Resumo: O propósito deste trabalho foi avaliar o potencial dos dados PALSAR polarimétricos para discriminar e mapear espécies de macrófitas (vegetação aquática) de uma área alagável da Amazônia, a planície de inundação do Lago Grande de Monte Alegre, no estado do Pará. A coleta de dados foi realizada quase simultaneamente à aquisição dos dados de radar. Três principais espécies de macrófitas foram encontradas na área: Paspalum repens (PR), Hymenachne amplexicaulis (HA) e Paspalum elephantipes (PE). Variáveis morfológicas foram medidas em campo e usadas para derivar outras variáveis tais como a biomassa. Atributos foram gerados a partir da matriz de covariância [C] extraída da imagem ALOS/PALSAR em modo SLC (single look complex). Os atributos polarimétricos foram analisados para as três espécies e identificados aqueles capazes de discriminar as espécies. Foram aplicadas as seguintes abordagens de classificação: baseada em regras, baseada em modelos de decomposição (Decomposições de Freeman-Durden e Cloude-Pottier), baseada em estatística (Classificação supervisionada baseada na distância Wishart) e híbrida (Classificador Wishart com classes de entrada baseadas na decomposição de Cloude-Pottier). Finalmente, a variável morfológica "volume da haste" foi modelada por regressão múltipla em função de alguns atributos polarimétricos. Os resultados sugerem que a imagem polarimétrica banda L possui potencial para discriminar as espécies de macrófitas, sendo os principais atributos para isso sigma zero HH ( ), sigma zero HV ( ) e sigma zero VV ( ), índice de estrutura da copa ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The purpose of this work was to evaluate the potential of fully polarimetric PALSAR data to discriminate and map macrophyte species in the Amazon floodplain, more specifically in the Monte Alegre Lake, in the state of Pará, Brazil. Fieldwork was carried out almost simultaneously to the radar acquisition. Three main species were found in the study area: Paspalum repens (PR), Hymenachne amplexicaulis (HA) and Paspalum elephantipes (PE). Macrophyte morphological variables were measured on the field and used to derive others variables, like the biomass. Attributes were calculated from the covariance matrix [C] derived from the SLC (single look complex) data. The polarimetric attributes were analyzed for the three species and it was identified that ones capable of discriminating them. The following classification approaches were applied: a rule-based classification, model-based classifications (Freeman-Durden and Cloude-Pottier), a statistical-based classification (supervised classification using Wishart distance measure) and a hybrid classification (Wishart classifier with the input classes based on the H/a plane). Finally, the morphological variable "stem volume" was modeled using multiple regression. The findings suggest that the fully polarimetric image has potential for discriminating plant species, being the main attributes sigma-nought HH ( ), sigma-nought HV ( ) and sigma-nought VV ( ), canopy structure index ( ), HH-VV polarimetric coherence ( ), helicity of the third scattering mechanism (τ ), orientation angle of the first scattering mechanism ( ) and scattering type phase of the first mechanism ( ); among the different classifications, only the supervised (Wishart) and the rule-based discriminated the species, with overall accuracy of 75,04% and 87,18%, respectively; the stem volume was modeled using the following attributes: biomass index ( ), volumetric scattering ... (Complete abstract click electronic access below) / Orientador: Nilton Nobuhiro Imai / Coorientador: José Cláudio Mura / Banca: Evlyn Marcia Leão de Moraes Novo / Banca: Thiago Sanna Freire Silva / Banca: João Roberto dos Santos / Banca: Vilma Mayumi Tachibana / Doutor

