초록 ▼

Most mines and underground facilities employ standardized construction techniques and materials. Such also cannot avoid having some above ground openings to receive utilities, fresh air, supplies, etc. Those or other surface openings are also universally used to discharge ground water, wastes, and o

Most mines and underground facilities employ standardized construction techniques and materials. Such also cannot avoid having some above ground openings to receive utilities, fresh air, supplies, etc. Those or other surface openings are also universally used to discharge ground water, wastes, and other materials. Typical underground facilities have abundant electrical wiring and power demands, both of which can be detected at the surface. Levees with leakage pathways also form electrical conductors. When properly illuminated with remotely generated electromagnetic (EM) radiation, many of these features will "glow" or reradiate the radio energy in an electronic signature unique to the underground facility. Synchronized EM-gradiometer transponders are situated nearby on the ground surface to collect and analyze the "glow". Alternative transmitting devices further includes ways to generate the illumination, and computers for characterizing the return signatures.

대표청구항 ▼

Most mines and underground facilities employ standardized construction techniques and materials. Such also cannot avoid having some above ground openings to receive utilities, fresh air, supplies, etc. Those or other surface openings are also universally used to discharge ground water, wastes, and o

Most mines and underground facilities employ standardized construction techniques and materials. Such also cannot avoid having some above ground openings to receive utilities, fresh air, supplies, etc. Those or other surface openings are also universally used to discharge ground water, wastes, and other materials. Typical underground facilities have abundant electrical wiring and power demands, both of which can be detected at the surface. Levees with leakage pathways also form electrical conductors. When properly illuminated with remotely generated electromagnetic (EM) radiation, many of these features will "glow" or reradiate the radio energy in an electronic signature unique to the underground facility. Synchronized EM-gradiometer transponders are situated nearby on the ground surface to collect and analyze the "glow". Alternative transmitting devices further includes ways to generate the illumination, and computers for characterizing the return signatures. ange in phase difference of the first and second sinusoidal field components between the second and third points, the determination of a predetermined phase relationship tracing the conductor from the second point to the third point and the determination of a change in said phase relationship indicating a different conductor is being traced from said second point; and, wherein the frequencies F1and F2are phase-locked and related by N×F1=M×F2,where N and M are non-adjacent integers greater than 1, one of which is odd and one of which is even, having no common factors. 2. A method according to claim 1, wherein the first and second points are the same. 3. A method according to claim 1, wherein the second and third points are remote from the first point. 4. A method according to claim 1, wherein the step of determining includes multiplying the first sinusoidal field component by M and the second sinusoidal field component by N. 5. An apparatus for tracing a conductor, comprising: generation means (10) for applying an alternating signal to a first point on the conductor (12), the alternating signal having first and second continuously present sinusoidal components with frequencies F1and F2respectively; detection means for detecting at a second point and at a third point the field produced by the alternating signal on the conductor, the field having first and second continuously present sinusoidal field components with frequencies corresponding to the frequencies of the first and second sinusoidal components of the alternating signal; and determination means for determining any change in phase difference of the first and second sinusoidal field components between the second and third points, the determination of a predetermined phase relationship tracing the conductor from the second point to the third point and the determination of a change in said phase relationship indicating a different conductor is being traced from said second point; characterised in that: the frequencies F1and F2are phase-locked and related by N×F1=M×F2, where N and M are non-adjacent integers greater than 1, one of which is odd and one of which is even, having no common factors. 6. An apparatus according to claim 5, wherein the generation means is arranged to generate the first and second sinusoidal components of the alternating signal. 7. An apparatus according to claim 5, wherein the detection means is arranged to multiply the first sinusoidal field component by M and the second sinusoidal field component by N.