Geophysical Instrumentation Questions & Suggestions

[99thpercentile]

I am a geophysicst who works mainly with detecting landmines and unexploded ordanance (UXO) for the US Army Corps of Engineers. I have been reading through the forums on geophysics to get a feel for what people here use in terms of hardware and software. Would people post back to this message with a list of hardware and software that they use. Please include the equipment name, manufacturers name and website. I am asking this since most people on this forum are amatuer treasure hunters and not geophysicsts. I would like to help explain the fundamental concepts of how some of these instruments work so that you can make better choices in selecting the correct instruments. To do this I need a list of what you are currently using or investigating. Thanks.

Ryan E. North
Research Geophysicst
BS Engineering Physics
MS Geophysical Engineering
PhD Geophysics (in progress)

[HiiiQ]

EM-83 geo-western.com
white's TM-808
The more important question is -what are you using?

[99thpercentile]

I've never used analog sensors like most people on here use except for a Minelabs F3 ($3K) or F1A4 or a Foerster MINEX 2FD 4.500 ($3K). Geophysics almost exclusively use digital sensors that record the sensor output as well as the sensor position. We occasionally do a dead reckoning survey which involves laying out a grid, typically 50 meters by 50 meters. Then the end of each line is marked with a plastic flags and then evey 10 meters along each line a flag is placed in the ground. Geophysical sensors have a button on them to mark the data each time the button is pushed. After the data collection is completed the data is downloaded to a computer and the marks are all put at their correct location. Then a map of the sensor responses is created and we look for anomalies. At a more advanced level we attempt model the data to take the measured results and determine the distribution of physical properties that created the response, this is called geophysical inversion which most people would take a class in until they are a MS or PhD student.

Dead recking surveys are very rare now in geophysics. I typically use a survey grade GPS unit and log my position and sensor response simultaneously. Here is a brief list of the equipment that I use for a land based survey. Now before anyone has a heart attack at the approximate prices I have included, realize that most companies don't buy these sensors outright, they just rent them by the job. For many trasure hunting and metal detecting hobbiests, a sub $1000 metal detector will be all they ever need.

Metal Detectors
Geonics EM61-MK1($20K), EM61-MK2($26K), EM63($35K)
Geophex GEM3($20K)

Soil Conductivity Sensors
Geonics EM31($15K), EM34($18K), EM38B($13K)
Geophex GEM-2($20K), GEM-2H ($35K)

Magnetometers
Geometrics G-856($25K), G-858($30K)

Ground Penetrating Radar
GSSI SIR-3000 system with all antennas from 12.5 MHz to 1.5 GHz ($80K)
Sensors & Software PulseEKKO Pro with all antennas from 20 MHz to 1.5 GHz

Soil Magnetic Susceptibility Sensors
ZH Instruments SM-30 ($1500)
Bartington Instruments MS-2(B,C,D,F) ($9K)

Handheld field computers
Juniper Systems Allegro CX ($3K), Archer ($1500)
TDS Systems Recon ($1600), Ranger ($3K)

GPS
Trimble 5700 RTK system ($45K), DSM-232($5K), AgGPS132($4K)

Satellite Correction Services
OmniStar VBS ($800/yr), XP($1600/yr), HP($2500/yr)

[Black Cloud]

Ryan, I am using an CM-031, made by GF Instruments in the Czech Republic, very similar to the EM-31, except mine has a HP 200 palmtop that records the data as I do the survey. Therefore I can see whats going on at all times. I use the RockWorks 99 program and am very satisfied with both. I also set up a 50 meter grid when possible, and the Garmin 12 GPS (my 3rd one) is all I'll ever need to record locations, etc. I have an older IBM ThinkPad laptop that I take to the field with me to convert to imagery on the spot. I also have two - box detectors and handhelds for pinpointing purposes. Appreciate your help and advice in these areas - most geophysists charge an arm and a leg for knowledge that took them half a lifetime to acquire.

[99thpercentile]

I have seen the CM-031, but never used it. All of the instruments that I use allow for realtime viewing of the current profile and most of them can also show a map of where you have collected data so far. I am very interested in improving the entire data collection procedure to allow some real-time analysis. For data analysis I used a laptop in the field and a range of software.

General mapping and gridding software
Golden Software: Surfer, Grapher, Voxler
Geosoft: Oasis Montaj
Geometrics: MagLog, MagMap, MagPick

[tagasilay]

Hi Ryian,

I have the regular twobox tf-900 by discovery, and the minelab sov., these have recovered uxo from the last war, napalm canisters, live jap grenades, ammo, and even a 160lb aireal. We also have a ramac x3m but i only have the 250shielded mgz antenna, for me the best option for general purpose treasure hunting. we use the professional firmware and groundvision program. Manufacturer is malageoscience based on sweeden. It has 3 pre sets for deep, medium and shallow but you can manually set the system to suit the enviroment you are in. you can set the velocity (in usltrasecounds), sampling frequency, zero level etc. it also has a gridproject program for 2.5d imaging (X,Ygridding) and real time basic image filtering. I use the cart triggering method since it saves power and is more precise in measurement and auto stacking to save memory. Of course nothing comapared to what you have. I bet your minelab can detect 1/4 of a pin in the ground at 4-5 inch depth, my surfmaster pulse could do it when it was still working.HH

Happy thanks giving
to all Americans
Jose

ps i have also seen their higher frequency antenas used in imaging rebars in cement, should do well when looking for plastic mines.

[GRZ]

I stumbled onto this site while searching for info on building a 12 inch airlift ,if anyone has any idea. I want to fit an IMS 22'floating dredge to pass sand and gravel with 10% gravel 4-6" .
but I have a drilling rig and want to use some of the high tech gadgetry that y'all have been talking about including shalow seismic to find coal deposits in shales and sandstones , and do you think GPR would have a shot at this application?
I would be using the electronics in conjunctin with bore holes
just fewer holes.
thanks
Greg