AEL Consultants

Cupar, United Kingdom

AEL Consultants

Cupar, United Kingdom
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Chen H.,Natural Resources Canada | Cloude S.R.,AEL Consultants | Goodenough D.G.,University of Victoria
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2016

In this paper, we report results of a study aimed at assessing the potential for using X-band single-pass radar interferometric coherence for forest canopy height estimation. We use datasets from the Tandem-X satellite pair collected over Canadian forest test sites, where supporting lidar data are available for validation. We first employ dual-copolarized modes to assess the potential of polarimetric interferometry for forest canopy height retrieval. We show that for this forest type, single polarization modes have better properties, including much improved spatial coverage. We develop a new algorithm for single polarization data and validate the canopy height products against lidar. We then extend the canopy height product over a mosaic of multiple swaths to demonstrate the potential for very wide area forest height mapping using radar coherence. © 2008-2012 IEEE.


Marino A.,ETH Zurich | Cloude S.R.,AEL Consultants | Lopez-Sanchez J.M.,University of Alicante
IEEE Transactions on Geoscience and Remote Sensing | Year: 2013

In modern society, the anthropogenic influences on ecosystems are central points to understand the evolution of our planet. A polarimetric synthetic aperture radar may have a significant contribution in tackling problems concerning land use change, since such data are available with any-weather conditions. Additionally, the discrimination capability can be enhanced by the polarimetric analysis. Recently, an algorithm able to identify targets scattering an electromagnetic wave with any degree of polarization has been developed, which makes use of a vector rearrangement of the elements of the coherency matrix. In the present work, this target detector is modified to perform change detection between two polarimetric acquisitions, for land use monitoring purposes. Regarding the selection of the detector parameters, a physical rationale is followed, developing a new parameterization of the algebraic space where the detector is defined. As it will be illustrated in the following, this space is 6-D complex with restrictions due to the physical feasibility of the vectors. Specifically, a link between the detector parameters and the angle differences of the eigenvector model is obtained. Moreover, a dual polarimetric version of the change detector is developed, in case quad-polarimetric data are not available. With the purpose of testing the methodology, a variety of data sets were exploited: quadpolarimetric airborne data at L-band (E-SAR), quad-polarimetric satellite data at C-band (Radarsat-2), and dual-polarimetric satellite data at X-band (TerraSAR-X). The algorithm results show agreement with the available information about land changes. Moreover, a comparison with a known change detector based on the maximum likelihood ratio is presented, providing improvements in some conditions. The two methodologies differ in the analysis of the total amplitude of the backscattering, where the proposed algorithm does not take this into consideration. © 2012 IEEE.


Cloude S.R.,AEL Consultants | Goodenough D.G.,Natural Resources Canada | Chen H.,Natural Resources Canada
IEEE Geoscience and Remote Sensing Letters | Year: 2012

In this letter, we develop several new aspects of target decomposition theory for use with compact-mode polarimetric radar data. We first make a general link between fully polarimetric systems and compact modes before developing two important types of decomposition, namely, entropy/alpha and model-based surface/dihedral/volume techniques. We show that, under certain assumptions, compact data can be used to estimate the rotation invariant alpha angle of quadpol systems, which can then be used for polarimetric classification and physical parameter estimation. We apply the new methods to the problem of historical forest fire scar detection, using data at L- and C-bands to demonstrate the preservation of signatures in transition from quad to compact modes. © 2011 IEEE.


Lopez-Sanchez J.M.,University of Alicante | Vicente-Guijalba F.,University of Alicante | Ballester-Berman J.D.,University of Alicante | Cloude S.R.,AEL Consultants
IEEE Geoscience and Remote Sensing Letters | Year: 2015

The coherent nature of the acquisition by TerraSAR-X of both copolar channels (HH and VV) enables the generation of many different polarimetric observables with physical interpretation, as have recently been used for monitoring rice fields. In this letter, the influence of incidence angle upon these polarimetric observables is analyzed by comparing three stacks of images that were acquired simultaneously at different incidence angles (22 ^{\circ}, 30 ^{\circ}, and 40 ^{\circ}) during a whole cultivation campaign. We show that the response of observables related to dominance (entropy, ratios of components) and type of scattering mechanisms (alpha angles) is not greatly influenced by incidence angle at some stages: early and advanced vegetative phases, and maturation. Moreover, the acquisition geometry drives the sensitivity to the presence of the initial stems and tillers, being detected earlier at shallower angles. This analysis is a necessary step before studying potential methodologies for combining different orbits and beams for reducing the time between acquisitions for monitoring purposes. © 2004-2012 IEEE.


