[1] Sea ice concentration is measured by satellites, with the Special Sensor Microwave Imager / Sounder (SSMIS), and the European Space Agency's Cryosat-2 satellite to map the thickness and shape of the Earth's polar ice cover.
It is also important for navigators on icebreakers since there is an upper limit to the thickness of ice any ship can sail through.
Since 85–95% of snow-free sea ice is usually located below the waterline, the computation of the thickness is fairly simple;[3] however, accurate measurement of ice freeboard is hindered by several factors including snow cover, and modeling of this data is being constantly improved.
The Ice, Cloud, and land Elevation Satellite (ICESat), measured ice sheet mass balance, cloud and aerosol heights, and land topography and vegetation characteristics, with an active service period from February 2003 to October 2009.
The E-M Bird ice thickness meter, designed by the Alfred Wegener Institute for Polar and Marine Research, is carried aloft by helicopter and measures ice thickness with a combination of a pair of inductance coils that measure the ice-water interface based inductance variations—similar to a metal detector—and a laser altimeter which measures the ice surface.