UAS Magnetometer Surveys

99thpercentile

Full Member
Nov 2, 2006
125
75
Evergreen, CO
Detector(s) used
Geonics EM61-MK2, Geophex GEM-3, GapEOD UltraTEM III, Minelabs F3, Foerster MINEX 2FD 4.500
Primary Interest:
All Treasure Hunting
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I did lots of UAS magnetometer surveys last week. We were looking for 31 well locations on a 635 acre site. We flew 15 grids with a QUSPIN, INC. Total Field Magnetometer Gen 2 (QTFMv2) with the newest prototype data logger connected to a DJI M210. We utilized Eikon Technologies QCTool software to clean up the data files and MagPick by Mikhail Tchernychev to perform the reduction to the pole (RTP) and target picking. The biggest surprise was the well in the southwest corner where I couldn't find a target signature. After lots of digging on the Colorado Oil & Gas Conservation Commission (COGCC) website and a few phone calls, we confirmed that a well was commissioned at that location but never installed. Only one well was still exposed, which can be a good check on your picking ability.
 

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99thpercentile

99thpercentile

Full Member
Nov 2, 2006
125
75
Evergreen, CO
Detector(s) used
Geonics EM61-MK2, Geophex GEM-3, GapEOD UltraTEM III, Minelabs F3, Foerster MINEX 2FD 4.500
Primary Interest:
All Treasure Hunting
  • Thread Starter
  • Thread starter
  • #3
Interesting. What is the purpose of locating these wells?
Mike
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).
 

Zakon Krzyżacki

Hero Member
May 25, 2022
842
2,540
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).

Exploding Wells ??
Fracking related ?
I guess that would be an Erin Brockovich thing.

I've never heard of a well pulling a St. Helen's.
 
OP
99thpercentile

99thpercentile

Full Member
Nov 2, 2006
125
75
Evergreen, CO
Detector(s) used
Geonics EM61-MK2, Geophex GEM-3, GapEOD UltraTEM III, Minelabs F3, Foerster MINEX 2FD 4.500
Primary Interest:
All Treasure Hunting
  • Thread Starter
  • Thread starter
  • #5
Exploding Wells ??
Fracking related ?
I guess that would be an Erin Brockovich thing.

I've never heard of a well pulling a St. Helen's.
 

GoDeep

Bronze Member
Nov 12, 2016
2,073
4,417
Detector(s) used
Whites, Garrett, Minelab
Primary Interest:
All Treasure Hunting
So that instrument detects magnetic anomalies?

What's it's range, meaning how far above the target can it be and still detect it?
 
OP
99thpercentile

99thpercentile

Full Member
Nov 2, 2006
125
75
Evergreen, CO
Detector(s) used
Geonics EM61-MK2, Geophex GEM-3, GapEOD UltraTEM III, Minelabs F3, Foerster MINEX 2FD 4.500
Primary Interest:
All Treasure Hunting
  • Thread Starter
  • Thread starter
  • #7
So that instrument detects magnetic anomalies?

What's it's range, meaning how far above the target can it be and still detect it?
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.

A good resource for approximate detection depth as a function of target type and size is Sheldon Breiner’s Application Manual for Portable Magnetometers.


For example you should be able to detect a large car at 100 ft, or a ball bearing at 8-12 inches.

The wells in the example above are ideal targets that are typically vertical pipes that can be 1000+ ft long. I fly at 100 ft and they are quite easy to find.
 

Cuco

Greenie
Jul 12, 2022
19
12
Hello 99th Pecentile,

I have a doubt about the magnetometer, i know it can detect the magnetism and the gold is a diamagnetic element, so would the gold generate an opposite valué and then be detected in the graph ? Or it is not possible ?

Thank you very much
 

pulltaboo

Jr. Member
Jul 29, 2022
49
91
North GA
I have a doubt about the magnetometer, i know it can detect the magnetism and the gold is a diamagnetic element, so would the gold generate an opposite valué and then be detected in the graph ? Or it is not possible ?
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.
 

Cuco

Greenie
Jul 12, 2022
19
12
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 )?
 

pulltaboo

Jr. Member
Jul 29, 2022
49
91
North GA
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.
 

Cuco

Greenie
Jul 12, 2022
19
12
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 ?
 

pulltaboo

Jr. Member
Jul 29, 2022
49
91
North GA
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.
 

Cuco

Greenie
Jul 12, 2022
19
12
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 ?
 
OP
99thpercentile

99thpercentile

Full Member
Nov 2, 2006
125
75
Evergreen, CO
Detector(s) used
Geonics EM61-MK2, Geophex GEM-3, GapEOD UltraTEM III, Minelabs F3, Foerster MINEX 2FD 4.500
Primary Interest:
All Treasure Hunting
  • Thread Starter
  • Thread starter
  • #15
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 ?
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
 
OP
99thpercentile

99thpercentile

Full Member
Nov 2, 2006
125
75
Evergreen, CO
Detector(s) used
Geonics EM61-MK2, Geophex GEM-3, GapEOD UltraTEM III, Minelabs F3, Foerster MINEX 2FD 4.500
Primary Interest:
All Treasure Hunting
  • Thread Starter
  • Thread starter
  • #16
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.
GPR really isn’t a great approach to large area surveys for metallic targets.
 
OP
99thpercentile

99thpercentile

Full Member
Nov 2, 2006
125
75
Evergreen, CO
Detector(s) used
Geonics EM61-MK2, Geophex GEM-3, GapEOD UltraTEM III, Minelabs F3, Foerster MINEX 2FD 4.500
Primary Interest:
All Treasure Hunting
  • Thread Starter
  • Thread starter
  • #17
Abouth the 2-box detector agree to probably be good one; 99thpercentile, what is your opinion like expert ?
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.
 

pulltaboo

Jr. Member
Jul 29, 2022
49
91
North GA
GPR really isn’t a great approach to large area surveys for metallic targets.
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.
 

Cuco

Greenie
Jul 12, 2022
19
12
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?
 

pulltaboo

Jr. Member
Jul 29, 2022
49
91
North GA
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.

On a serious note though, there's at most 2 reasons to prefer a handheld GPR – portability and handling on rough terrain. That's it, IMO. Me and my shoulder will take a wheeled GPR for any other occasion. And if you don't do it for a living, there's no reason to even own one, there are plenty of rentals available.
 

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