Today digital TV receivers (Set-Top-Boxes) are mainly controlled by IR-based remote control units (RCUs). With new services emerging in thereceivers where better browsing and pointing abilities are desirable (VODservices, Web services, games etc), one solution is a new type of RF remotecontrol. An RF RCU has a number of advantages, e.g. when in range, ithas 100% reliable transmission, it is not sensitive to direction, and it doesnot require a free way to the receiver (i.e. it allows the receiver to be hiddenbehind the TV-set or in a cabinet).

<p>Typical imaging systems rely on the interactions of matter with electromagnetic radiation, which can lead to scattered waves that are radiated away from the imaging area. The goal such an imaging device is to collect these radiated waves and focus them onto a measurement detector that is sensitive to the wave's properties such as wavelength (or color) and intensity. The detector's measurements of the scattered fields are then used to reconstruct spatial information about the original matter such as its shape or location. However, when a scattered wave is collected by the imaging device, it diffracts and inteferes with itself. The resulting interference pattern can blur spatial information of the reconstructed image. This leads to a so-called diffraction limit, which describes the minimum sizes of spatial features on a scatterer that can be resolved using conventional imaging techniques. The diffraction limit scales with the wavelength &lambda; of the illuminating field, where the limit for conventional imaging with visible light is approximately 200 nm. Investigating subwavelength objects (< &lambda;) requires more advanced measurement techniques, and improving the resolving capabilities of imaging devices continues to be an active area of research.</p><p>Here, I describe a new sensing technique for resolving the position of a subwavelength scatterer (< &lambda;) with vastly subwavelength resolution (<< &lambda;). My approach combines two separate fields of scientific inquiry: time-delayed nonlinear feedback and wave chaos. In typical time-delayed nonlinear feedback systems, the output of a nonlinear device is delayed and fed back to its input. In my experiment, the output of a radio-frequency (&lambda; ~ 15 cm) nonlinear circuit is injected into a complex scattering environment known as a wave-chaotic cavity. Inside the cavity, the field interacts with a subwavelength dielectric object from all sides, and a portion of the scattered waves are coupled out of the cavity, amplified, and fed back to the input of the nonlinear circuit. The resulting closed-feedback loop generates its own radio-frequency illumination field (> 1 GHz), which contains multiple wavelengths and is sensitive to location of the scattering object. Using the dynamical changes in the illumination field, I demonstrate subwavelength position-sensing of the scatterer's location in the cavity with a one-dimensional resolution of ~&lambda;/10,000 and a two-dimensional resolution of ~ &lambda;/300. </p><p>This novel method demonstrates that the dynamical changes of a feedback oscillator can be exploited for resolving subwavelength spatial features. Unlike conventional imaging techniques, it uses a single scalar measurement of the scattered field and takes advantage of a complex scattering environment. Furthermore, this work demonstrates the first application of quasiperiodic dynamics (oscillations with incommensurate frequencies) from a nonlinear system. Using the key ingredients from my radio-frequency system, I extend my method to an experiment that uses optical frequencies (&lambda; = 1550 nm) to demonstrate subwavelength sensing in two dimensions with a resolution of approximately 10 nm. Because this new sensing technique can be adapted to multiple experiments over vastly different length scales, it represents a potential platform for creating a new class subwavelength imaging devices.</p> / Dissertation

No description available.

The purpose of this research was development of a geographic information system (GIS) and linkage with existing ground-water models to expedite wellhead protection area (WHPA) delineation within a wellhead protection (WHP) program. Research objectives included: (1) incorporation of relevant data from federal, state, and local agencies into the database; (2) delineation of WHPAs utilizing linkage established at Rice University between the GIS and WHPA (a ground-water model which delineates capture zones); (3) evaluation of model input parameter sensitivities to address effects of parameter input on the shape of delineated WHPAs; (4) demonstration of the utility of the GIS to facilitate WHPA delineation; and (5) development of a prototype ground-water management system. Harris County, Texas, already identified as a critical ground-water supply area, was selected as the project area. Public water well data on 224 City of Houston wells served as the initial dataset for the development of a county-wide WHP program.

