Signal Processing Methods for Ground Penetrating Radar from Elevated Platforms

• US 20070024489A1
• Filed: 03/30/2006
• Published: 02/01/2007
• Est. Priority Date: 03/31/2005
• Status: Active Grant

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Cerwin, Stephen
• Granted Patent: US 7,528,762 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 13/9027 Pattern recognition for feature extraction
• CPC Class Codes: G01S 13/904 SAR modes
• CPC Class Codes: G01S 13/9076 Polarimetric features in SAR
• CPC Class Codes: G01S 13/9082 Rotating SAR [ROSAR]
• CPC Class Codes: G01S 7/024 using polarisation effects in waveguides H01P1/165; for aerials H01Q, e.g. H01Q15/22, H01Q15/24, H01Q19/195
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005
• CPC Class Codes: G01V 3/17 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

Methods and systems for using ground penetrating radar (GPR) to obtain subsurface images. The depression angle, frequency, and polarization can all be adjusted for the soil conditions at hand. In particular, the depression angle is set at the “pseudo-Brewster angle” for improved ground penetration.

Claims

1. A method of improving the data from GPR signals reflected from an object or feature in the ground, comprising:

selecting a first frequency for the signal, based on characteristics of the ground;

selecting a wave angle for the signal that minimizes the reflection coefficient for the signal at the interface between air and the ground;

at the selected first frequency and selected wave angle;

acquiring signal return data from a vertically polarized GPR signal, and acquiring signal return data from a horizontally polarized GPR signal; and

differencing the signal return data, thereby obtaining improved subsurface detail in the data.

2. The method of claim 1, wherein the differencing is performed using a coherent differencing method.

3. The method of claim 1, further comprising acquiring signal return data from a vertically polarized GPR signal at a second frequency;

and differencing the data from the signals at the first frequency and the second frequency, using a second differencing process.

4. The method of claim 3, wherein the second differencing process is a coherent differencing process.

5. The method of claim 3, wherein the second differencing process is an incoherent differencing process.

6. The method of claim 1, wherein the method is performed by using at least one radar transmitting and receiving device mounted on the tip of a rotor blade of a rotor aircraft.

7. A method of improving the data from GPR signals reflected from an object or feature in the ground, comprising:

selecting a first frequency for the signal, based on characteristics of the ground;

selecting a wave angle for the signal that minimizes the reflection coefficient for the signal at the interface between air and the ground;

selecting a second frequency for the signal, wherein at the second frequency, the selected wave angle has substantially the same reflection coefficient;

at the selected wave angle;

acquiring signal return data from a GPR signal at the first frequency, and acquiring signal return data from a GPR signal at the second frequency; and

differencing the signal return data, thereby obtaining improved subsurface detail in the data.

8. The method of claim 7, wherein the differencing is performed using a coherent differencing method.

9. The method of claim 7, wherein the second differencing process is an incoherent differencing process.

10. The method of claim 7, further comprising at the selected wave angle:

acquiring signal return data from a GPR signal at any frequency wherein the return data has substantially the same reflection coefficient at vertical polarization, and acquiring signal return data from a GPR signal at that frequency at horizontal polarization; and

differencing these two signals to obtain difference data.

11. The method of claim 10, wherein the differencing is performed using a coherent differencing method.

12. The method of claim 7, wherein the method is performed by using at least one radar transmitting and receiving device mounted on the tip of a rotor blade of a rotor aircraft.

13. A method of improving the data from GPR signals reflected from an object or feature in the ground, comprising:

selecting a first frequency for the signal, based on characteristics of the ground;

selecting a first wave angle for the signal that minimizes the reflection coefficient for the signal at the interface between air and the ground;

acquiring signal return data from a vertically polarized GPR signal at the selected first frequency and first wave angle;

selecting a second wave angle for the signal that is sufficiently different from the first wave angle to provide a measurable difference in reflection coefficient;

acquiring signal return data at the first frequency and second wave angle; and

differencing the signal return data, thereby obtaining improved subsurface detail in the data.

14. A method of improving the data from GPR signals reflected from an object or feature in the ground, comprising:

selecting a first set of signal values for signal parameters from the group of;

wave angle, frequency, and polarization;

acquiring signal return data from a GPR signal having the first set of signal values;

changing a value for one of the parameters, thereby resulting in a second set of signal values;

acquiring signal return data from a GPA signal having the second set of signal values;

differencing the signal return data, thereby obtaining difference data; and

using the difference data to detect subsurface features.