Diese (Doktor)arbeit beschäftigt sich mit Radar-Polarimetrie, insbesondere mit der Untersuchung der Eigenschaften von polarimetrischen Variablen, die potenziellen Nutzen für die Radar-Meteorologie haben. Für den Einsatz in Dual-Polarisations-Radargeräten wird der Polarisationsgrad analysiert. Diese Variable wird in künftigen operationellen Radargeräten verfügbar sein. Der Polarisationsgrad hängt vom transmittierten Polarisationszustand und in weiterer Folge auch vom Betriebsmodus des Radargeräts ab. Der Hauptbetriebsmodus von operationellen Radargeräten sendet und empfängt gleichzeitig sowohl die horizontale als auch die vertikale Komponente. Der sekundäre Betriebsmodus sendet und empfängt simultan die horizontal polarisierte Komponente. In dieser Arbeit werden beide Polarisationsgrade untersucht. Da operationelle Systeme derzeit auf den Dual-Polarisationsmodus aufgerüstet werden, sollte künftig die Anwendungsmöglichkeiten von vollpolarimetrischen Wetterradarsystemen untersucht werden. Aus allen Variablen, die in diesem Betriebsmodus zur Verfügung stehen, wurde die Entropie (des gemessen Objektes) ausgewählt und wegen seiner engen Beziehung zum Polarisationsgrad näher untersucht. / The present doctoral thesis deals with radar polarimetry, namely with the investigation of properties of polarimetric variables potentially useful in radar meteorology. For use with dual-polarization radars, the degree of polarization is analyzed. This variable is available to planned operational radars. The degree of polarization is dependent on transmit polarization state and, consequently, it is dependent on the radar system operating mode. The primary operating mode of operational radars consists in simultaneous transmission and simultaneous receive of both horizontal and vertical components. The secondary operating mode consists of horizontal transmission and simultaneous receive. Both degrees of polarization are investigated in this thesis. Also, as operational systems are being updated to dual-polarization, research should start investigating the capabilities of fully polarimetric weather radar systems. Among the numerous variables available from this operating mode, the target entropy was chosen for investigation, also because of its close relation to the degree of polarization

In this study a calibration concept for a multi-polarimetric weather radar is developed. Several common calibration techniques are analysed, but many are insufficient due to the non-reciprocal behaviour of the employed radar. Hence, an electronic calibration device was developed, which was designed for fast polarization determination of any polarization (including elliptical ones). The non-reciprocal behaviour was overcome by splitting receive and transmit calibration, which virtually uses the radar as a communication system. Beside the calibration a new and exible signal processing system was implemented on that radar which allows interleaved measurements using several polarimetric modes. This capability was used to analyse the STAR (hybrid basis with linear 45° transmit and horizontal/vertical receive) mode and the alternating H/V mode with respect to depolarization. Although it is known that depolarization causes errors in STAR mode, it is used in most commercial weather radars. / In dieser Arbeit wird ein Kalibrierkonzept für ein Multipolarisation-Radar entwickelt. Dazu wurden verschiedene gebräuchliche Techniken untersucht. Dabei stellte sich heraus, dass dieses Verfahren für das untersuchte nichtreziproke Radar unzureichend sind. Deshalb wurde ein elektronisches Kalibriergerät entwickelt, welches speziell der schnellen Messung von beliebigen Polarisationen - einschließlich Elliptischer - dient. Das nichtreziproke Verhalten wurde durch die Aufteilung in eine Sende- und eine Empfangskalibrierung umgangen, wodurch das Radar praktisch als Kommunikationssystem verwendet wird. Des Weiteren wurde eine neue, fexible Signalverarbeitung an dem Radar entwickelt, welches gemischte Messungen mit mehreren Polarisationsmoden erlaubt. Diese neuartige Möglichkeit wurde benutzt um den STAR-Modus, welches eine hybride Polarisationsbasis (linear 45° senden, horizontal/vertikal empfangen) benutzt, mit dem alternierende H/V-Modus zu vergleichen. Dabei wurde speziell das Verhalten des STAR-Modus im Hinblick auf Depolarisation untersucht, da dies bekanntermaßen zu Fehlern in den Messgrößenführen kann. Dies ist von besonderem Interesse, da der STAR-Modus in den meisten kommerziellen Wetterradarsystemen eingesetzt wird.

