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#40
12-05-2010, 06:35 PM
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Quote:
People report that for finding buried metal, the afternoon and early evening is best. I have read no reports about finding disturbed soil. But I have experience from using Infrared thermometers, and cameras. Some examples: 1. Digital thermometer: When using an ifrared thermometer, the surface temperature changes for the same soil when you move the thermometer from shadow to sunshine at close distance. You will see sometimes up to 50 degrees difference, but usually 10-20 degrees cooler in shadows of the same soil. When the same soil changes from wet to dry, you will also see changes maybe the same as caused by shadows or less. From a larger distance, maybe 5-10 meters small shadows are not seen, only the larger shadows. But the temperature of the ground can be seen to change when the ground is changed. For example, ground with a grass lawn shows a different temperature than the same ground with no grass or plants on it. And when the ground changes from soil to concrete, or to asphalt, or other kind of soil, then the temperature usually shows a change. These changes are easiest to see when there is good sunlight on the surface (day time). 2. Thermal imaging camera: A thermal imaging camera is very good at finding very small differences in temperature and showing them in an image. I have not used these cameras for locating treasures, but I have taken them outside on occasions to see what I they would show. You will find a thermal imaging camera shows images of the area where you point it. You will also see images of things that do not exist... In a parking lot, you may see images of cold shadows where a car was parked recently. You may see images of footprints if you have a good quality thermal camera that is set for the temperature of a surface where somebody walked. You may see underground pipe locations if conditions are good. You will definitely see wet spots on the ground and on other surfaces. You may even see damp or wet objects behind walls. You may see a lot of other things I did not think to look for at the time. Since you are looking for disturbed soil or for caves, a thermal imaging camera may be able to find temperature differences you are looking for. If the disturbed soil has the same consistency as the soil around it, then it may be difficult to see as a temperature difference. Especially if the soil has weathered to blend with the surrounding soil. But if someone dug a hole recently and covered it back with the same soil, it will not have the same density of the soil around it. This means it will not absorb or retain water the same as the surrounding soil, and the evaporation of water will not be the same unless the density/compaction is the same. In this condition, I would expect a thermal imaging camera to show a different temperature in the location of the re-filled hole when the temperature of the soil is changing, maybe in the late afternoon. Or maybe in full sunlight if the wind is blowing hard, and not any plants on the surface. If this same hole was dug and refilled more than 100 years ago, then maybe enough time has passed to allow natural geophysical forces to cause the fill dirt to compact and become like the surrounding soil. Or maybe not. I never checked this. If the disturbed soil has settled long enough to become the same as the surrounding non-disturbed soil, then you will not see a temperature difference caused by different density. In any case, it is expensive to rent or to buy a thermal imaging camera. Make sure you are using one that is sensitive to very slight temperature differences in the temperature range you expect to see at the soil. Best wishes, J_P 
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