Abstract
An approach for identification of sea ice types in spaceborne synthetic aperture radar (SAR) image data is presented. The unsupervised classification approach involves cluster analysis for segmentation of the image data followed by cluster labeling based on previously defined look‐up tables containing the expected backscatter signatures of different ice types measured by land‐based scatterometer. The particular look‐up table used for labeling a segmented image is selected based on the seasonal and meteorological conditions at the time of data acquisition. The extensive scatterometer observations and experience accumulated in field campaigns during the last 10 years were used to construct these look‐up tables. These tables are expected to evolve as sea ice observations from the European ERS‐1 SAR become available. This paper presents the classification approach, its expected performance, the dependence of this performance on radar system performance, and expected ice scattering characteristics. Results using both aircraft and simulated ERS‐1 SAR data are presented. The results are compared to limited field ice property measurements and coincident passive microwave imagery. An algorithm based on this experimental approach has been implemented in the geophysical processor system at the Alaska SAR Facility for classification of sea ice data in ERS‐1 C band SAR data. The importance of an integrated postlaunch program for validation and improvement of this approach is discussed.
Highlights
The derivation of valuable information on sea ice properties from radar imagery has increased steadily over the last decade [Carsey, 1989]
This paper focuses on the ice classification algorithm which has been implemented at Alaska SAR Facility (ASF) to generatethesemaps of ice type and concentration, first from ERS-1 and the evolution of such an algorithm with the introduction of ancillary data sets(suchas passivemicrowave observations) and the upcoming JERS-1 and RADARSAT
We show results of sample simulations and comparison of the aircraft imagery with KRMS and the limited surface measurements obtained from a field camp that was overflown by the DC-8 during March 1988
Summary
The derivation of valuable information on sea ice properties from radar imagery has increased steadily over the last decade [Carsey, 1989]. 0148-0227/92/91JC-02652505.00 image analysis approaches have been applied to the ice signaturesto examine the types of information available in the SAR imagery for the automatic extraction of ice types [e.g., Lyden et al, 1984; Wackerman et al, 1988] These SAR studies of sea ice have examined imagery obtainedfrom aircraft and spaceborneSAR systems,usually in combination with other sensors, in situ measurements of ice and snow conditions, and near-surface scatterometer and radiometer measurements.The radars have operated over a wide range of frequencies, incidence angles, and polarizations. During this decade, single-channel spaceborne SARs are to be launched on the European ERS-1 in 1991, the Japanese ERS-1 in 1992, and the Canadian RADARSAT in 1994. The key observations are presented with a brief discussion of the importance of an integrated effort required to validate the performance and quality of such an algorithm
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