François Charbonneau

Characterization of target symmetric scattering using polarimetric SARs

Camerons coherent target decomposition (CTD) theory and the classification method that Cameron developed for operational use of his CTD are reconsidered. It is shown that Camerons classification leads to a coarse scattering segmentation because of the large class dispersion that corresponds to a synthetic aperture radar (SAR) system with about /spl plusmn/8-dB channel imbalance. The application of Camerons method within known SAR radiometric calibration requirements limits the utility of the classification. In addition, Camerons classification is applied under the implicit assumption on the coherence nature of target scattering, and this might yield erroneous results within areas of noncoherent scattering. A new method, named the symmetric scattering characterization method (SSCM), is introduced to better exploit the information provided by the largest target symmetric scattering component in the context of coherent scattering. The Poincare/spl acute/ sphere is used as the basis for a more complete representation of symmetric scattering than Camerons unit disk, thus enabling the SSCM to generate better segmentation of target symmetric scattering with much higher resolution. In order to limit the application of the SSCM to targets of coherent scattering, new methods are developed for assessment and validation of the coherent nature of point and extended target scattering.

Compact polarimetry overview and applications assessment

A synthetic aperture radar (SAR) with hybrid-polarity (CL-pol) architecture transmits circular polarization and receives two orthogonal, mutually coherent linear polarizations, which is one manifestation of compact polarimetry. The resulting radar is relatively simple to implement and has unique self-calibration features and low susceptibility to noise. It also enables maintenance of a larger swath coverage than fully polarimetric SAR systems. A research team composed of various departments of the Government of Canada evaluated this compact polarimetry mode configuration for application to soil moisture estimation, crop identification, ship detection, and sea-ice classification. This paper presents an overview of compact polarimetry, the approach developed for evaluation, and preliminary results for applications important to the Government of Canada. The implications of the results are also discussed with respect to future SAR missions such as the Canadian RADARSAT Constellation Mission, the American DESDynI, and India’s RISAT.

Ship detection and characterization using polarimetric SAR

Polarimetric information is investigated for ship detection and characterization at operational satellite synthetic aperture radar (SAR) incidence angles (20°‐60°). It is shown that among the conventional single-channel polarizations (HH, VV, or HV), HV provides the best ship‐sea contrast at incidence angles smaller than 50°. Furthermore, HH polarization permits the best ship‐sea contrast at near-grazing incidence angles. The wave polarization anisotropy is used for optimal information extraction from polarimetric SAR data. It is shown that fully polarimetric information permits a significant improvement in the ship‐sea contrast for relatively calm wind conditions, in comparison with conventional (i.e., scalar) single-channel polarizations (i.e., HH, VV, or HV). For rougher sea conditions, the effectiveness of polarimetric tools may be significantly degraded. Ship characterization is also investigated using the symmetric scattering characterization method (SSCM). Identification of ship targets with significant symmetric scattering can provide a useful ship pitch angle estimate under certain conditions.

Water resource applications with RADARSAT-2 – a preview

Abstract Fresh water is arguably the most vital resource for many aspects of a healthy and stable environment. Monitoring the extent of surface water enables resource managers to detect perturbations and long term trends in water availability, and set consumption guidelines accordingly. Potential end-users of water-related observations are numerous and reflect society as a whole. They encompass scientists and managers at all levels of government, aboriginal groups, water/power utility managers, farmers, planners, engineers, hydrologists, medical researchers, climate scientists, recreation enthusiasts, public school to post-graduate students, many special interest groups and the general public. Water data and analyses generate information products that benefit water resources planning and management, engineering design, plant operations, navigation activities, health research, water quality assessments and ecosystem management. As well, they serve as inputs for flood and drought warnings and weather and climate prediction models. Radar data in general, and RADARSAT in particular, are very good for detecting open surface water and have been used operationally for flood monitoring in many countries. Significant radar data archives now exist to analyse seasonal, annual and decadal trends, in order to attain a better understanding of the freshwater cycle. Radar data are also useful for wetland classification and soil moisture estimation. With the increasing pressure on water resources, both from a quality as well as a quantity perspective, the need will continue to increase for reliable information. RADARSAT-2 has several innovations that will enhance the ability to provide useful information about water resources. This paper provides an overview of the use of radar in general, and RADARSAT-2 in particular, for the generation of information products useful to water resource managers.