Im Rahmen dieser Studie wurden Beobachtungen eines bodengebundenen, scannenden, polarimetrischen Wolken-Doppler-Radars genutzt, um Vertikalprofile der Form und Ausrichtung von bis zu 5 Hydrometeor-Typen in Mischphasenwolken abzuleiten. Voraussetzung für die neue Methodik war ein bestehender Ansatz, der Elevationsscans (Range-Height-Indikator, RHI) der differentiellen Reflektivität ZDR und des Korrelationskoeffizienten RHV nutzt, die von einem 35-GHz (Ka-Band) Wolken-Doppler-Radar beobachtet wurden. ZDR und RHV am Ort des maximalen Signals in den beobachteten Dopplerspektren werden anschließend mit entsprechenden simulierten Elevationsabhängigkeiten von ZDR und RHV verglichen. Das Ergebnis des Retrievals, das mittels eines Fits der simulierten und beobachteten ZDR und RHV Werte erhalten wird, ist ein Paar des polarizability ratio (dichtegewichtetes Achsenverhältnis) und dem degree of orientation, einem Maß für die bevorzugte Ausrichtung der Teilchen. Diese Arbeit widmet sich der Erweiterung der ursprünglichen Ansatzes der Form- und Ausrichtungsbestimmung. Die Methode nutzt die vollständigen beobachteten Dopplerspektren von ZDR und RHV für alle Elevationswinkel der vom 35-GHz Wolkenradar durchgeführten RHI-Scans. Die Aufteilung der Doppler-Spektren in 5 Teile ermöglicht die Ermittlung von Vertikalprofilen der Hydrometeor-Verteilung. In dieser Arbeit wird zunächst der ursprüngliche Ansatz zur Bestimmung der Form und Ausrichtung von Hydrometeors rekapituliert. Anschließend werden das Splitting-Verfahren und die Schritte der Datenanalysekette vorgestellt. Insbesondere auf die Korrektur von Horizontalwindeffekten auf die Doppler-Spektren wird eingegangen. Die Anwendbarkeit des neuen, erweiterten Ansatzes wird anhand von vier Fallstudien demonstriert. Ein Fall diskutiert die Identifizierung von Variationen der Form- und Ausrichtung innerhalb einer Hydrometeor-Population, die vollständig der gleichen primären Form-klasse angehört. Zwei Fallstudien zeigen die Anwendung des Algorithmus in Umgebungen mit mehreren Hydrometeortypen, einschließlich der Identifizierung von sekundärer Eisbildung. In der vierten Fallstudie wurde der Einfluss der Kristallmorphologie und -orientierung auf die Lichtstreuung in einer Mischphasenwolke charakterisiert. Die spektral aufgelöste Form- und Orientierungsbestimmung zeigt, dass vertikal ausgedehnte Mischphasenwolken praktisch immer eine Mischung verschiedener Hydrometeorarten oder eine beträchtliche Variation einer einzigen Hydrometeorart enthalten. Diese Information ist insofern von Bedeutung, als dass viele bestehende Fernerkundungsdaten auf der Annahme beruhen, dass nur eine einzige Hydrometeor-Population vorhanden ist.:1 Introduction 2 Introduction to mixed-phase clouds and ice crystals 2.1 Introduction to mixed–phase clouds 2.2 Ice formation 2.3 Morphology of ice crystals 2.4 Ice crystal growth and secondary ice formation processes 2.4.1 Riming: interaction between supercooled liquid droplets and ice crystals 2.4.2 Aggregation: interaction between ice crystals 2.4.3 Secondary ice production 2.5 Relation between fall speed and shape of ice particles 3 Simulating backscattering by hydrometeors in the microwave regime 3.1 Overview of scattering approaches 3.2 Spheroidal scattering approach 4 Radar observations of atmospheric hydrometeors 4.1 Polarimetric cloud radars 4.1.1 Radar reflectivity 4.1.2 Differential reflectivity 4.1.3 Correlation coefficient 4.1.4 Linear depolarization ratio 4.1.5 Doppler capability 4.2 Retrieving hydrometeor shape and orientation 4.2.1 Modeling part 4.2.2 Observational part 4.2.3 Comparing modeling and observational parts 5 Instrumentation and Dataset 5.1 Hybrid-mode cloud radar Mira-35 5.2 ACCEPT campaign 5.3 Retrieval of shape and orientation of the main hydrometeor population from STSR cloud radar observations 5.3.1 Toward extension of the main-peak approach 6 Doppler-spectra separation method for retrieving shape and orientation of multiple hydrometeor populations 6.1 