CHAPTER 2
Identifying Ice Floes and Computing Ice Floe Distributions
in SAR Images
L.-K. SOH, C. TSATSOULIS, AND B. HOLT
Contents
2.1 Introduction
9
2.2 Background
10
2.3 The Restricted Growing Concept ....................................
11
2.3.1 Initial Segmentation ..............................................
12
2.3.2 Probabilistic Labeling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
2.3.3 Morphological Cleaning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15
2.4 Ice Floe Algorithm and Results ......................................
17
2.5 Preliminary Results of an Arctic Summer Time Series Study. . . . . . . . . . . . .
22
2.6 Summary and Conclusions .........................................
31
References ...........................................................
32
2.1
Introduction
Sea ice that grows in the open seas takes on characteristic forms and shapes that are
different from the largely smooth sea ice that grows in calm inlets, for example. Forcing from wind and waves fractures the thickening ice into pieces or floes, which then
collide with each other. Over a winter season, the resulting sea ice matrix consists of
fairly rounded floes with deformed surfaces composed of ridges and hummocks, separated by open water areas or leads. The new ice that forms in leads cements the floes
together into an aggregate floe, which moves as a larger rigid piece composed of many
smaller floes. In the summer, aggregated floes disintegrate as the thinner ice "cement"
preferentially melts, making the isolated floes easily identifiable.
In studies of the polar regions with satellite imagery, including synthetic aperture
radar (SAR) imagery, identification of ice floes and their outlines is important for
examining both large- and small-scale processes (Rothrock and Thorndike 1984; Burns
et al. 1987; Campbell et al.1987). Most floe-related issues of interest are in the areas of
classification (Haverkamp et al. 1995), registration and motion tracking (Fily and
Rothrock 1986, 1987; Vesecky et al.1988; Banfield 1991; Kwok et al.1991; McConnell et al.
1991), route planning (see for example a navigation scheme based on object avoidance,
Holmes and Jungert 1992), floe size measurements (Hall and Rothrock 1987; Korsnes
Analysis of SAR Data of the Polar Oceans
Edited by C. Tsatsoulis and R. Kwok
© Springer-Verlag Berlin Heidelberg 1998
Identifying Ice Floes and Computing Ice Floe Distributions
in SAR Images
L.-K. SOH, C. TSATSOULIS, AND B. HOLT
Contents
2.1 Introduction
9
2.2 Background
10
2.3 The Restricted Growing Concept ....................................
11
2.3.1 Initial Segmentation ..............................................
12
2.3.2 Probabilistic Labeling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
2.3.3 Morphological Cleaning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15
2.4 Ice Floe Algorithm and Results ......................................
17
2.5 Preliminary Results of an Arctic Summer Time Series Study. . . . . . . . . . . . .
22
2.6 Summary and Conclusions .........................................
31
References ...........................................................
32
2.1
Introduction
Sea ice that grows in the open seas takes on characteristic forms and shapes that are
different from the largely smooth sea ice that grows in calm inlets, for example. Forcing from wind and waves fractures the thickening ice into pieces or floes, which then
collide with each other. Over a winter season, the resulting sea ice matrix consists of
fairly rounded floes with deformed surfaces composed of ridges and hummocks, separated by open water areas or leads. The new ice that forms in leads cements the floes
together into an aggregate floe, which moves as a larger rigid piece composed of many
smaller floes. In the summer, aggregated floes disintegrate as the thinner ice "cement"
preferentially melts, making the isolated floes easily identifiable.
In studies of the polar regions with satellite imagery, including synthetic aperture
radar (SAR) imagery, identification of ice floes and their outlines is important for
examining both large- and small-scale processes (Rothrock and Thorndike 1984; Burns
et al. 1987; Campbell et al.1987). Most floe-related issues of interest are in the areas of
classification (Haverkamp et al. 1995), registration and motion tracking (Fily and
Rothrock 1986, 1987; Vesecky et al.1988; Banfield 1991; Kwok et al.1991; McConnell et al.
1991), route planning (see for example a navigation scheme based on object avoidance,
Holmes and Jungert 1992), floe size measurements (Hall and Rothrock 1987; Korsnes
Analysis of SAR Data of the Polar Oceans
Edited by C. Tsatsoulis and R. Kwok
© Springer-Verlag Berlin Heidelberg 1998