Compact polarimetry assessment for rice and wetland mapping

Polarimetric RADARSAT-2 data of rice and wetlands are used to simulate compact polarimetry (CP) mode data from the upcoming RADARSAT Constellation Mission (RCM). The simulated CP data are then used to evaluate the information content for rice and wetland mapping using supervised classification, and the results are compared for linear and circular polarization combinations and polarimetric decompositions from the fully polarimetric data and the simulated CP data. The results are consistent for both rice and wetlands and show that the classification accuracy increases as one goes up the polarization hierarchy. The circular polarizations produced the best classification results for the polarization combinations. This result requires further research to verify. Although the CP data did not perform as well as the fully polarimetric data, the results were better than for dual polarization, and this mode may offer the best option for rice and wetland mapping applications because of swath coverage. Note that both the compact simulations and the fully polarimetric data produced operationally suitable classification accuracies. Additional research is underway to evaluate the monitoring capability of this new CP mode. This article describes the approach used for the analyses and the classification results for both rice and wetlands.

Ship-sea contrast optimization when using polarimetric SARs

The polarization information was investigated in Touzi (2000) for ship detection using calibrated polarimetric Convair-580 SAR data that were collected within the incidence angle range of 45/spl deg/ to 70/spl deg/. It was shown that at operational satellite SAR incidence angles (lower than 60/spl deg/), there is a significant improvement of ship-sea contrast when the full polarimetric information is used instead of the information provided by the (scalar) one channel polarization (HH, VV, or HV). In this paper, the investigation is extended to lower incidence angles, and the robustness of the polarimetric discriminators used for ship enhancement, is assessed at various wind conditions (7, 14 and 20 knots). Polarization channel phase information is also investigated. It is shown that the information contained in the HH-VV channel phase difference, looks to be very promizing for ship enhancement, mainly when a dual-polarized SAR is used.

Characterization of symmetric scattering using polarimetric SARs

Camerons coherent target decomposition (CTD) and classification are discussed in the context of SAR, and the limitations of Camerons classification are examined. It is shown that these methods may lead to a coarse and misleading scattering segmentation because of the large radiometric dispersion tolerated in each of the elemental scatterer classes, as well as the implicit assumption on the coherence nature of target scattering. A new method, named the symmetric scattering characterization method (SSCM), is introduced to better exploit the information provided by the largest target symmetric scattering component, under coherent conditions. The SSCM, which expressed the symmetric scattering in term of the Poincare sphere angles, permits a better characterization of target symmetric scattering and the generation of coherent scattering segmentation of much higher resolution, in comparison with Camerons segmentation.

Quick Profiler (QuiP): a friendly tool to extract roughness statistical parameters using a needle profiler

QuiP is a graphical user interface (GUI) developed in MATLAB to extract and analyze soil surface profile measurements obtained from a needle profiler in a few minutes. Surface roughness parameters can be extracted from any needle profiler with simple modifications to the tool. QuiP calculates many statistics useful in radar remote sensing while generating the profiles. Furthermore, a QuiP function can be used to join several profiles. Long profiles can therefore be created from a short profiler (e.g., 1 m) that is easier to carry and handle in the field. Extraction of profiles by QuiP is repeatable and therefore reduces user’s errors from data processing.

