DocumentCode :
3405377
Title :
Discrimination of buried plastic and metal objects in subsurface soil
Author :
Chin, D.C. ; Srinivasan, R. ; Ball, Robert E.
Author_Institution :
Appl. Phys. Lab., Johns Hopkins Univ., Laurel, MD, USA
Volume :
1
fYear :
1998
fDate :
6-10 Jul 1998
Firstpage :
505
Abstract :
The electrical conductivity object locator (ECOL) uses electric conductivity maps to distinguish buried foreign objects from the regular soil in the subsurface. Assuming that foreign objects and the regular soil have different electrical conductivities, when an electrical current is induced into the subsurface, the difference in conductance causes an electrical field distortion. Theoretically, one can measure the outside field distortion to solve the conductivity profile. Because the problem is highly nonlinear and has noisy field conditions, mapping the conductivity profile is an interesting and challenging task. In addition, the high contrasts in conductivity values among metallic and nonmetallic objects and soil and the high correlation within the model parameters add to the level of difficulty. The high contrast causes the computational instability in the inversion; the high correlation is due to locating the small objects. The ECOL technology utilizes several techniques to overcome the difficulties and locate the mine-like small objects. ECOL applies a low-amplitude (100-μA to 500-μA) electric alternating current, single or multiple frequency. The impressed AC current generates AC potentials and magnetic fields throughout the site; these are measured at the surface and the boundary of the site. Also, ECOL establishes a finite element model to compute the surface and boundary values from the amount of current, physical structure, and assumed or previous estimated conductivity profile of the subsurface. ECOL estimates the conductivity profile of the subsurface and the characters of the buried object by minimizing the sum of the square of the differences between the measured and the computed values. The minimization is based on a gradient approximation technique, namely, simultaneous perturbation stochastic approximation
Keywords :
Galerkin method; computerised tomography; electric impedance imaging; finite element analysis; geophysical techniques; geophysics computing; inverse problems; object detection; perturbation techniques; 100 to 500 muA; boundary values; buried foreign objects; buried objects discrimination; computational instability; conductance difference; conductivity tomography; electric conductivity maps; electrical conductivity object locator; electrical field distortion; electrical impedance tomography; finite element model; gradient approximation technique; inversion; metal objects; mine detection; minimization; noisy field conditions; nonlinear problem; plastic objects; simultaneous perturbation stochastic approximation; subsurface soil; surface values; AC generators; Conductivity measurement; Current measurement; Distortion measurement; Finite element methods; Frequency; Magnetic field measurement; Nonlinear distortion; Plastics; Soil measurements;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Geoscience and Remote Sensing Symposium Proceedings, 1998. IGARSS '98. 1998 IEEE International
Conference_Location :
Seattle, WA
Print_ISBN :
0-7803-4403-0
Type :
conf
DOI :
10.1109/IGARSS.1998.702954
Filename :
702954
Link To Document :
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