Colorado State law requires these surveys prior to new construction to ensure that structures are not built over, or too close, to abandoned wells. This is due to several wells leaking in the past that were under homes, then the well exploded and destroyed the home (and residents).
www.cpr.org
All magnetometers are passive sensors that measure a combination of the earth’s field plus the induced field from any metallic target. Magnetometers can be total field or vector, which measures the magnetic field as a function of direction. The magnetic anomaly signal drops off as 1/R^3, where R is the radius between the target and sensor. The ability to detect a target is therefore a function of distance to the target, noise level, and sensitivity of the magnetometer.
I think you'll have better luck mapping the area with gravimeter (the term is "microgravimetry"). But to be detected by either technology, the gold cache should be dragon's lair worthy.
So, what kind of geophysical technique would be usefull to try to locate a threasure ( gold coins, silver coins )?
Depends on a treasure. Both magnetometry and gravimetry only work with huge caches – large enough to affect Earth's gravity or magnetic field. Both are useful in finding caves though, and if there's a cave and a cache on the same acreage, there's a good chance that it will be hidden in that cave. But if you know for a fact that someone dug a deep hole to bury their stash on otherwise undeveloped land, LIDAR mapping can be extremely helpful starting point.
Thank you very much, if we are talking about 30 cm X 30 cm X 30cm; would it be enoguth to affect gravity ? and it is in inside of a wood box ? could it be detected ? or only metal detectros ?
I'm not keeping track of the latest (and outrageously expensive) technology, but I don't think it can be seen by aerial magnetometry or gravimetry. Ground level sensors maybe, but at this point a 2-box detector will probably do just as well at a fraction of the cost. Or if you want to go "21st century", rent a ground penetrating radar – depth's gonna be very similar, but results will look super fancy.
Abouth the 2-box detector agree to probably be good one; 99thpercentile, what is your opinion like expert ?
Gravity surveys are expensive and slow. A Scintrex CG-6 micro-gravimeter is probably $120K. I would never do this to find a small near surface target. One of my former colleagues, Dwain Butler wrote a paper on detecting unexploded ordnance (UXO), It os possible, but not economical
GPR really isn’t a great approach to large area surveys for metallic targets.
I wouldn’t use hobbyist equipment for large area searches. Depending on the size of the area to search, I would use a Geonics EM61-MK2 or EM31 with a decent GPS receiver.
Oddly enough, EM61-MK2A that you recommend below is listed on many sites (including rentals) as a GPR. And I certainly meant something like it, not the likes of OKM Fusion, which falls under "exercise equipment" category.
Hello, what is your thougths about the OKM Fusion? do you have it?
I have, use and love an adjustable kettlebell from Bowflex. It's also about 142x cheaper than OKM Fusion.
