Mapping the Seaward Landfast Ice Edge (SLIE)
RADARSAT ScanSAR Wide Beam images are calibrated and georeferenced with SAR tools provided by the Alaska Satellite Facility. Mosaics are compiled from several images to cover the study area using ENVI’s IDL programming environment. The mosaics eliminate “no data” triangles between images in the study area regions but edge effects and backscatter variations are apparent.
Subscenes are created using IDL scripts which also smooth backscatter and edge effects.
The Seaward Landfast Ice Edge (SLIE) is derived using a techique that computes the difference between backscatter gradients of three consecutive mosaics of Radarsat data. The derived information is converted to ESRI’s ArcGIS grid format.
This chart shows the development of landfast ice through the winter of 2001-02 at 10 locations throughout the study area. Periods of growth, stability and break-up are clearly seen. It is noteworthy that different locations reach their peak landfast ice extent at different times.
Mapping Recurring Spring Leads
Advanced Very High Resolution Radiometer (AVHRR) scenes are cropped from the swath data.
Leads data are derived in a binarized format and converted to an ArcGIS grid.
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