Late-summer sea ice segmentation with multi-polarisation SAR features in C and X band

Ane S Fors,Torbjørn Eltoft,Angelika H H Renner,Anthony P Doulgeris,Sebastian Gerland,Camilla Brekke

doi:10.5194/tc-10-401-2016

Abstract

Abstract. In this study, we investigate the potential of sea ice segmentation by C- and X-band multi-polarisation synthetic aperture radar (SAR) features during late summer. Five high-resolution satellite SAR scenes were recorded in the Fram Strait covering iceberg-fast first-year and old sea ice during a week with air temperatures varying around 0 °C. Sea ice thickness, surface roughness and aerial photographs were collected during a helicopter flight at the site. Six polarimetric SAR features were extracted for each of the scenes. The ability of the individual SAR features to discriminate between sea ice types and their temporal consistency were examined. All SAR features were found to add value to sea ice type discrimination. Relative kurtosis, geometric brightness, cross-polarisation ratio and co-polarisation correlation angle were found to be temporally consistent in the investigated period, while co-polarisation ratio and co-polarisation correlation magnitude were found to be temporally inconsistent. An automatic feature-based segmentation algorithm was tested both for a full SAR feature set and for a reduced SAR feature set limited to temporally consistent features. In C band, the algorithm produced a good late-summer sea ice segmentation, separating the scenes into segments that could be associated with different sea ice types in the next step. The X-band performance was slightly poorer. Excluding temporally inconsistent SAR features improved the segmentation in one of the X-band scenes.

Highlights

A decline in the Arctic sea ice extent has been observed during the last decades, together with a large reduction in sea ice thickness and sea ice volume (Kwok et al, 2009; Parkinson and Comiso, 2013; Laxon et al, 2013; Meier et al, 2014)
The features in C band are based on the full covariance matrix, while those in X band are based on reduced covariance matrices as the TS-X scenes are dual polarisation scenes
We examined the potential of sea ice segmentation by C- and X-band multi-polarisation Synthetic aperture radar (SAR) features during late summer in the Fram Strait

Summary

Introduction

A decline in the Arctic sea ice extent has been observed during the last decades, together with a large reduction in sea ice thickness and sea ice volume (Kwok et al, 2009; Parkinson and Comiso, 2013; Laxon et al, 2013; Meier et al, 2014). Synthetic aperture radar (SAR) is widely used in operational sea ice monitoring. Operating in the microwave frequency, SAR has the advantage of providing all-weather and day-and-night imagery. Operational sea ice services use single and dual polarimetric SAR images (HH+HV or VH+VV) in sea ice monitoring due to their wide swath widths and good temporal coverage. On a local scale, more information and improved sea ice segmentation can be retrieved from full polarimetric SAR imagery (HH + HV + VH + VV). Today, such data are in limited use mainly due to its reduced coverage. The recent development of compact polarimetry could open the way for more polarimetric radar information to be retrieved at larger swath widths (Raney, 2007; Dabboor and Geldsetzer, 2014)

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Conclusion