Spectrally resolved approach 6.2 The influence of air motion on the Doppler spectra observed by a scanning cloud radar 6.2.1 Retrieval of horizontal wind from PPI scans 6.2.2 Aliasing problem and Doppler shift correction 6.2.3 An illustrative example showcasing the correction of horizontal wind effects 6.3 Application of spectrally resolved approach on the case study from 07 Nov 2014, 09:15 – 09:30UTC 7 Results: Application of the spectrally resolved approach on Analysis of the Composition of Cloud with Extended Polarization Techniques (ACCEPT) data 7.1 Case study 10 Nov 2014, 01:15 – 01:30: Shape variability within a deep mixed-phase cloud 7.2 Case study 03 Nov 2014, 20:30 – 20:45: Secondary ice formation 7.3 Case study 18 Nov 2014, 01:15 – 01:30: Impact of crystal morphology on light scattering in a mixed-phase cloud 7.3.1 Relationship between lidar depolarization ratio and ice crystal morphology 7.3.2 Investigation of particle shape and orientation of a low-depolarization cloud layer 8 Summary & Conclusion List of Abbreviations and Acronyms List of Symbols Bibliography / In the framework of this study ground-based scanning polarimetric cloud Doppler radar observations were utilized to derive vertical profiles of the shape and orientation of up to 5 different hydrometeor types in mixed-phase clouds. Prerequisite for the new methodology was an existing approach that uses elevation (range-height indicator, RHI) scans of differential reflectivity ZDR and correlation coefficient RHV observed by a 35-GHz (Ka-band) cloud Doppler radar as well as simulations of the latter. ZDR and RHV from the location of the maximum signal in the observed Doppler spectra are compared with corresponding simulated elevation dependencies of ZDR and RHV. The retrieval output, which is obtained by a fit of simulated and observed ZDR and RHV, is then a pair of the polarizability ratio (density-weighted axis ratio) and the degree of orientation, a measure of the preferable orientation of the particles. This thesis is dedicated to an extension of the original shape and orientation retrieval. The method utilizes the entire observed Doppler spectra of ZDR and RHV from all elevation angles of the RHI scans performed by the 35-GHz cloud radar. The split- up of the Doppler spectra into 5 parts enables the retrieval of vertical profiles of the hydrometeor distribution. Within the thesis, the original shape retrieval approach is recapitulated. Subsequently, the splitting procedure and required preparatory steps in the data analysis chain are introduced. Specifically, a correction of horizontal wind effects on the Doppler spectra had to be implemented. The remainder of the thesis is dedicated to demonstrate the applicability of the new spectrally shape and orientation retrieval approach by means of four case studies. One case demonstrates the detection of variabilities in shape and orientation within a hydrometeor population belonging entirely to the same primary shape class. Two case studies were selected to evaluate the application of the spectrally resolved approach in an environment of multiple hydrometeor types, including its utilization for identification of secondary ice production. In the fourth case study the characterization of the impact of crystal morphology and orientation on light scattering in a mixed-phase cloud was performed. The spectrally resolved shape and orientation retrieval demonstrates that vertically extensive mixed-phase clouds contain virtually always a mix of different hydrometeor types or a considerable variation of a single hydrometeor type. This information holds relevant as many existing remote sensing retrievals rely on the assumption of the presence of a single hydrometeor population, only.:1 Introduction 2 Introduction to mixed-phase clouds and ice crystals 2.1 Introduction to mixed–phase clouds 2.2 Ice formation 2.3 Morphology of ice crystals 2.4 Ice crystal growth and secondary ice formation processes 2.4.1 Riming: interaction