99thpercentile
Full Member
- Nov 2, 2006
- 161
- 125
- Detector(s) used
- Geonics EM61-MK2, Geophex GEM-3, GapEOD UltraTEM III, Minelabs F3, Foerster MINEX 2FD 4.500
- Primary Interest:
- All Treasure Hunting
I have no idea what type of "geophysical" instruments OKM manufacturers. I contacted them once to ask what geophysical principle(s) their instruments operated under (electromagnetic induction, magnetometry, or ground penetrating radar) but didn't get an answer. Any real manufacturer of geophysical instruments will have extensive documentation of the specific method at each instrument operates under as well as lots of details about the specific details of the instrument. For example a manufacturer of a time domain electromagnetic induction metal detector will list the type of transmitter pulse, the shape of the pulse and the duty cycle. They will list the number of time gates, the width of the time gates and the time of the beginning or center of the time gate. They will list the number of transmit cycles per second as well as any analog or digital stacking (averaging). Then they will give you detailed information about the data file structure, all real geophysical instruments save the data.
Any company attempting to sell you an instrument that is more complex than a handheld metal detector that doesn't give all of the above information is most likely hiding something. A simple test is to see if the instrument is being used by commercial geophysical companies, ask for a list of companies using the instrument. If a vendor doesn't readily supply a list of current commercial users with contact information, ask yourself why.
I'm very confused about Frankn's comments, if he did work on government projects using airborne sensor platforms it definitely wasn't in a science or engineering capacity. He doesn't seem to know the difference between the global positioning system (GPS) and ground penetrating radar (GPR). GPS is how you know where your data was collected, I typically use a $50K Trimble 5700 or R8 RTK GPS system to position my data to <1cm accuracy for geophysical surveys. GPR is a great tool in specific situations, but I have never seen it used successfully to locate a 20 ft deep tunnel on the border (my group has the lead for this issue for DoD). Airborne GPR systems are typically synthetic aperture radar (SAR) systems and they can be very useful, but don't typically have very much depth penetration (<2m). I have some spectacular GPR results from some sites and very poor results from other sites. GPR is just one tool in the geophysicists toolbox, the selection of the correct tool is based on: site geology, type of target, size of target, depth of target, and the contrast of one or more physical properties between the target and the host medium. One tool never fits all sites or situations.
Any company attempting to sell you an instrument that is more complex than a handheld metal detector that doesn't give all of the above information is most likely hiding something. A simple test is to see if the instrument is being used by commercial geophysical companies, ask for a list of companies using the instrument. If a vendor doesn't readily supply a list of current commercial users with contact information, ask yourself why.
I'm very confused about Frankn's comments, if he did work on government projects using airborne sensor platforms it definitely wasn't in a science or engineering capacity. He doesn't seem to know the difference between the global positioning system (GPS) and ground penetrating radar (GPR). GPS is how you know where your data was collected, I typically use a $50K Trimble 5700 or R8 RTK GPS system to position my data to <1cm accuracy for geophysical surveys. GPR is a great tool in specific situations, but I have never seen it used successfully to locate a 20 ft deep tunnel on the border (my group has the lead for this issue for DoD). Airborne GPR systems are typically synthetic aperture radar (SAR) systems and they can be very useful, but don't typically have very much depth penetration (<2m). I have some spectacular GPR results from some sites and very poor results from other sites. GPR is just one tool in the geophysicists toolbox, the selection of the correct tool is based on: site geology, type of target, size of target, depth of target, and the contrast of one or more physical properties between the target and the host medium. One tool never fits all sites or situations.