Soil erosion is a complex, natural process that often is accelerated by such human activities as land clearance, agriculture, construction, and surface mining. Accurate soil erosion type/intensity maps can be effective tools in aid of soil erosion control efforts. / The principal objective of this research was to use geographic information system (GIS) and remotely sensed data to extract and define erosion types/intensities over a large area (4,511.8 km2) in Iran. The study proceeded in three major steps: (i) a 10-m resolution digital elevation model (DEM), land slope, elevation range, and stream network pattern were created. These basic identifying parameters plus Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images were used to differentiate various landforms, (ii) a land use and land cover map was created based on analysis of three Landsat Enhanced Thematic Mapper (ETM+) images from the growing season plus use of a landform map and climatic zones as ancillary information, and (iii) in order to extract and identify various erosion types/intensities, the difference in brightness combination over two growing season intervals derived from the Landsat ETM+ images were used. Further, land slope, landform, land use, and land cover layers were used to assist in the classification of the erosion types (interrill and rill). / The approach presented produced soil erosion type/intensity maps with an overall accuracy of 93.4%. Considering only rangeland and forest a unique relationship exists between seasonal brightness combinations and erosion intensity. It was found that for the lower erosion levels it is the later season or second brightness combination (BJS) which indicates degree of erosion intensity, but for the areas of severe and very severe erosion it is the early season or first brightness combination (BMJ) that differentiates degree of erosion intensity. Further, this study illustrated that land use, land cover, landform, and land slope layers can be used for differentiating erosion types. / The approach presented has been shown to be an effective tool for the creation of soil erosion maps over a large area of Iran and is expected to be useful for aiding in the development of soil conservation and watershed management plans in other areas. The main advantages of this approach are accuracy, lower demands on time and funds for field work and ready availability of required data for many regions of the world. / Processus naturel complexe, l'érosion du sol est fréquemment exacerbée par les activités anthropiques telles le défrichage, l'agriculture, la construction, et l'exploitation minière à ciel ouvert. Une cartographie précise du type et de l'intensité d'érosion du sol peut s'avérer un outil efficace dans une lutte contre l'érosion. / Les présentes recherches visèrent l'utilisation de SIG et de données de télédétection dans la localisation et l'identification de divers types d'érosion sur une aire de grande étendue (4,511.8 km2) en Iran. L'étude s'échelonna sur trois étapes: (i) un modèle altimétrique numérique (MAN) d'une résolution de 10 m servit à créer des plans de pente du terrain, d'altitude, et du tracé hydrographique. Différentes formes de relief furent différenciés grâce à ces paramètres identificateurs et à des images provenant de radiomètre spatial de pointe pour l'étude de la réflectance et des émissions thermiques terrestres (ASTER), (ii) une carte d'affectation et de couvert du sol fut tracée selon l'analyse de trois images Landsat ETM+ prises durant la saison de croissance ainsi que des informations supplémentaires tirés de cartes de relief et de zones climatiques, et (iii) la différence dans la combinaison de brillances provenant d'images Landsat ETM+, lors de deux intervalles de la saison de croissance, servit à extraire et identifier les différents types et intensités d'érosion. Les plans de pente du terrain, de relief, ainsi que ceux d'affectation et couvert du sol, appuyèrent l'identification du type d'érosion (rigoles et entre-rigoles). / Cette approche généra des cartes de type et d'intensité d'érosion d'une exactitude globale de 93.4%. Ne prenant en compte que les parcours et forêts, il devient apparent qu'il existe un lien tout particulier entre la combinaison de brillances saisonnières et le taux d'érosion. Pour les niveaux d'érosions moins élevés c'est la seconde combinaison de brillances (BJS), qui prévale en fin de saison, qui est la plus fortement liée au niveau d'intensité de l'érosion, tandis que pour les zones d'érosion sévères et très sévères c'est la première combinaison de brillances (BMJ), qui prévale en début de saison, qui permet de différencier le niveau d'intensité de l'érosion. Cette étude indique que l'affectation et le couvert du sol, le relief et les pentes du terrain peuvent servir à différencier divers types d'érosion. / Nous avons démontré que la démarche préconisée représente un outil efficace dans la création de cartes d'érosion à grande échelle pour l'Iran, et nous nous attendons qu'elle s'avèrera utile au développement de politiques de conservation du sol et de gestion des bassins versants dans d'autres régions. Les principaux avantages de cette démarche sont sa précision, ses moindres exigences au niveau du temps sur le terrain et coûts associés, ainsi que la disponibilité accrue des données nécessaires de par le monde.

