Geo examiner – part 2 – the device, impressions

cholomanaba

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Aug 22, 2011
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After the bad taste of the purchase and the release from customs, I sat down, stared at the whole device for a while and asked myself…. now what?

At the WEB page you can see pictures of the device and the way it is operated by a technician, but in reality the buyer finds himself surrounded by about 30 different pieces of the device (32 if we count the extra 15-hour dry-cell battery and its charger). All this parts are equally important and must be remembered so as to avoid forgetting any of them at the field. It is at this time where one has to reassure himself about the decision made. One have to focus on his objective, because it is easy, very easy to think that you may have made the wrong choice of detector, and get scared (it happened to me)… or in your case, if you make it wrong.

I knew, beforehand, that operating this type of device was not going to be an easy task because it required time, patience and some help. The device can be operated by a single person, but it takes some time to make the measurements alone, minimum two people and the ideal three. You will understand what I mean. Although its complexity, I chose this device because it has some advantages that I will describe later.

Anyway, despite all those parts, not all of them will be used at the same time. Let me explain: at the WEB page, it is said the device has three methods of scanning, I would say it has four. The first one is a system with 4 rods that you stick in the soil, and you pull them and stick them again for each square or fraction of the area you are scanning. The second one is a set of 22 rods stuck in rows or a column 10mt long, each time you make a new column you only move one row of 11 rods, usually to the right. The third method is a gradiometer, which can be used similar to the OKM devices (holding at a steady height and facing the same direction all the time – let’s say north). And the fourth method is a metal detector same as a regular one, but with the feature of charting the area you are checking.

With the first, the third and the fourth methods you have the choice of scanning without charting, it means that at the computer screen you can find a number similar to those of a regular metal detector. This number indicates resistivity. When you chart, then the computer takes this number and places it in a matrix or square to show the graph - like placing the numbers inside a spreadsheet. The device does not make a sound at all in any of the methods.

The second method is more complex, because it requires two or three people to move the rows of rods before completing the chart. As I said before, a single person can realize the scan, but it will take more time because he has to pull and stick again each row of 11 rods with its corresponding wire. If it is done between two or more people, then the measurements become easier. This method seems to me it is more adequate because it can reach deeper and more precisely.

The first and second methods are called geophysics, which means that the device, after making a ground calibration for the type of soil, realizes a scan of each square and memorizes that number. That number indicates the resistivity of the soil. If there is a metallic object, there will be less resistance and more conductivity. But at the same time it compares this number with four other around (north, south, east, west) and produces an average. The first number is the resistivity at that square, and the second one, (the average) indicates the normal value or the average of the whole area. Likewise, this number is compared with the starting measurement or ground calibration, to make sure there are no mistakes in the reading. I understood this by reading the WEB page and before buying the detector, also during its operation. This scanning method looked more reliable to me than the one made by OKM, because the OKM devices require you to state the type of soil in which you are operating, in order to determine the existence of a metallic object and its depth. If the operator fails and state a different type of soil, the device may ignore the target, take it as mineralization, and/or place it at a wrong depth. The advantage of the OKM devices is their simplicity of operation and a low number of parts.

The third method, the gradiometer, I still don’t master it, because it requires the operator not to wear any or big metallic objects. This may include metallic zippers of pants or jackets, metallic things in shoes or boots, coins, keyrings, rings, etc. I mention MAY because I am not still sure how it affects the performance of the gradiometer, but when you operate it, you better keep it away even from the computer itself. At the moment I am only using this method as a backup for target re-check and I am not charting anything, just looking at the numbers.

The fourth method, the metal detector, as a matter of fact I don’t care much about it, it came with the device, but I think I will use it for charting when scanning inside old houses, walls and fences, just to know if there are nails (dots), electric wires (lines) or any hidden cache (squares, rectangles or circles).

The first few times that I went to test the device I took the cases with me, but they are very heavy and bulky. Anyhow, it is risky to draw atention of peasants watching a group of foreigners walking in their lands with black, shiny suitcases (see images at www.imagelocators.com ). So I replaced the cases with a large and strong backpack, that way I can carry the whole device. Inside a backpack it is easier to carry all that weight and leave my hands free to carry the shovels or to get hold of anything. The heaviest parts are the rods (22 stainless steel rods 1/8” in diameter and 50cm long) and the extra battery (a dry-cell battery 12V 7.5Ah, similar to those used for UPS). I still don’t test the backpack in far away places where we have to walk for hours or climb mountains… I will have to ask for help of the strongest of the group or find a mule.

Besides the detector, the user should carry measure tape, preferable 50mt long, string and wood sticks. These will be useful to demarcate the area and divide it in squares. That way any of the four methods of scanning can be used, the measurements will be more even and the objects can be easily found. In case of hard ground, a wood or rubber hammer can be used so you don’t damage the rods.

I personally prefer to demarcate areas of 10mt x 10mt (100mt2).

continues….
 
very interesting. curious how it would proform in rocky soils. how small of a target can this device find?
also curious about the TITAN finder
 
There is another good machine for electric resistivity called OhmMagic that create 2d images like this
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