3-D radar data-capture innovation makes IEDs easier to spot

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.

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.