Signal processing methods for ground penetrating radar from elevated platforms

• US 7,528,762 B2
• Filed: 03/30/2006
• Issued: 05/05/2009
• Est. Priority Date: 03/31/2005
• Status: Expired due to Fees

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Cerwin, Stephen A.
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): GALT, CASSI J
• Application Number:
  US11/278,056
• Publication Number:
  US 20070024489A1
• Time in Patent Office: 1,132 Days
• Field of Search: 342/22, 342/25.C, 342/25.R, 342/159, 342/90, 342/179, 324/330, 324/332
• 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 ground penetrating radar (GPR) signals transmitted from an airborne platform into the ground and reflected from an object or feature in the ground, comprising:

selecting a frequency for the signal, based on characteristics of the ground and a desired depth of penetration of the signal into the ground;

wherein the frequency is in the range of 1 MHz to 1 GHz;

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 frequency and selected wave angle;

acquiring a first set of signal return data from a vertically polarized GPR signal, and simultaneously or nearly simultaneously acquiring a second set of signal return data from a horizontally polarized GPR signal;

differencing the first set of signal return data and the second set of signal return data, such that data resulting from surface reflections are cancelled from the differenced data; and

analyzing the non-cancelled data to determine data representing subsurface reflections of the vertically polarized GPR signal and the horizontally polarized GPR signal, thereby obtaining data representing subsurface features.

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

3. The method of claim 1, wherein the inspection platform is a helicopter having antennas on the tips of both rotor blades and are configured to inspect the ground directly under the helicopter.