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Since
the SAR backscatter varies with ice type, snow cover, surface roughness and other
ice characteristics it is possible to classify an ERS-1 SAR image into several
ice types (see classified image to the right); the image has been acquired on
5-3-1992. Two principles can be applied: one is to use calibrated backscatter values for each individual pixel, and the other is to use textural information in the image. The first principle requires knowledge about the relation between SAR parameters (frequency, polarization, incidence angle) and ice type/surface characteristics. Such relations have been established through a series of validation experiments. Textural classification can be used as a supplement to backscatter levels. None of these methods are fully automatic. Reliable classification requires manual analysis by an expert.
During the ERS-1 experiments in the Greenland Sea and the Barents Sea SAR signatures of different ice types were studied, in particular during winter conditions. The ice class table shows the ERS-1 SAR backscatter intervals for most important ice types, established from the validation experiments.
These backscatter intervals are used to classify the SAR image.
NERSC, Bergen, Norway
Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry