The use of improvised explosive devices in the Iraq and Afghanistan conflicts has made clear that the ability to survey objects underground rapidly and effectively--essentially to see the unseen--is a critical requirement for safeguarding today's war fighter, as well as for making combat regions habitable once hostilities have ended. One approach to searching for IEDs is to use three-dimensional ground penetrating radar (GPR).
Until recently, 3-D GPR data acquisition was a time-consuming process that required multiple survey lines to be collected in a regular pattern. Now, a novel step-frequency GPR (SF GPR) system, using an advanced antenna array for high-resolution three-dimensional subsurface imaging, speeds and simplifies the use of 3-D GPR by eliminating the need for multiple passes while providing real-time visual data that lets the user immediately refine the search area and radar resolution used for searching.
The approach, employing a unique application of radio-wave-based step-frequency GPR, uses a multichannel radar array to enable single-pass 3-D analysis of underground artifacts in real-time, promising faster, simpler detection of IEDs in combat environments. A fielded SF GPR operates with a standoff antenna array to obtain maximum resolution at shallow depths, making the system suitable for detecting land mines and IEDs below the ground surface.
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| The GeoScope GPR step-frequency radar can generate waveforms from 100 MHz up to 3 GHz, providing as many as 1,160 frequencies with waveform lengths of 0.5 to 10 milliseconds. A coherent receiver means that the whole waveform length (typically a few milliseconds) is used as
100 percent efficient integration time. |
The 3-D advantage
Compared with two-dimensional approaches, 3-D is superior for scan- ning deep targets. The 3-D approach provides equivalent antenna gain to 2-D radar, along with 2-D's ability to correct for phase-front distortion on the surface. The added data set dimensionality enables the use of human data interpretation or artificial intelligence for target detection.
Three-dimensional mapping and imaging constitute an efficient tool for applications such as utility mapping, airfield inspection and construction planning. The horizontal time slices obtained through 3-D GPR show subsurface features and manmade objects that would be difficult to detect and describe using traditional vertical radargrams. By comparing the resulting 3-D GPR data with maps of the existing infrastructure, it is easy to distinguish between the known existing objects, such as pipes, and unknown objects.