Lopez-Sanchez J.M.,University of Alicante | Ballester-Berman J.D.,University of Alicante | Cloude S.R.,AEL Consultants
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2011

This work presents a study about the evolution of the radar response of rice fields at X-band as a function of their phenology, by using three time series of coherent HHVV dual-pol X-band radar images acquired by the TerraSAR-X sensor at different incidence angles during a whole cultivation season. After analyzing a wide set of polarimetric observables, with particular sensitivities at different moments along the campaign, an approach to retrieve the phenological stage with a single acquisition is proposed and tested. © 2011 IEEE.


Lopez-Sanchez J.M.,University of Alicante | Cloude S.R.,AEL Consultants | Ballester-Berman J.D.,University of Alicante
IEEE Transactions on Geoscience and Remote Sensing | Year: 2012

The feasibility of retrieving the phenological stage of rice fields at a particular date by employing coherent copolar dual-pol X-band radar images acquired by the TerraSAR-X sensor has been investigated in this paper. A set of polarimetric observables that can be derived from this data type has been studied by using a time series of images gathered during the whole cultivation period of rice. Among the analyzed parameters, besides backscattering coefficients and ratios, we have observed clear signatures in the correlation (in magnitude and phase) between channels in both the linear and Pauli bases, as well as in parameters provided by target decomposition techniques, like entropy and alpha from the eigenvector decomposition. A new model-based decomposition providing estimates of a random volume component plus a polarized contribution has been proposed and employed in interpreting the radar response of rice. By exploiting the signatures of these observables in terms of the phenology of rice, a simple approach to estimate the phenological stage from a single pass has been devised. This approach has been tested with the available data acquired over a site in Spain, where rice is cultivated, ensuring ground is flooded for the whole cultivation cycle, and sowing is carried out by randomly spreading the seeds on the flooded ground. Results are in good agreement with the available ground measurements despite some limitations that exist due to the reduced swath coverage of the dual-pol HHVV mode and the high noise floor of the TerraSAR-X system. © 2011 IEEE.


Lopez-Sanchez J.M.,University of Alicante | Vicente-Guijalba F.,University of Alicante | Ballester-Berman J.D.,University of Alicante | Cloude S.R.,AEL Consultants
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2015

Dual-pol HHVV images acquired by TerraSAR-X/TanDEM-X during 4 years, with 3 different incidence angles, over rice fields in Spain are analysed and employed to retrieve the phe-nological state of rice crops in a scale of 3 to 5 possible intervals. A decision tree approach is employed for the retrieval algorithm. Results show that the joint processing of all angles provides a good performance, only 2-4% worse than a separate processing. The role of polarimetry is demonstrated by obtaining a total accuracy of 88.6% when coherent dual-pol data are considered, instead of 75.6% for incoherent dual-pol. © 2015 IEEE.


Marino A.,University of Edinburgh | Cloude S.R.,AEL Consultants | Woodhouse I.H.,University of Edinburgh
IEEE Transactions on Geoscience and Remote Sensing | Year: 2010

The contribution of synthetic aperture radar polarimetry in target detection is described and found to add valuable information. A new target detection methodology that makes novel use of the polarization fork of the target is described. The detector is based on a correlation procedure in the target space, and other target representations (e.g., Huynen parameters or α angle) can be employed. The mathematical formulation is general and can be applied to any kind of single target; however, in this paper, the detection is optimized for the odd and even bounces (the first two elements of the Pauli scattering vector) and for the oriented dipoles. Validation against real data shows significant agreement with the expected results based on the theoretical description. © 2010 IEEE.


Cloude S.R.,AEL Consultants
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2013

In this paper, we consider the forward problem in depolarization by optical systems. That is, we seek a compact parameterization that allows us to take an arbitrary "pure" optical system (namely one defined by a single Mueller-Jones matrix) and model all possible ways in which that system can depolarize light. We model this structure using compound unitary transformations and illustrate physical interpretation of the parameters involved by considering four examples, the family of depolarizers generated by scattering by random nonspherical particle clouds. We then turn attention to circular polarizers before considering all ways in which mirror reflection can cause depolarization. Finally, we consider a numerical example applied to a published Mueller matrix for backscatter from chiral turbid media. © 2013 Optical Society of America.


Cloude S.R.,AEL Consultants
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2011

In this paper we provide a review of developments in the field of polarimetric SAR interferometry or POLInSAR, beginning with its origins in data from the SIR-C mission in 1994 and culminating in its latest application to Tandem-X, a space-borne single pass X-Band interferometer launched in 2010. Linking these two important developments in technology we trace the parallel development of signal processing, coherent scattering models and bio-geophysical parameter estimation that have led us to our present understanding of the potential of this new technology for remote sensing applications. © 2011 IEEE.

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