High Resolution Visualization of Snow and Ice via Circular Synthetic Aperture Radar Techniques

Abstract:

High resolution three-dimensional measurements of snow and ice properties obtained

through non-destructive methods are greatly needed to better understand many natural

processes related to snow hydrology, avalanche forecasting, and snow/sea ice interactions.

Such visualizations could be useful in detecting snow stratigraphy and composition, liquid water

percolation and volume, and snow/ice interfaces. Here, we present the application of a circular

synthetic aperture radar system (CSAR) that can remotely scan and reconstruct a three-

dimensional image of such targets utilizing a low-power and portable ultra-wide-band (UWB)

7.29 GHz radar system. UWB radar transmits in a wide spectrum that makes it ideal for

detecting targets smaller than 5 cm. Although CSAR has been used previously to image other

inanimate three-dimensional objects as an exercise, it has yet to be applied to the cryosphere

and/or operationalized for this purpose. Utilizing cold laboratory experiments, we have

developed a back projection algorithm that allows for high resolution reconstruction of a target’s

reflectance within the radar’s main lobe path. Using a mechanized turntable, we have been able

to visualize various geometries of reflective and asymmetric objects after rotating them through

a 360 degree circular track. The reflected returns are then post-processed using our back-

projection algorithm. This algorithm takes a sum of radar signal returns across the entire 360

degree scanning region corresponding to x,y locations. The sum of x,y locations are returned as

a 2D heatmap image. This process allows reflectivities corresponding to different materials or

geometries to register in a spatially recognizable image. Further analysis of this back-projection

allows for a 3D analysis of the z dimension as well. Currently, we are working to apply this x,y,z

back-projection with CSAR to various multi-phase snow microstructures from within a controlled

laboratory environment, before deploying to the field for further testing and analysis.