Microwave reflection survey technique for determining depth and orientation of buried objects

Claim 1

A method of producing information indicative of the depth and orientation of an elongated object buried beneath the ground using electromagnetic radiation transmitted from and received by an antenna apparatus comprising mutually electrically orthogonal transmit and receive elements, said radiation being elliptically or circularly polarized or nearly so, said method comprising the following steps: (a) positioning an elongated reference object at known angular orientation with respect to a reference direction on the ground in a position to intercept radiation emitted from said antenna apparatus with the transmit and receive elements thereof in positions of known angular orientations with respect to the lengthwise direction of said reference object; (b) energizing the transmit elements of said apparatus with a first electric signal to cause radiation to be transmitted therefrom; (c) receiving radiation backscattered due to step (a) by means of said receive elements and producing first data corresponding to the received backscattered radiation; (d) storing said first data; (e) repositioning said transmit and receive elements at least once to new positions angularly separated from the immediately previous positions by a known angle other than an integer multiple of 90° about an axis transverse to the lengthwise direction of said reference object; (f) repeating steps (b), (c) and (d) after each repositioning effected by step (e) to obtain at least second data; (g) algebraically combining at least said stored first data and said second data to reduce clutter and errors due to departure from exact orthogonality of said transmit and receive elements upon each performance of step (f) and based on said algebraic combining producing reference data defining a known orientation of said reference object in relation to a known reference direction; (h) storing said reference data; (i) positioning said antenna apparatus over the ground with said transmit and receive elements in position at known angular orientations with respect to a reference direction on the ground; and (j) energizing said transmit elements with a signal identical to said first electrical signal to transmit radiation towards the ground; (k) receiving radiation back-scattered due to step (j) by means of said receive elements and producing third data corresponding to the received back-scattered radiation; (l) storing said third data; (m) repositioning of said transmit and receive elements at least once to new positions angularly separated from the previous positions by a known angle other than integer multiple of 90° about an axis directed into the ground; (n) repeating steps (j), (k), and (l) after each repositioning effected by step (m) to obtain fourth data; (o) algebraically combining at least said stored third data and fourth data to reduce clutter and errors due at least to departure from exact orthogonality of said transmit and receive elements and producing search data based on the algebraic combining of said third and fourth data; (p) storing said search data; and (q) detecting correlation between said stored reference data and said stored search data to yield said information and further to reduce clutter in said stored fourth data, said correlation being detected using a predetermined filtering technique; wherein steps (a)-(h) are optionally performed either before or after steps (i)-(p).

Claim 2

A method of producing information indicative of the depth and orientation of an elongated object buried beneath the ground using electromagnetic radiation transmitted from and received by an antenna apparatus comprising mutually electrically orthogonal transmit and receive elements, said radiation being elliptically or circularly polarized or nearly so, said method comprising the following steps: (a) positioning an elongated reference object at known angular orientation with respect to a reference direction on the ground in a position to intercept radiation emitted from said antenna apparatus with the transmit and receive elements thereof in positions of known angular orientations with respect to the lengthwise direction of said reference object; (b) energizing the transmit elements of said apparatus with a first electric signal to cause radiation to be transmitted therefrom; (c) receiving radiation backscattered due to step (a) by means of said receive elements and producing first data corresponding to the received backscattered radiation; (d) storing said first data; (e) repositioning said transmit and receive elements at least once to new positions angularly separated from the immediately previous positions by a known angle other than an integer multiple of 90° about an axis transverse to the lengthwise direction of said reference object; (f) repeating steps (b), (c) and (d) after each repositioning effected by step (e) to obtain at least second data; (g) algebraically combining at least said stored first data and said second data to reduce clutter and errors due to departure from exact orthogonality of said transmit and receive elements upon each performance of step (f) and based on said algebraic combining producing reference data defining a known orientation of said reference object in relation to a known reference direction; (h) storing said reference data; (i) positioning said antenna apparatus over the ground with said transmit and receive elements in position at known angular orientations with respect to a reference direction on the ground; and (j) energizing said transmit elements with a signal identical to said first electrical signal to transmit radiation towards the ground; (k) receiving radiation back-scattered due to step (j) by means of said receive elements and producing third data corresponding to the received back-scattered radiation; (l) storing said third data; (m) repositioning of said transmit and receive elements at least once to new positions angularly separated from the previous positions by a known angle other than integer multiple of 90° about an axis directed into the ground; (n) repeating steps (j), (k), and (l) after each repositioning effected by step (m) to obtain fourth data; (o) algebraically combining at least said stored third data and fourth data to reduce clutter and errors due at least to departure from exact orthogonality of said transmit and receive elements and producing search data based on the algebraic combining of said third and fourth data; (p) storing said search data; and (q) detecting correlation between said stored reference data and said stored search data to yield said information and further to reduce clutter in said stored fourth data, said correlation being detected using a predetermined filtering technique; wherein steps (a)-(h) are optionally performed either before or after steps (i)-(p).