Originally Posted by J_Player
Hi Aurificus,
The IR thermometers do not measure temperature directly. They measure IR emissions, which are converted to temperatures electronically. Thus, the instrument I used is measuring the IR emitted from whatever surface it is pointed at, within a 10 degree cone from the tip of the sensor. The point is, that the temperature varies over any stretch of landscape which has enough texture to cast a shadow. This surface temperature variation can be as much as 30 degrees Fahrenheit, or even more depending on the sun, air temperature, and wind conditions. This condition exists on nearly all ground that has shadows and that has variations in the soil moisture content. Because this condition exists, then according to your dissertation, the detector "receiver" would require "retuning" whenever you found this change more than a few degrees. (In the location where I conducted the test, this means retuning must be done at least every 8 inches for the undisturbed sand, and every foot or so in the sand that was smoothed to remove the shadows.
But what is confusing is that you are focusing on a changing thermal gradient, using IR to detect it:
To the best of my knowledge, a thermal gradient is a gradient in temperature, is it not? You say the "changing thermal gradient" suits the idea of an IR detection device, natural fit. I am wondering if you are talking about measuring the gradient in temperature or something else. Depending on the wavelength of the IR, you may be illuminating the target area with something more similar to light, or more similar to heat. If you are really talking about a thermal gradient, then I would think it is important to choose a wavelength closer to the heat radiation end of the spectrum. But if not, then I would think it is still meaningful to at least specify what transmitted frequency is responding to the presence of a buried target.
But putting aside the exact frequency of the IR LED, your theory is that the buried metal anomaly anomaly can be detected because it received heat from the sun which was transferred by conduction through the soil. According to your dissertation, the thermal energy can easily be converted to other forms of energy: "Heat is only one form of Energy and interchangable with any other energy so detection of other changing energy is quite possible." the heat supplied by the sun is converted to a different form of energy. And this transformed energy will forma an anomaly at the treasure location, which will absorb a different amount of the IR pulsed at the soil above the buried metal.
If this is correct, then let's look back at what I measured on the ground in the way of temperature (IR emissions actually, which follow closely with the temperature). There was a 30 degree Fahrenheit temperature swing in the undisturbed soil, due to shadows, and an 11 degree swing due to moisture variations below the surface. The question that comes to mind is how will these large natural variations in soil surface temperature allow a buried metal object to receive an un-skewed amount of thermal radiation from the sun to allow the pulsed IR LED to detect the converted energy within the equivalent of a few hundredths of a degree? This seems impossible, especially when the shaded areas change as the sun moves across the sky, and moves the cool spots away from the buried metal, or toward it.
The questions that keep coming to mind are: what energy are you talking about (as in what frequency is the thermal gradient from the sun transformed into that is detected by a pulsed IR LED at the treasure location?)
And, how can you spot such a small anomaly when the source energy supplied has anomalies at and around the treasure site that are hundreds of time larger?
I believe Esteban said he found targets using infrared up to 30 meters. Am I correct Esteban?
Perhaps Esteban can shed some light on the reason to do your sampling between the hours of 10 am and 2 pm. This would help greatly to explain what phenomenon is being detected.
Best wishes,
J_P
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