The combination of laser and radar altimetry could provide an estimate of snow depth in regions such as the percolation zone, where the radar measurement is dominated by the return signal from the most recent annual ice layer and the laser return is from the snow surface. Studies with radar echo soundings suggest that a high correlation exists between surface elevation and bedrock topography. He noted that sastrugi topography grows with time after a blizzard. He discussed the scale of surface topography in terms of the vertical and horizontal size of the features as well as their temporal stability. He noted the need for a long-term data set, but also noted the importance of initiating the collection of essential measurements.
Submerging areas erode quickly because of permafrost changes.
He made the observation that when GLAS is launched, the data collected in the airborne laser altimeter will provide data sets spanning 10 years over particular regions of the ice sheet. The combination of aircraft data and GLAS will provide an early assessment of mass balance in those regions. The laser footprint of 100 m is similar to the GLAS footprint of 70 m. The DEMs have high resolution of a few tens of centimeters and were created from parallel AOL swaths measured along a selected ERS-1 ground track. The proposed technique may be applicable to GLAS calibration as well.