Mobile coherent change detection ground penetrating radar

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.

What is claimed is: 
     
         1 . 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.   
     
     
         2 . The apparatus of  claim 1  wherein the enclosure has an inner surface comprising a material that attenuates radiation emitted from the antenna elements. 
     
     
         3 . The apparatus of  claim 2  wherein the material that attenuates radiation is a ferrite material. 
     
     
         4 . The apparatus of  claim 1  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. 
     
     
         5 . The apparatus of  claim 4  wherein the center-frequency wavelength of the transmitted radar signals is an effective wavelength for a pulse duration of the transmitted radar signals. 
     
     
         6 . The apparatus of  claim 1  wherein each of the antenna elements is a resistively-loaded antenna element.