6
C. TSATSOULIS AND R. KWOK
data to obtain fields of these variables are in various stages of maturity. Algorithms for
tracking common features in sequential SAR imagery are quite well-developed within the
perennial ice zone, but better algorithms are required to increase our confidence in the
results from the ice margins and coastal regions. The advantage of ice motion measurements is that a thorough understanding of backscatter signatures of sea ice is not
required. We can observe ice motion at the S-krn scale with the resolution of the SAR data
that is currently available. Extraction of ice type and concentration from SAR data is a
more involved matter: the classification of the principal ice types (first-year, multiyear)
in SAR data has met with varying degrees of success. In situ validation of ice type algorithms is difficult due to the extent of coverage and the variability of ice types within the
ice cover. Overlapping signatures of new ice and old ice confound most algorithms which
expect some invariance of backscatter. In summer, the contrasts between ice types are lost
due to melt and the appearance ofliquid water on the surface. Further work in these areas
is required. Perhaps one of more simple, yet useful, procedures is the one that detects the
onset of melt and freeze- up. The changes in the ice backscatter during these seasonal transition are quite dramatic. Intensive validation of these algorithms, however, would require
a fairly long time series of SAR observations and supporting data. The importance of correlative datasets (e.g., temperature, wind, etc.) for improvement and validation of SAR
data analysis algorithms cannot be overemphasized. Some investigators have moved in
the direction of fusion of datasets from different remote sensing instruments. It is the
intent of this book to survey some of the algorithms and procedures used to measure of
these sea ice variables.
1.4
This Book
The chapters in this volume contain the results of recent research on algorithms for
analyses of SAR data on sea ice. All algorithms and analyses in this book are aimed at
the measurement of specific sea ice parameters: the chapters discuss the significance
of the polar geophysical phenomena that are being measured and analyzed. In addition to chapters describing SAR data analysis, one chapter discusses the needs and capabilities of the operational community which supplies time-critical SAR analyses to the
maritime industry, and another one describes the US processing and archival SAR center, the Alaska SAR Facility, which will produce raw SAR data and high level geophysical products. A brief summary of each chapter follows.
The first half of the book (Chaps. 2-8) is dedicated to SAR data analysis and the second part of the book (Chaps. 9-12) is dedicated to SAR polar systems and facilities.
Chapter 2, by L.-K. Soh, B. Holt, and C. Tsatsoulis, describes an algorithm that segments SAR images of the marginal ice zone and identifies the ice floes present in them.
The algorithm implements a novel technique that combines mathematical morphology with statistical segmentation to identify floes and separate them when they are
touching. Next, the chapter discusses how measurements of the floe size distributions
can be used as a proxy for climatological and geophysical processes, and presents a large
study of floe measurements in the Arctic.
Chapter 3, by D.G. Barber, A. Thomas, and T.A. Papakyriakou, presents our current
understanding of how SAR may be used in estimating components of the surface energy balance within the marine cryosphere, and describes various statistical linkages
C. TSATSOULIS AND R. KWOK
data to obtain fields of these variables are in various stages of maturity. Algorithms for
tracking common features in sequential SAR imagery are quite well-developed within the
perennial ice zone, but better algorithms are required to increase our confidence in the
results from the ice margins and coastal regions. The advantage of ice motion measurements is that a thorough understanding of backscatter signatures of sea ice is not
required. We can observe ice motion at the S-krn scale with the resolution of the SAR data
that is currently available. Extraction of ice type and concentration from SAR data is a
more involved matter: the classification of the principal ice types (first-year, multiyear)
in SAR data has met with varying degrees of success. In situ validation of ice type algorithms is difficult due to the extent of coverage and the variability of ice types within the
ice cover. Overlapping signatures of new ice and old ice confound most algorithms which
expect some invariance of backscatter. In summer, the contrasts between ice types are lost
due to melt and the appearance ofliquid water on the surface. Further work in these areas
is required. Perhaps one of more simple, yet useful, procedures is the one that detects the
onset of melt and freeze- up. The changes in the ice backscatter during these seasonal transition are quite dramatic. Intensive validation of these algorithms, however, would require
a fairly long time series of SAR observations and supporting data. The importance of correlative datasets (e.g., temperature, wind, etc.) for improvement and validation of SAR
data analysis algorithms cannot be overemphasized. Some investigators have moved in
the direction of fusion of datasets from different remote sensing instruments. It is the
intent of this book to survey some of the algorithms and procedures used to measure of
these sea ice variables.
1.4
This Book
The chapters in this volume contain the results of recent research on algorithms for
analyses of SAR data on sea ice. All algorithms and analyses in this book are aimed at
the measurement of specific sea ice parameters: the chapters discuss the significance
of the polar geophysical phenomena that are being measured and analyzed. In addition to chapters describing SAR data analysis, one chapter discusses the needs and capabilities of the operational community which supplies time-critical SAR analyses to the
maritime industry, and another one describes the US processing and archival SAR center, the Alaska SAR Facility, which will produce raw SAR data and high level geophysical products. A brief summary of each chapter follows.
The first half of the book (Chaps. 2-8) is dedicated to SAR data analysis and the second part of the book (Chaps. 9-12) is dedicated to SAR polar systems and facilities.
Chapter 2, by L.-K. Soh, B. Holt, and C. Tsatsoulis, describes an algorithm that segments SAR images of the marginal ice zone and identifies the ice floes present in them.
The algorithm implements a novel technique that combines mathematical morphology with statistical segmentation to identify floes and separate them when they are
touching. Next, the chapter discusses how measurements of the floe size distributions
can be used as a proxy for climatological and geophysical processes, and presents a large
study of floe measurements in the Arctic.
Chapter 3, by D.G. Barber, A. Thomas, and T.A. Papakyriakou, presents our current
understanding of how SAR may be used in estimating components of the surface energy balance within the marine cryosphere, and describes various statistical linkages