GPR images of hidden crevasses in Antarctica

We have used airborne and ground-based GPR at 400-500 MHz to image hidden crevasses in Antarctica. The radar antennas were either pushed in front of a snowmobile, or cantilevered from a helicopter flying at about 6 m altitude and speeds near 15 m/s. We used a high trace acquisition rate, long time ranges, and migration to show snow bridge depth, crevasse width, septums between crevasses, connecting cavities and associated folded strata in the ground-based profiles. The crevasse images are formed by the discontinuities in reflections from the stratified firn. Diffractions from crevasse walls are strongly single-sided, originate from point and linear discontinuities, and provide advance warning. Airborne recorded images are similar, but less detailed than surface images. An increased trace rate could improve airborne imaging and allow greater profile speeds.