Thermal imaging method to detect subsurface objects
First Claim
1. A method for remotely sensing subsurface objects and structures, comprising:
- a. selecting one or more input parameters indicative of a host site environment of a host at a first location and a subsurface object site environment of a subsurface object that is beneath a surface at a second location, wherein said host site environment is naturally heated to a depth below said subsurface object;
b. using said one or more input parameters in a heat-transfer calculation, calculating at least two sensing times, either twice daily for a daily cycle for objects no deeper than three feet, or twice yearly for a yearly cycle for objects deeper than one foot, wherein a first sensing time of said at least two sensing times is when an object-site temperature is maximum and a host-site temperature is distinguishably less, and wherein a second sensing time of said at least two sensing times is when an object-site temperature is minimum and a host-site temperature is distinguishably more;
such that the temperature when said object-site temperature is maximum minus the temperature when said object-site temperature is minimum, referred to herein as the object site temperature spread, is distinguishably more than a host-site temperature spread;
c. sensing, at said first sensing time, when said object site temperature is maximum, one or more wavelengths from each of two different thermal infrared (IR) wavebands, wherein one of said IR wavebands comprises a range from about 3 microns to about 5 microns and the other of said IR wavebands comprises a range from about 8 microns to about 12 microns, and recording a spatial sequence of dual-band IR images;
d. sensing, at said second sensing time, when said object site temperature is minimum, said object site with said IR wavebands, and recording another spatial sequence of dual-band IR images;
e. calculating (using an image processing code) signal ratios and differences to form temperature, emissivity-ratio and corrected-temperature maps;
f. co-registering said corrected-temperature maps to form a first sensing time object-site corrected maximum temperature map and a second sensing time object-site corrected minimum temperature map and subtracting said second sensing time object-site corrected minimum temperature map from said first sensing time object-site corrected maximum temperature map, to form co-registered object-site temperature-spread maps with said corrected-temperature maps;
g. correcting said co-registered temperature maps and said co-registered temperature-spread maps by removing and replacing apparent thermal patterns with spectral differences in either of said thermal IR wavebands;
h. removing host-site irregularities and foreign-object thermal clutter from said temperature-spread maps;
i. determining object location, size, shape and orientation from said temperature maps;
j. determining object, thickness, volume, and depth information from said temperature-spread maps; and
k. providing a 3D display of said object-site temperature maps and said object-site temperature spread maps.
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Abstract
A thermal imaging method to detect heat flows from naturally-heated subsurface objects. The method uniquely combines precise, emissivity-corrected temperature maps, thermal inertia maps, temperature simulations, and automatic target recognition to display clear, clutter-free, three-dimensional images of contained hollow objects or structures, at depths to 20 times their diameter. Temperature scans are corrected using two different infrared bands. Co-registered object-site temperature scans image daily and seasonal temperature-spread differences, which vary inversely as the object'"'"'s and surrounding host material'"'"'s thermal inertias. Thermal inertia (resistance to temperature change) is the square root of the product (kρC), for thermal conductivity, k, density, ρ and heat capacity, C.
30 Citations
25 Claims
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1. A method for remotely sensing subsurface objects and structures, comprising:
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a. selecting one or more input parameters indicative of a host site environment of a host at a first location and a subsurface object site environment of a subsurface object that is beneath a surface at a second location, wherein said host site environment is naturally heated to a depth below said subsurface object; b. using said one or more input parameters in a heat-transfer calculation, calculating at least two sensing times, either twice daily for a daily cycle for objects no deeper than three feet, or twice yearly for a yearly cycle for objects deeper than one foot, wherein a first sensing time of said at least two sensing times is when an object-site temperature is maximum and a host-site temperature is distinguishably less, and wherein a second sensing time of said at least two sensing times is when an object-site temperature is minimum and a host-site temperature is distinguishably more;
such that the temperature when said object-site temperature is maximum minus the temperature when said object-site temperature is minimum, referred to herein as the object site temperature spread, is distinguishably more than a host-site temperature spread;c. sensing, at said first sensing time, when said object site temperature is maximum, one or more wavelengths from each of two different thermal infrared (IR) wavebands, wherein one of said IR wavebands comprises a range from about 3 microns to about 5 microns and the other of said IR wavebands comprises a range from about 8 microns to about 12 microns, and recording a spatial sequence of dual-band IR images; d. sensing, at said second sensing time, when said object site temperature is minimum, said object site with said IR wavebands, and recording another spatial sequence of dual-band IR images; e. calculating (using an image processing code) signal ratios and differences to form temperature, emissivity-ratio and corrected-temperature maps; f. co-registering said corrected-temperature maps to form a first sensing time object-site corrected maximum temperature map and a second sensing time object-site corrected minimum temperature map and subtracting said second sensing time object-site corrected minimum temperature map from said first sensing time object-site corrected maximum temperature map, to form co-registered object-site temperature-spread maps with said corrected-temperature maps; g. correcting said co-registered temperature maps and said co-registered temperature-spread maps by removing and replacing apparent thermal patterns with spectral differences in either of said thermal IR wavebands; h. removing host-site irregularities and foreign-object thermal clutter from said temperature-spread maps; i. determining object location, size, shape and orientation from said temperature maps; j. determining object, thickness, volume, and depth information from said temperature-spread maps; and k. providing a 3D display of said object-site temperature maps and said object-site temperature spread maps. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25)
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20. A thermal imaging method to detect subsurface objects or air gaps, comprising:
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using an energy budget equation to calculate a first imaging time and a second imaging time; imaging two different infrared (IR) wavelength bands a at said first imaging time from a first location and a second location to obtain a first temperature map; imaging said two different IR wavelength bands a at said second imaging time from said first location and said second location to obtain a second temperature map; combining said first temperature map and said second temperature map to obtain a first temperature spread at said first location and a second temperature spread at said second location; and comparing said first temperature spread with said second temperature spread to determine whether an object or structure is located beneath said first location or said second location.
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Specification