Investigation of Sea Ice Using Multiple Synthetic Aperture Radar Acquisitions

The papers of this thesis are not available in Munin. Paper I: Yitayew, T. G., Ferro-Famil, L., Eltoft, T. & Tebaldini, S. (2017). Tomographic imaging of fjord ice using a very high resolution ground-based SAR system. Available in IEEE Transactions on Geoscience and Remote Sensing, 55 (2):698-714. Paper II: Yitayew, T. G., Ferro-Famil, L., Eltoft, T. & Tebaldini, S. (2017). Lake and fjord ice imaging using a multifrequency ground-based tomographic SAR system. Available in IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 10(10):4457-4468. Paper III: Yitayew, T. G., Divine, D. V., Dierking, W., Eltoft, T., Ferro-Famil, L., Rosel, A. & Negrel, J. Validation of Sea ice Topographic Heights Derived from TanDEMX Interferometric SAR Data with Results from Laser Profiler and Photogrammetry. (Manuscript).The thesis investigates imaging in the vertical direction of different types of ice in the arctic using synthetic aperture radar (SAR) tomography and SAR interferometry. In the first part, the magnitude and the positions of the dominant scattering contributions within snow covered fjord and lake ice layers are effectively identified by using a very high resolution ground-based tomographic SAR system. Datasets collected at multiple frequencies and polarizations over two test sites in Tromsø area, northern Norway, are used for characterizing the three-dimensional response of snow and ice. The presented experimental results helped to improve our understanding of the interaction between radar waves and snow and ice layers. The reconstructed radar responses are also used for estimating the refractive indices and the vertical positions of the different sub-layers of snow and ice. The second part of the thesis deals with the retrieval of the surface topography of multi-year sea ice using SAR interferometry. Satellite acquisitions from TanDEM-X over the Svalbard area are used for analysis. The retrieved surface height is validated by using overlapping helicopter-based stereo camera and laser profiler measurements, and a very good agreement has been found. The work contributes to an improved understanding regarding the potential of SAR tomography for imaging the vertical scattering distribution of snow and ice layers, and for studying the influence of both sensor parameters such as its frequency and polarization and scene properties such as layer stratification, air bubbles and small-scale roughness of the interfaces on snow and ice backscattered signal. Moreover, the presented results reveal the potential of SAR interferometry for retrieving the surface topography of sea ice

Sea ice segmentation using Tandem-X pursuit mono static and alternative bistatic modes

Accepted manuscript version. Source at https://doi.org/10.1109/IGARSS.2017.8126964In this paper we investigate interferometric pairs of SAR images acquired by Tandem-X with the monostatic pursuit and the alternative bistatic modes for sea ice segmentation. The individual SAR images are modelled as non-Gaussian, and from the modelled data different features are extracted, stacked together and clustered. The interferometric coherence is regarded as an additional feature and utilized for clustering. In addition to complementing the information extracted from the individual images, the interferometric coherence is found to be capable of discriminating between open water and sea ice, as well as between different ice types

Investigation of Sea Ice Using Multiple Synthetic Aperture Radar Acquisitions

The thesis investigates imaging in the vertical direction of different types of ice in the arctic using synthetic aperture radar (SAR) tomography and SAR interferometry. In the first part, the magnitude and the positions of the dominant scattering contributions within snow covered fjord and lake ice layers are effectively identified by using a very high resolution ground-based tomographic SAR system. Datasets collected at multiple frequencies and polarizations over two test sites in Tromsø area, northern Norway, are used for characterizing the three-dimensional response of snow and ice. The presented experimental results helped to improve our understanding of the interaction between radar waves and snow and ice layers. The reconstructed radar responses are also used for estimating the refractive indices and the vertical positions of the different sub-layers of snow and ice. The second part of the thesis deals with the retrieval of the surface topography of multi-year sea ice using SAR interferometry. Satellite acquisitions from TanDEM-X over the Svalbard area are used for analysis. The retrieved surface height is validated by using overlapping helicopter-based stereo camera and laser profiler measurements, and a very good agreement has been found. The work contributes to an improved understanding regarding the potential of SAR tomography for imaging the vertical scattering distribution of snow and ice layers, and for studying the influence of both sensor parameters such as its frequency and polarization and scene properties such as layer stratification, air bubbles and small-scale roughness of the interfaces on snow and ice backscattered signal. Moreover, the presented results reveal the potential of SAR interferometry for retrieving the surface topography of sea ice

