GROUND-PENETRATING RADAR EXPERIMENTATION IN LOSSY SOIL CONDITIONS: EXAMPLES FROM IMAGING BURROWING CRAYFISH

Previous studies using ground-penetrating radar (GPR) to identify and image subsurface crayfish habitations have proven to be successful. Yet additional research is necessary to understand how antenna transmission frequency could improve the imaging resolution of burrows and the ability to delineate these burrows from the surrounding lossy soils. Unfortunately, burrowing crayfish by nature inhabit very moist, clay-rich soils, which makes traditional GPR methodologies rather difficult. Our team attempted to test multiple GPR systems with dominant frequency bandwidths that might successfully resolve a depth range of 0-2 m while maintaining suitable resolution for imaging tiny burrows. The 400 MHz, 900 MHz, and 350 MHz hyper-stacking (350HS) GPR systems were tested at multiple sites where observable crayfish activity was evident. The GPR data were processed using GPR Slice to produce 2D profiles and 3D images, horizontal depth slices, and isosurfaces. Preliminary results show greater penetration and higher resolution at depths of up to 2 m with the 350HS system compared to the 400 MHz unit. High-resolution results were obtained using the 400 MHz system, but the lossy soil conditions generated noise in the GPR data. Although the 900 MHz did not provide as suitable penetration to the depth range needed for this research, the 900 MHz antenna did provide high resolution imaging at a depth of 1m or less.