The photochemical reflectance index (PRI) is a remotely sensed vegetation index that detects a decrease in spectral reflectance at 531nm associated with xanthophyll cycle activity. PRI has been shown to track light use efficiency (LUE) in a number of plant species. PRI shows great promise in improving our ability to sense photosynthetic fluxes of CO2 remotely. However, it has not been tested in all environments, and its applicability is particularly uncertain for peatland environments dominated by mosses. This research investigates the ability of PRI to track LUE in a boreal forest and peatland, and examines the spectral signal associated with xanthophyll cycle activity in heterogeneous peatland plots. This research also investigates the relationship between PRI and leaf area index (LAI) over space and time in a peatland. We found most plots examined in the peatland site did not exhibit a spectral signal associated with xanthophyll cycle activity when exposed to a transition from dark conditions to full sunlight. This transition should lead to a de-epoxidation of xanthophylls in leaf tissues and a decrease in reflectance at 531nm. Plots that did show the decrease in reflectance at 531nm after this change in light conditions also displayed a decrease in PRI. This indicates that PRI effectively detects the 531nm signal as well as xanthophyll cycle activity and light stress in these plots. However, the variability in the strength of the spectral response to changing light conditions may confound the PRI signal in practice, and make it difficult to interpret results of airborne or satellite data. We also found PRI at the peatland site to be sensitive to and directly correlated with spatial variability in LAI, and negatively correlated with temporal variability in LAI. These characteristics may result in further difficulties applying PRI in peatlands. PRI and LUE were correlated at both the forest and peatland site, however at both sites the PRI signal saturated around 500 µmol m-2 s-1 of photosynthetically active radiation (PAR). This saturation effect has not, to our knowledge, been reported in other studies. Saturation of the PRI signal may limit our ability to determine carbon fluxes from airborne or satellite based remotely sensed data which is generally collected under clear skies during the brightest parts of the day when PAR exceeds 500 µmol m-2 s-1. / L'indice de réflectance photochimique (IRP) est un indice de végétation par télédétection qui détecte une diminution de la réflectance spectrale à 531nm associée à l'activité du cycle des xanthophylles. Il a été démontré que l'IRP est associé à l'efficacité d'utilisation de lumière (EUL) dans un certain nombre d'espèces végétales. L'IRP permet donc d'améliorer notre capacité à détecter les flux photosynthétiques du CO2 à distance. Cependant, il n'a pas été testé dans tous les environnements, et son applicabilité est particulièrement incertaine pour les écosystèmes tels que les tourbières dominées par les mousses. Cette étude examine la capacité des IRP de déceler l'EUL dans une forêt boréale et une tourbière, et examine le signal spectral associé à l'activité du cycle xanthophylle dans des parcelles hétérogènes d'une tourbière. Cette étude explore également la relation entre l'IRP et l'indice de surface foliaire (ISF) dans l'espace et le temps dans une tourbière.Nous avons trouvé que la plupart des parcelles examinées dans la tourbière ne présentent pas un signal spectral associé à l'activité du cycle de xanthophylle lorsqu'exposées à des conditions passant de l'obscurité à la lumière du soleil. Cette transition de luminosité devrait mener à la de-époxydation des xanthopylles dans les tissus foliaires et à une diminution de la réflectance à 531 nm. Les parcelles qui ont montré une telle diminution de la réflectance à 531 nm après les changements de luminosité ont aussi affiché une baisse de l'IRP. Ceci indique que l'IRP peut détecter le signal à 531 nm ainsi que l'activité du cycle de xanthophylle et le stress lumineux dans ces parcelles. Par contre, la variabilité de la réponse spectrale à l'évolution des conditions de lumière peuvent confondre le signal de l'IRP, ce qui rend difficile d'interpréter les résultats provenant de données aériennes ou satellitaires. Nous avons également constaté que l'IRP dans la tourbière est sensible et directement corrélé avec la variabilité spatiale de l'ISF, et négativement corrélé avec la variabilité temporelle de l'ISF. Ces caractéristiques peuvent entraîner des difficultés supplémentaires quant à l'application de l'IRP dans les tourbières.L'IRP et l'EUL étaient corrélés à la forêt et à la tourbière, mais il y avait saturation du signal de l'IRP autour de 500 µmol m-2 s-1 du rayonnement photosynthétiquement actif (RPA) aux deux sites. Cet effet de saturation n'a pas, à notre connaissance, été signalé dans d'autres études. La saturation du signal de l'IRP peut limiter notre capacité à déterminer les flux de carbone provenant de données aériennes ou satellitaires qui sont généralement recueillies sous un ciel clair pendant les parties les plus brillantes de la journée où la RPA dépasse 500 µmol m-2 s-1.

In this work, the various sources of errors in radar rain estimation are quantified and procedures are developed to reduce them. The few topics explored here are: the variability of drop size distributions (DSDs), radar calibration, and errors in polarimetric rain estimation. The findings resulting from this study include 1) a new filtering technique that reduces the spurious DSD sampling variability while maintaining the physical variability, 2) a generalization of previously suggested DSD models in terms of scaling concepts, 3) the experimental evidence of the physical interpretation of DSD evolution and of R-Z relationships, 4) the time scale dependence of the DSD variability and its implication for radar rain estimation, 5) the quantification of error sources in polarimetric rain estimation and its feasibility in operational environment, and 6) a complete set of stable radar calibration methods and their theoretical limits. All error statistics from this work will be used as a guideline in radar rain estimation.

