Airborne surface roughness and sea ice thickness measurements during CCGS Henry Larsen cruise: Canadian Arctic Through flow (CATs) 2009

It takes advantage of the fact that the helicopter height variations are only at low frequencies, whereas the surface roughness is a superimposed, high frequency signal. The resulting ice morphology is obtained relative to the surface of the surrounding level ice. Absolute freeboard, i.e. the height of the surface above the water level, cannot be obtained unless the helicopter height variations are independently determined by means of differential GPS and Inertial navigation systems.

The resulting surface profiles can be used to identify pressure ridges, e.g. by a Rayleigh criterion. By this criterion only local maxima which are twice as high as the surrounding local minima are defined as pressure ridges.