between supercooled liquid droplets and ice crystals 2.4.2 Aggregation: interaction between ice crystals 2.4.3 Secondary ice production 2.5 Relation between fall speed and shape of ice particles 3 Simulating backscattering by hydrometeors in the microwave regime 3.1 Overview of scattering approaches 3.2 Spheroidal scattering approach 4 Radar observations of atmospheric hydrometeors 4.1 Polarimetric cloud radars 4.1.1 Radar reflectivity 4.1.2 Differential reflectivity 4.1.3 Correlation coefficient 4.1.4 Linear depolarization ratio 4.1.5 Doppler capability 4.2 Retrieving hydrometeor shape and orientation 4.2.1 Modeling part 4.2.2 Observational part 4.2.3 Comparing modeling and observational parts 5 Instrumentation and Dataset 5.1 Hybrid-mode cloud radar Mira-35 5.2 ACCEPT campaign 5.3 Retrieval of shape and orientation of the main hydrometeor population from STSR cloud radar observations 5.3.1 Toward extension of the main-peak approach 6 Doppler-spectra separation method for retrieving shape and orientation of multiple hydrometeor populations 6.1 Spectrally resolved approach 6.2 The influence of air motion on the Doppler spectra observed by a scanning cloud radar 6.2.1 Retrieval of horizontal wind from PPI scans 6.2.2 Aliasing problem and Doppler shift correction 6.2.3 An illustrative example showcasing the correction of horizontal wind effects 6.3 Application of spectrally resolved approach on the case study from 07 Nov 2014, 09:15 – 09:30UTC 7 Results: Application of the spectrally resolved approach on Analysis of the Composition of Cloud with Extended Polarization Techniques (ACCEPT) data 7.1 Case study 10 Nov 2014, 01:15 – 01:30: Shape variability within a deep mixed-phase cloud 7.2 Case study 03 Nov 2014, 20:30 – 20:45: Secondary ice formation 7.3 Case study 18 Nov 2014, 01:15 – 01:30: Impact of crystal morphology on light scattering in a mixed-phase cloud 7.3.1 Relationship between lidar depolarization ratio and ice crystal morphology 7.3.2 Investigation of particle shape and orientation of a low-depolarization cloud layer 8 Summary & Conclusion List of Abbreviations and Acronyms List of Symbols Bibliography

Aim of PhD research is to exploit SAR Polarimetry technique for the identification of surface and subsurface archaeological features in the site of Gebel Barkal (Sudan), inscribed in the UNESCO World Heritage List since 2003. Sand penetration capability of both C-band and L-band sensors are discussed analysing archived ALOS PALSAR and RADARSAT-2 specifically acquired (2012-2013) images. Moreover, the research activity illustrates the potential of integrating SAR polarimetric and optical satellite data in a dedicated GIS project, realised in collaboration with the Universities of Turin and Venice (Italy). The monitoring of ancient sites by means of remotely acquired polarimetric SAR data represents a benefit for the archaeological research, where detected anomalies can address archaeological excavations or ground truth verification, as shown in the PhD dissertation, and where threatening factors affect the integrity of a cultural site.

This work has as goal to study the microwaves behavior over the archaeological structures still visible in the historical city of Samarra, the capital of the ancient Abbasid Caliphate located in Iraq. Three areas were taken into account for the Ph.D. research: an octagonal city, three racecourses stadiums and the city of al-Mutawakkiliyya. Threats to which the site is exposed and its historical importance let the city to be inscribed in the list of UNESCO sites in danger (2007). This gave a reason more to investigate this area by means of SAR RADARSAT-2 and ALOS PALSAR satellites. SAR potentiality, in fact, is well known, in particular for those areas of the World where surveys in situ are not allowed because of political instability (as in the case of Samarra) and because of the possibility of acquiring with any cloud cover conditions and in any kind of illumination (day/night).

