Subsurface scattering of synthetic aperture radar signals assessed using ground-penetrating radar

Radar remote sensing techniques are becoming more widely applied in dryland regions, because the lower frequency Synthetic Aperture Radar (SAR) systems enable significant penetration into the subsurface under very dry conditions, allowing subsurface characteristics to be interpreted. Field experiments at two contrasting sites in the Libyan Fazzān show ground-penetrating radar (GPR) can be used to image the structural characteristics of duricrusts which generate backscatter differences. Site A consists of limited sedimentary layers and is relatively homogeneous in GPR response. Site B has multiple sedimentary layers and significant scatter in the form of multi-scale hyperbolae, from cavities, cracks, rocks and root nodules. Effective penetration depth is greater (> 3 m) at Site B and at the lower frequency. Using the mean instantaneous amplitude, Site B shows a high degree of signal scattering as a result of these different signal characteristics. Site B has a stronger GPR signal return by 42 % at 900 MHz. At 450 MHz this is reduced to 13 %, due to reduced sensitivity to smaller scatterers. At low SAR frequencies, subsurface scattering becomes important in determining backscatter. With increased subsurface complexity, SAR backscatter will increase. Therefore, in dry environments, backscatter models need to incorporate subsurface scattering effects if they are to more closely match SAR observations. sponding author. Email: [email protected] MBCharlton.com Research Notes w.publications.mbcharlton.com/ResearchNotes.html 2 M.B.Charlton and K.White MBCharlton.com Research Note 1 1 May 2008