I don't understand what you're showing us. I was really hoping there was/is something that could be a unique combination of material and detector. Like some unusual type of material that isn't common and likely to be lying around and a detector that would only detect that type of material. Really I was imagining there are such things made specifically for this type of situation, so you can turn the sensitivity way up and wave the detector around and it can tell you what part of the yard to move toward even if it's 50' way, then as you get closer turn the sensitivity down as you get nearer to the target. Maybe it's naive on my part to think there actually is such a system already available, but I don't think there's anything wrong with wishing that there was if there truly is not. Or is that what you have presented and I just don't understand what you're showing us yet?
Thanks to all of you for your suggestions!
David
Maine, USA