A UAV-based Radar Sounder SAR System for the Imaging of Internal Snow and Firn Stratifications

Abstract:
Unpiloted aerial vehicle (UAV)-based synthetic aperture radars (SAR) offer great potential for use in the structural mapping of snow and firn structures, such as crevasses or stratifications within the subsurface of alpine glaciers. Especially advantageous is the possibility to conduct autonomous and wide-area measurements of a glacier without the risk of crevasse fall or avalanches for ground-penetrating radar (GPR) operators. We present an imaging approach for the mapping of snow and firn structures based on a UAV-borne GPR system, capable of precisely accommodating the refraction effects at the surface. Several common methods for estimating the refraction at the dielectric interface for a planar surface are presented, and their performance is evaluated. As the topography of an alpine glacier is rarely planar, an imaging approach for arbitrary surfaces is presented, which relies on the extraction of the surface from the raw radar B-scan. Measurements from a sand pit experiment confirm the applicability of the imaging approach before the algorithm is applied to measurements from the Jungfraufirn glacier, Switzerland, highlighting the great potential of UAV-based GPR for use in future glacial research.