Les milieux humides remplissent plusieurs fonctions écologiques d’importance et contribuent à la biodiversité de la faune et de la flore. Même s’il existe une reconnaissance croissante sur l’importante de protéger ces milieux, il n’en demeure pas moins que leur intégrité est encore menacée par la pression des activités humaines. L’inventaire et le suivi systématique des milieux humides constituent une nécessité et la télédétection est le seul moyen réaliste d’atteindre ce but. L’objectif de cette thèse consiste à contribuer et à améliorer la caractérisation des milieux humides en utilisant des données satellites acquises par des radars polarimétriques en bande L (ALOS-PALSAR) et C (RADARSAT-2). Cette thèse se fonde sur deux hypothèses (chap. 1). La première hypothèse stipule que les classes de physionomies végétales, basées sur la structure des végétaux, sont plus appropriées que les classes d’espèces végétales car mieux adaptées au contenu informationnel des images radar polarimétriques. La seconde hypothèse stipule que les algorithmes de décompositions polarimétriques permettent une extraction optimale de l’information polarimétrique comparativement à une approche multipolarisée basée sur les canaux de polarisation HH, HV et VV (chap. 3). En particulier, l’apport de la décomposition incohérente de Touzi pour l’inventaire et le suivi de milieux humides est examiné en détail. Cette décomposition permet de caractériser le type de diffusion, la phase, l’orientation, la symétrie, le degré de polarisation et la puissance rétrodiffusée d’une cible à l’aide d’une série de paramètres extraits d’une analyse des vecteurs et des valeurs propres de la matrice de cohérence. La région du lac Saint-Pierre a été sélectionnée comme site d’étude étant donné la grande diversité de ses milieux humides qui y couvrent plus de 20 000 ha. L’un des défis posés par cette thèse consiste au fait qu’il n’existe pas de système standard énumérant l’ensemble possible des classes physionomiques ni d’indications précises quant à leurs caractéristiques et dimensions. Une grande attention a donc été portée à la création de ces classes par recoupement de sources de données diverses et plus de 50 espèces végétales ont été regroupées en 9 classes physionomiques (chap. 7, 8 et 9). Plusieurs analyses sont proposées pour valider les hypothèses de cette thèse (chap. 9). Des analyses de sensibilité par diffusiogramme sont utilisées pour étudier les caractéristiques et la dispersion des physionomies végétales dans différents espaces constitués de paramètres polarimétriques ou canaux de polarisation (chap. 10 et 12). Des séries temporelles d’images RADARSAT-2 sont utilisées pour approfondir la compréhension de l’évolution saisonnière des physionomies végétales (chap. 12). L’algorithme de la divergence transformée est utilisé pour quantifier la séparabilité entre les classes physionomiques et pour identifier le ou les paramètres ayant le plus contribué(s) à leur séparabilité (chap. 11 et 13). Des classifications sont aussi proposées et les résultats comparés à une carte existante des milieux humide du lac Saint-Pierre (14). Finalement, une analyse du potentiel des paramètres polarimétrique en bande C et L est proposé pour le suivi de l’hydrologie des tourbières (chap. 15 et 16). Les analyses de sensibilité montrent que les paramètres de la 1re composante, relatifs à la portion dominante (polarisée) du signal, sont suffisants pour une caractérisation générale des physionomies végétales. Les paramètres des 2e et 3e composantes sont cependant nécessaires pour obtenir de meilleures séparabilités entre les classes (chap. 11 et 13) et une meilleure discrimination entre milieux humides et milieux secs (chap. 14). Cette thèse montre qu’il est préférable de considérer individuellement les paramètres des 1re, 2e et 3e composantes plutôt que leur somme pondérée par leurs valeurs propres respectives (chap. 10 et 12). Cette thèse examine également la complémentarité entre les paramètres de structure et ceux relatifs à la puissance rétrodiffusée, souvent ignorée et normalisée par la plupart des décompositions polarimétriques. La dimension temporelle (saisonnière) est essentielle pour la caractérisation et la classification des physionomies végétales (chap. 12, 13 et 14). Des images acquises au printemps (avril et mai) sont nécessaires pour discriminer les milieux secs des milieux humides alors que des images acquises en été (juillet et août) sont nécessaires pour raffiner la classification des physionomies végétales. Un arbre hiérarchique de classification développé dans cette thèse constitue une synthèse des connaissances acquises (chap. 14). À l’aide d’un nombre relativement réduit de paramètres polarimétriques et de règles de décisions simples, il est possible d’identifier, entre autres, trois classes de bas marais et de discriminer avec succès les hauts marais herbacés des autres classes