On the Detection and Long-Term Path Visualisation of A-68 Iceberg

Ludwin Lopez-Lopez,Flavio Parmiggiani,Miguel Moctezuma-Flores,Lorenzo Guerrieri

doi:10.3390/rs13030460

Ludwin Lopez-Lopez, Flavio Parmiggiani + Show 2 more

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https://doi.org/10.3390/rs13030460

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Abstract

The article presents a methodology for examining a temporal sequence of synthetic aperture radar (SAR) images, as applied to the detection of the A-68 iceberg and its drifting trajectory. Using an improved image processing scheme, the analysis covers a period of eighteen months and makes use of a set of Sentinel-1 images. A-68 iceberg calved from the Larsen C ice shelf in July 2017 and is one of the largest icebergs observed by remote sensing on record. After the calving, there was only a modest decrease in the area (about 1%) in the first six months. It has been drifting along the east coast of the Antarctic Peninsula, and is expected to continue its path for more than a decade. It is important to track the huge A-68 iceberg to retrieve information on the physics of iceberg dynamics and for maritime security reasons. Two relevant problems are addressed by the image processing scheme presented here: (a) How to achieve quasi-automatic analysis using a fuzzy logic approach to image contrast enhancement, and (b) The use of ferromagnetic concepts to define a stochastic segmentation. The Ising equation is used to model the energy function of the process, and the segmentation is the result of a stochastic minimization.

Highlights

Weather conditions and seasonal variations impose restrictions on the monitoring of Antarctica by satellite remote sensing
The Fuzzy parameter q was fixed at 0.6, but acceptable results are obtained with 0.5 ≤ q ≤ 0.8, and in this case, the histogram information is distributed in the middle range
In order to evaluate its performance, the applied Fuzzy algorithm was compared with alternative contrast solutions: (a) the contrast limited adaptive histogram equalization (CLAHE) [30], and (b) the exponential grey-scale transformation

Summary

Introduction

Weather conditions and seasonal variations impose restrictions on the monitoring of Antarctica by satellite remote sensing. Continuous sunlight from December to February makes it a good period for optical image remote sensing. Clouds, snow and ice elements all display a similar spectral signature in both optical and thermal wavelengths. During the Antarctic night, both synthetic aperture radar (SAR) and infra-red images can monitor ice coverage, cloudy weather makes infra-red observation impossible. The scatterometer is an alternative instrument, but because of its low spatial resolution, it can only give rough estimations of large icebergs. Continuous monitoring of Antarctica can only be carried out by SAR imaging systems. This paper gives an example of Antarctic monitoring by analysing some elements of the drifting trajectory of the A-68A iceberg using Sentinel-1 SAR data

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