Change Detection with Compact Polarimetric SAR for Monitoring Wetlands

Abstract. Compact polarimetric synthetic aperture radar (SAR) architecture is an SAR configuration that consists of transmitting a single circular polarization (left or right) or a 45° oriented linear signal while receiving two linear polarizations, horizontal and vertical. In this study we investigate the potential of the compact polarimetric SAR mode for wetland monitoring applications. Whitewater Lake located in Manitoba, Canada, is selected as a case study where simulated compact polarimetric SAR data are obtained using RADARSAT-2 Fine Quad-POL SAR images. The ability of the compact polarimetric data to monitor wetlands using the Wishart-Chernoff distance is studied and compared to the results obtained using fully polarimetric data. Results of this study show that compact polarimetry provides monitoring capabilities for wetlands. Promising change detection mapping results based on the compact polarimetric coherency matrices are obtained using the Wishart-Chernoff distance. This could be useful for flagging change in the wetland environment for further evaluation and action if required. The compact polarimetry mode could be an attractive configuration for future SAR systems due to the combination of swath coverage, moderate resolution, and enhanced information content for monitoring changes in surface water and flooded vegetation. Résumé. L’architecture du radar à synthèse d’ouverture (SAR) en polarimétrie compacte est une configuration SAR qui transmet un seul signal en polarisation circulaire (gauche ou droite) ou un signal linéaire à 45 degrés tout en recevant deux polarisations linéaires, horizontales et verticales. Dans cette étude, nous étudions le potentiel du mode en polarimétrie compacte du SAR pour les applications de surveillance des zones humides. Le lac Whitewater, situé au Manitoba, au Canada, est sélectionné pour une étude de cas où les données SAR en polarimétrie compacte simulées sont obtenues en utilisant les images SAR en mode quad-pol fin du RADARSAT-2. La capacité des données en polarimétrie compacte pour surveiller les zones humides à l’aide de la distance Wishart-Chernoff a été étudiée, puis comparée aux résultats obtenus en utilisant les données en polarimétrie complète. Les résultats de cette étude montrent que la polarimétrie compacte offre des capacités de surveillance pour les zones humides. Des résultats prometteurs de la cartographie de détection du changement basée sur les matrices de cohérence de la polarimétrie compacte ont été obtenus en utilisant la distance Wishart-Chernoff. Ceci pourrait être utile pour signaler les changements dans les zones humides pour une évaluation supplémentaire et une action le cas échéant. Le mode en polarimétrie compacte pourrait être une configuration attrayante pour les futurs systèmes SAR en raison de la combinaison de la largeur de la couverture au sol, de la résolution moyenne et du contenu d’information effective pour la surveillance des changements dans les eaux de surface et la végétation inondée.

Using RADARSAT-2 polarimetric and ENVISAT-ASAR dual-polarization data for estimating soil moisture over agricultural fields

There are several challenges in estimating soil moisture from radar remote sensing over agricultural fields in eastern Canada. To begin, snow cover or frozen ground is observed from November to April. From April to May, agricultural activities (e.g., ploughing and sowing) change the surface roughness from week to week thereby limiting the applicability of multitemporal and multi-incidence angle approaches. Techniques using a priori information on surface roughness are difficult to apply since the type of crop often changes from year to year. Here, we present an approach using effective roughness parameters (i.e., effective root mean square height and effective correlation length) that are obtained using an empirical relationship (independent of the crop type) between the root mean square height and the correlation length. The effective parameters allow us to resolve the Integral Equation Model for observed incidence angle and backscattering coefficient in HH and VV polarizations (σ°HH and σ°VV) using a look-up table. An additional challenge is posed by the growth of vegetation that begins in May. Three-component decompositions and radar vegetation indices were used to characterize the vegetation in agricultural fields. Surface backscattering coefficients in HH and VV polarizations (σ°SURF_HH and σ°SURF_VV) were calculated using the decompositions. An improvement in estimates of soil moisture was observed with the use of surface backscattering coefficients for bare soil and sparsely vegetated fields instead of the total backscattering.