Alpine snow depth measurements from aerial FMCW radar

Snow depth was measured with an L-band frequency-modulated continuous wave (FMCW) radar operating from an aerial tramway up to 70 m above the ground. Snow depth, wetness, and slope varied greatly along the 2.4-km transect, with 640 m of relief. Radar measurements taken in the morning, when the snowpack was frozen were compared against concurrent manual depth probes, and good agreement was found between the estimates. The results suggest that deep snowpacks in rugged terrain can be accurately and safely surveyed by helicopter-borne radar.