physionomiques sans avoir recours à des sources de données auxiliaires. Les résultats obtenus sont comparables à ceux provenant d’une classification supervisée utilisant deux images Landsat-5 avec une exactitude globale de 77.3% et 79.0% respectivement. Diverses classifications utilisant la machine à vecteurs de support (SVM) permettent de reproduire les résultats obtenus avec l’arbre hiérarchique de classification. L’exploitation d’une plus forte dimensionalitée par le SVM, avec une précision globale maximale de 79.1%, ne permet cependant pas d’obtenir des résultats significativement meilleurs. Finalement, la phase de la décomposition de Touzi apparaît être le seul paramètre (en bande L) sensible aux variations du niveau d’eau sous la surface des tourbières ouvertes (chap. 16). Ce paramètre offre donc un grand potentiel pour le suivi de l’hydrologie des tourbières comparativement à la différence de phase entre les canaux HH et VV. Cette thèse démontre que les paramètres de la décomposition de Touzi permettent une meilleure caractérisation, de meilleures séparabilités et de meilleures classifications des physionomies végétales des milieux humides que les canaux de polarisation HH, HV et VV. Le regroupement des espèces végétales en classes physionomiques est un concept valable. Mais certaines espèces végétales partageant une physionomie similaire, mais occupant un milieu différent (haut vs bas marais), ont cependant présenté des différences significatives quant aux propriétés de leur rétrodiffusion. / Wetlands fill many important ecological functions and contribute to the biodiversity of fauna and flora. Although there is a growing recognition of the importance to protect these areas, it remains that their integrity is still threatened by the pressure of human activities. The inventory and the systematic monitoring of wetlands are a necessity and remote sensing is the only realistic way to achieve this goal. The primary objective of this thesis is to contribute and improve the wetland characterization using satellite polarimetric data acquired in L (ALOS-PALSAR) and C (RADARSAT-2) band. This thesis is based on two hypotheses (Ch. 1). The first hypothesis stipulate that classes of plant physiognomies, based on plant structure, are more appropriate than classes of plant species because they are best adapted to the information content of polarimetric radar data. The second hypothesis states that polarimetric decomposition algorithms allow an optimal extraction of polarimetric information compared to a multi-polarized approach based on the HH, HV and VV channels (Ch. 3). In particular, the contribution of the incoherent Touzi decomposition for the inventory and monitoring of wetlands is examined in detail. This decomposition allows the characterization of the scattering type, its phase, orientation, symmetry, degree of polarization and the backscattered power of a target with a series of parameters extracted from an analysis of the coherency matrix eigenvectors and eigenvalues. The lake Saint-Pierre region was chosen as the study site because of the great diversity of its wetlands that are covering more than 20 000 ha. One of the challenges posed by this thesis is that there is neither a standard system enumerating all the possible physiognomic classes nor an accurate description of their characteristics and dimensions. Special attention was given to the creation of these classes by combining several data sources and more than 50 plant species were grouped into nine physiognomic classes (Ch. 7, 8 and 9). Several analyzes are proposed to validate the hypotheses of this thesis (Ch. 9). Sensitivity analysis using scatter plots are performs to study the characteristics and dispersion of plant physiognomic classes in various features space consisting of polarimetric parameters or polarization channels (Ch. 10 and 12). Time series of made of RADARSAT-2 images are used to deepen the understanding of the seasonal evolution of plant physiognomies (Ch. 12). The transformed divergence algorithm is used to quantify the separability between physiognomic classes and to identify the parameters (s) that contribute the most to their separability (Ch. 11 and 13). Classifications are also proposed and the results compared to an existing map of the lake Saint-Pierre wetlands (Ch. 14). Finally, an analysis of the potential of polarimetric parameters in C and L-band is proposed for the monitoring of peatlands hydrology (Ch. 15 and 16). Sensitivity analyses show that the parameters of the 1st component, relative to the dominant (polarized) part of the signal, are sufficient for a general characterization of plant physiognomies. The parameters of the second and third components are, however, needed for better class separability (Ch. 11 and 13) and a better discrimination between wetlands and uplands (Ch. 14). This thesis shows that it is preferable to consider individually