USING A HELICOPTER-BORNE EM-INDUCTION SYSTEM TO VALIDATE RADARSAT SEA ICE SIGNATURES
Field surveys over the past several winters in the Gulf of St. Lawrence and off Labrador use helicopter-borne sensors to validate SAR ice signatures in RADARSAT imagery. Ice-plus-snow thickness profiles were collected using an electromagnetic (EM) induction system towed 15-25m above the ice surface...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.488.3789 http://starfish.mar.dfo-mpo.gc.ca/science/ocean/seaice/Publications/peterson06.pdf |
| Summary: | Field surveys over the past several winters in the Gulf of St. Lawrence and off Labrador use helicopter-borne sensors to validate SAR ice signatures in RADARSAT imagery. Ice-plus-snow thickness profiles were collected using an electromagnetic (EM) induction system towed 15-25m above the ice surface by helicopter. Measurements from the laser altimeter contained in the EM system were high-pass filtered to derive ice surface topography profiles. In RADARSAT images, changes in SAR backscatter values are usually associated with changes in EM-measured ice thickness and laser-measured surface roughness. For example in the Gulf of St. Lawrence, large floes having low SAR backscatter are associated with uniform EM-measured ice thicknesses of 30-50 cm, while more variable ice thicknesses are present in the surrounding areas having higher backscatter. EM-measured ice thicknesses representing both deformed and undeformed ice are 50 % higher than ice thicknesses obtained through augered ice holes in undeformed ice. In a SAR image of the Labrador shelf area, the inshore ice appears dark, with bright streaks visible southeast (downwind) of small coastal islands. These streaks correspond to ice rubble with EM-measured ice thicknesses of about 1-2 m and laser-measured ridge elevations up to 0.9 m. 1. |
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