MOBILE COHERENT CHANGE DETECTION GROUND PENETRATING RADAR

• US 20130050008A1
• Filed: 08/30/2011
• Published: 02/28/2013
• Est. Priority Date: 08/30/2011
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Atkins, Robert George, Brooke, Justin J., Cornick, Matthew Tyler, Zhang, Beijia
• Granted Patent: US 8,786,485 B2
• Time in Patent Office: Days
• US Class Current: 342/22
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01S 7/027 Constructional details of housings, e.g. form, type, material or ruggedness
• CPC Class Codes: G01S 7/295 Means for transforming co-ordinates or for evaluating data, e.g. using computers

Abstract

Described are a method and system for detecting and locating changes in an underground region. Changes are detected using a mobile coherent change detection ground penetrating radar (GPR). The GPR system is located on a mobile platform that makes two more measurement passes over the same route to acquire GPR images of an underground region at different times. A lateral offset between the GPR images for the two different times is determined and applied to one of the GPR images to generate a GPR shifted image that is spatially aligned with the other GPR image using a correlation process or other technique. A GPR difference image is generated from the GPR shifted image and the other GPR image. The GPR difference image includes data representative of changes to the underground region that occurred between the two measurement passes.

Claims

1. A system for detecting and locating changes in an underground region, comprising:

a mobile ground penetrating radar (GPR) system having a linear array of antenna elements each configured to transmit a radar signal into an underground region and to receive a return radar signal from the underground region, an electromagnetic field generated by each antenna element during transmission being substantially the same as an electromagnetic field generated by each of the other antenna elements during transmission and an antenna receive pattern of each antenna element during reception being substantially the same as an antenna receive pattern of each of the other antenna elements during reception;

a radar processor in communication with the GPR system and configured to generate a GPR image of an underground region; and

a registration module in communication with the radar processor and configured to determine a lateral offset of the linear array between a pass over the underground region at a first time and a pass over the underground region at a second time, the registration module configured to spatially align a GPR image acquired for the first time and a GPR image acquired for the second time, and to generate a GPR difference image based on the spatially aligned GPR images, wherein the GPR difference image includes data representative of changes to the underground region that occur between the first and second times.

2. The system of claim 1 wherein the registration module comprises a correlation processor to determine the lateral offset from the GPR images at the first and second times.

3. The system of claim 1 wherein the registration module comprises a differential global positioning system (GPS) receiver.

4. The system of claim 1 wherein the antenna elements are resistively-loaded elements.

5. The system of claim 1 wherein a spacing of the antenna elements on the array does not exceed one-tenth of a center-frequency wavelength of the transmitted radar signal.

6. The system of claim 5 wherein the center-frequency wavelength of the transmitted radar signal is an effective wavelength for a pulse duration of the transmitted radar signal.

7. The system of claim 1 wherein the radar signal has a frequency in a VHF frequency range.

8. A method for determining a change to an underground region, comprising:

acquiring a ground penetrating radar (GPR) image of an underground region at a first time;

acquiring a GPR image of the underground region at a second time;

determining a lateral offset between the GPR images at the first and second times;

applying the lateral offset to one of the GPR images to generate a GPR shifted image; and

generating a GPR difference image based on the GPR shifted image and the other of the GPR images, wherein the GPR difference image includes data representative of changes to the underground region that occur between the first time and the second time.

9. The method of claim 8 wherein the determining of the lateral offset comprises performing an image correlation of the GPR images.

10. The method of claim 8 wherein the determining of the lateral offset comprises determining a difference in differential global positioning system data for a location of a GPR system that acquires the GPR image at the first time and the location of the GPR system when acquiring the GPR image at the second time.

11. The method of claim 8 further comprising squaring image data of the GPR difference image and integrating the squared image data in depth.

12. An apparatus for detecting and locating changes in an underground region, comprising:

a linear array of antenna elements each configured to transmit a radar signal into an underground region and to receive a return radar signal from the underground region, an electromagnetic field generated by each antenna element during transmission being substantially the same as an electromagnetic field generated by each of the other antenna elements and an antenna receive pattern of each antenna element during reception being substantially the same as an antenna receive pattern of each of the other antenna elements; and

an enclosure substantially surrounding the linear array of antenna elements and comprising a material that attenuates radiation emitted from the antenna elements during transmission, the enclosure configured to pass the radar signals from the antenna elements and to pass the return radar signals from the underground region.

13. The apparatus of claim 12 wherein the enclosure has an inner surface comprising a material that attenuates radiation emitted from the antenna elements.

14. The apparatus of claim 13 wherein the material that attenuates radiation is a ferrite material.

15. The apparatus of claim 12 wherein a spacing of the antenna elements in the linear array does not exceed one-tenth of a center-frequency wavelength of the transmitted radar signals.

16. The apparatus of claim 15 wherein the center-frequency wavelength of the transmitted radar signals is an effective wavelength for a pulse duration of the transmitted radar signals.

17. The apparatus of claim 12 wherein each of the antenna elements is a resistively-loaded antenna element.