the parameters of the 1st, 2nd and 3rd components rather than their weighted sum by their respective eigenvalues (Ch. 10 and 12). This thesis also examines the complementarity between the structural parameters and those related to the backscattered power, often ignored and normalized by most polarimetric decomposition. The temporal (seasonal) dimension is essential for the characterization and classification of plant physiognomies (Ch. 12, 13 and 14). Images acquired in spring (April and May) are needed to discriminate between upland and wetlands while images acquired in summer (July and August) are needed to refine the classifications of plant physiognomies. A hierarchical classification tree developed in this thesis represents a synthesis of the acquired knowledge (Chapter 14). Using a relatively small number of polarimetric parameters and simple decision rules, it is possible to identify, among other, three low marshes classes and to discriminate with success herbaceous high marshes from other physiognomic classes without using ancillary data source. The results obtained are comparable to those from a supervised classification using two Landsat-5 images with an overall accuracy of 77.3% and 79.0% respectively. Various classifications using the support vector machine (SVM) can reproduce the results obtained with the hierarchical classification tree. But the possible exploitation by the SVM of a higher dimensionality, with a maximum overall accuracy of 79.1%, does not allow however to achieve significantly better results. Finally, the phase of the Touzi decomposition appears to be the only parameter (in L-band) sensitive to changes in water level beneath the peat surface (Ch. 16). Therefore, this parameter offer a great potential for peatlands hydrology monitoring compared to the HH-VV phase difference. This thesis demonstrates that the Touzi decomposition parameters allow a better characterization, better separability and better classifications of wetlands plant physiognomic classes than HH, HV and VV polarization channels. The grouping of plant species into physiognomic classes is a valid concept. However, some plant species sharing a similar physiognomy, but occupying a different environment (high vs. low marshes), have presented significant differences in their scattering properties.

No description available.

Ground-based weather radars provide information on the temporal evolution and the spatial distribution of precipitation on a macroscopic scale over a large area. However, the echoes measured by weather radars are always a superposition of forward and backward scattering effects which complicates their interpretation. The use of polarisation diversity enhances the number of independent observables measured simultaneously. This allows an effective separation of forward and backward scattering effects. Furthermore, it extends the capability of weather radars to retrieve also microphysical information about the precipitation. The dissertation at hand introduces new aspects in the field of polarimetric, ground-based, monostatic weather radars at S-, C-, and X-band. Relations are provided to change the polarisation basis of reflectivities. A fully polarimetric weather radar measurement at circular polarisation basis is analysed. Methods to check operationally the polarimetric calibration of weather radars operating at circular polarisation basis are introduced. Moreover, attenuation correction methods for weather radar measurements at linear horizontal / vertical polarisation basis are compared to each other, and the robustly working methods are identified. / Bodengebundene Wetterradare bieten Informationen über die zeitliche Entwicklung und die räumliche Verteilung von Niederschlag in einer makroskopischen Skala über eine große Fläche. Die Interpretation der Wetterradarechos wird erschwert, da sie sich aus einer Überlagerung von Vorwärts- und Rückwärtsstreueffekten ergeben. Die Anzahl der unabhängigen Wetterradarmessgrößen kann durch den Einsatz von Polarisationsdiversität erhöht werden. Dies ermöglicht eine effektive Trennung von Vorwärts- und Rückwärtsstreueffekten. Desweiteren erlaubt es die Bestimmung von mikrophysikalischen Niederschlagsparametern. Die vorliegende Dissertation betrachtet neue Aspekte für polarimetrische, bodengebundene, monostatische Wetterradare im S-, C- und X-Band. Gleichungen zur Polarisationsbasistransformation von Reflektivitätsmessungen werden eingeführt. Eine vollpolarimetrische Wetterradarmessung in zirkularer Polarisationsbasis wird analysiert. Neue Methoden, die eine Überprüfung der polarimetrischen Kalibrierung von Wetterradarmessungen in zirkularer Polarisationsbasis erlauben, werden betrachtet. Weiterhin werden Methoden zur Dämpfungskorrektur von Wetterradarmessungen in linearer horizontaler / vertikaler Polarisationsbasis miteinander verglichen und Empfehlungen von zuverlässigen Methoden gegeben.