Multi-sensor data fusion and feature extraction for forest applications

The purpose of this study was to extract, evaluate and select different multi-frequency polarimetric SAR and multi-spectral optical features to demonstrate the benefit of multi-sensor data fusion for forest applications. Multi-frequency fully Polarimetric SAR data at P-, L- and C-band and multi-spectral Landsat TM data acquired over the Nezer forest in France were used for demonstration. The scene is composed of homogeneous fields of either bare soil or maritime pine trees of different ages, and the application was discriminating the bare soil, and the trees in terms of their ages. A total of twenty-six features; six from each of the three Polarimetric SAR datasets and eight from the optical dataset were extracted. Significant classification accuracy improvement (up to 12%) was achieved by fusing SAR and optical datasets. Therefore, attention should be given to the combined use of them whenever they are available. Five features were found to jointly preserve 98.5% of the classification information of the available set. In addition to retaining most of the valuable information, these few identified features were found useful to interpret the scene in terms of the different forest scattering mechanisms. Therefore, they can be reasonably expected to be used for other forest applications too

3-D imaging of sea ice using ground-based tomographic SAR data and comparison of the measurements with TerraSAR-X data

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Investigation of sea ice and lake ice using Ground-Based SAR tomography

International audienceIn this paper we present experimental results relative to the vertical structure of snow covered lake ice and sea ice, sensed with X-band radar system operated in a tomographic configuration. The available data are from a Ground-Based SAR campaign carried out over Prestvannet frozen lake and Kattfjord, both in Tromso, Norway. Direct imaging of the vertical structures of the snow and ice layers is achieved by focusing the signal from a 2D synthetic array in the 3D space. By making use of a priori information about the depth of snow and ice, the refractive index of snow and sea ice/lake ice is estimated from a single polarization tomographic measurement, and the results are in good agreement with previous experimental results. We have also shown that air bubbles in low salinity ice are the main contributors for the backscatter signal from ice

High Resolution Three-Dimensional Imaging of Sea Ice using Ground-Based Tomographic SAR Data

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Advanced Sentinel-1 Analysis Ready Data for Africa (ESA EO4SD: SAR-4-Africa), D5 – Final Report

Sentinel-1 (S1) of the European Copernicus Program provide consistent global cloud-independent synthetic aperture radar (SAR) imagery. However, there is a strong reluctance to use SAR data because of its complexity. Combined with the vast amount of data, S1 is out of reach for many stakeholders that could benefit from its monitoring potential. This project aims to overcome these technical challenges and subjective reluctance by providing attractive, easy-to-use “Advanced Sentinel-1 Analysis Ready Data” (ASARD) imagery. The main objective is to incite especially African users to include S1 data in their operations and thereby support the UN Sustainable Development Goals.publishedVersio

Lake and Fjord Ice Imaging Using a Multifrequency Ground-Based Tomographic SAR System

International audienceThe radar backscatter response of snow covered lake and fjord ice is investigated using a ground based multifrequency synthetic aperture radar system operated in a tomographic configuration. Direct imaging of the snow and ice layering is achieved by focusing the signal from a two-dimensional (2-D) synthetic array in the 3-D space. A mathematical derivation describing the propagation of electromagnetic waves across a dense and multilayered complex medium with arbitrary but finite number of layers is presented. It is used to estimate the depth and refractive indices of the snow and ice layers from the tomograms employing a simple least-square optimization scheme. The lake and fjord ice datasets are compared with respect to their vertical stratification and estimated refractive indices. The vertical structure of the reflectivity of the snow-covered lake ice is investigated and compared at two different frequencies, X-, and C-band. It is found that snow and ice volume responses at C-band are very low compared to the corresponding responses at X-band. At both frequencies, backscattering from surface and interface structures dominate volume contributions

Effects of Wave Propagation Velocity on X- And Ku-Band Tomographic Sar Imaging of Snowpack and Sea Ice

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