomly placed in the study area. Recently, I got curious about the same question you asked and decided to do a computer simulation of a random search for a single metal object in a 100 ft. by 100 ft. field (10,000 square feet). The simulation involved a 12 inch coil, with the assumption that it could effectively search 1 square foot every three seconds. Target depth was negligible (shallow). If you searched with 100% efficiency, you would search each square foot only once and it would take you 8.3 hours, on average, to find the single object. With a random search (each square can be sampled multiple times), it would take you 9.5 hours, on average. That is only a 14% increase over perfect systematic sampling. - Jim

Now if you random sampled but with a bias towards higher probability areas, say places like the mine and the lane; what would the chances of finding the target sooner be like? Factor in multiple targets with prime areas having much greater target density than low probability areas (like the tops of sand banks) and multipliers for experience and suddenly gridding doesn't seem like the way to go unless you're in an area with high target density. At that point you grid the heck out of it.

 

[ziphius]

bdahunter is exactly right. Throw in local knowledge of swimmer density at that particular beach, combine with careful and methodical gridding, and you will be deadly.

 

[the Swede]

Metal-detecting just turned mathematical...

 

[bdahunter]

Not really Swede. I think that detecting is part science and part artform. The first thing I do when I hit the beach is assess the conditions and the prime areas, often I find a vantage point to overlook the beach so I can get a whole picture view. I start my hunt by doing a quick pass to locate the coin line but from there I hunt by a combination of statistical probability and gut hunch. Sometimes the logical mind wins and sometimes the intuitive mind wins, the important part is that I have a good hunt either way.
Sometimes no matter what I do, I lose but those are the breaks. You can't win'em all but if you can win most of them then it's all good.
Kewl,

BDA

 

[grumpyolman]

I do use a method of a pattern search when using SCUBA or hookah in a lake. It involves scoping out the area and making an educated guess where the majority of the finds might be. As soon as I find an area of promise, I lay down a 25' braided line with a dive weight on each end of the line. I search from the center of the line out, one arm's width, till I get to the end and then I turn around and come back the other direction. After the first pass, I pick up the weight and take one step to the left and drop the weight. I then swim to the other end and pick up the other end of the line with the weight on it and take one step to my right and drop the weight to the bottom. I search as I did the first time only I am one step farther out than I was on the first pass. I try to do a little overlap so I don't miss anything.
When I make some nice finds doing a random search, I make a note of where and how deep I was and then come back at a later date and do the rough grid search. If you were wading you could do the same thing only have a light float that would stay almost directly above the weights for a reference point. You, in a lot of situations, could see the white line on the bottom and use it as your guide. Hope this helps. Regards...Jim