The estimation or modeling of biophysical variables such as surface roughness, vegetation phytomass, and soil moisture in the Arctic is an important step towards understanding arctic energy fluxes, effects of changing climate, and hydrological patterns. This research uses Synthetic Aperture Radar (SAR) data, along with ancillary optical and environmental data, to create models that estimate these biophysical variables across different High Arctic landscapes, with the goal of applying the models across even larger areas. Field work was conducted at two High Arctic locations on Melville Island, Nunavut, Canada. At each location, surface roughness values were measured at a number of randomized plot locations using a pin meter. Soil moisture values were measured using a time domain reflectometry (TDR) instrument within six hours of multiple overpasses of the RADARSAT-2 SAR sensor. Surface roughness models were generated with multi-incidence angle and fully polarimetric SAR data, with resulting R2 values ranging between 0.39 and 0.66, and normalized root mean squared error (N_RMSE) values of 14% - 22%. The output from the final surface roughness model was used as an input to the soil moisture models. Vegetation phytomass was modeled with multi-angular SAR data, using a soil adjusted vegetation index (SAVI) derived from optical data across the study area as a measure of verification. The resulting model had a significant (p <0.05) relationship to the SAVI values, with an R2 of 0.60. This model was then compared to field-collected above-ground phytomass values, and a model was derived that related SAR data directly to phytomass. This model again showed a strong relationship, with an R2 value of 0.87. The final biophysical variable that was modeled, soil moisture, showed moderate agreement to field-measured soil moisture values (R2 = 0.46, N_RMSE = 0.15%), but much stronger relationships were found for relative moisture values at fine scales across the landscape. These models, when taken together, demonstrate that SAR data is capable of modeling biophysical variables across high latitude environments. These models will help address larger questions, such as how SAR can be used to better understand moisture and energy exchanges over regional areas in high arctic environments. / Thesis (Ph.D, Geography) -- Queen's University, 2014-02-03 16:52:26.856

Stephens Lake, Manitoba is an example of a peatland reservoir that has undergone physical changes related to mineral erosion and peatland disintegration processes since its initial impoundment. In this thesis I focused on the processes of peatland upheaval, transport, and disintegration as the primary drivers of dynamic change within the reservoir. The changes related to these processes are most frequent after initial reservoir impoundment and decline over time. They continue to occur over 35 years after initial flooding. I developed a remote sensing approach that employs both optical and microwave sensors for discriminating land (i.e. floating peatlands, forested land, and barren land) from open water within the reservoir. High spatial resolution visible and near-infrared (VNIR) optical data obtained from the QuickBird satellite, and synthetic aperture radar (SAR) microwave data obtained from the RADARSAT-1 satellite were implemented. The approach was facilitated with a Geographic Information System (GIS) based validation map for the extraction of optical and SAR pixel data. Each sensor’s extracted data set was first analyzed separately using univariate and multivariate statistical methods to determine the discriminant ability of each sensor. The initial analyses were followed by an integrated sensor approach; the development of an image classification model; and a change detection analysis. Results showed excellent (> 95%) classification accuracy using QuickBird satellite image data. Discrimination and classification of studied land cover classes using SAR image texture data resulted in lower overall classification accuracies (~ 60%). SAR data classification accuracy improved to > 90% when classifying only land and water, demonstrating SAR’s utility as a land and water mapping tool. An integrated sensor data approach showed no considerable improvement over the use of optical satellite image data alone. An image classification model was developed that could be used to map both detailed land cover classes and the land and water interface within the reservoir. Change detection analysis over a seven year period indicated that physical changes related to mineral erosion, peatland upheaval, transport, and disintegration, and operational water level variation continue to take place in the reservoir some 35 years after initial flooding. This thesis demonstrates the ability of optical and SAR satellite image remote sensing data sets to be used in an operational context for the routine discrimination of the land and water boundaries within a dynamic peatland reservoir. Future monitoring programs would benefit most from a complementary image acquisition program in which SAR images, known for their acquisition reliability under cloud cover, are acquired along with optical images given their ability to discriminate land cover classes in greater detail.

Wetlands are recognized as valuable landscapes for their contribution to biodiversity, ecosystem services and population livelihoods. However, current global wetland inventories do not spatially represent wetland extent at a spatial and temporal resolution appropriate for conservation and management purposes. Among the best existing global inventories, the Global Lakes & Wetlands Database (GLWD; Lehner & Döll, 2004) is a static database assembled from various existing data sources that unfortunately suffers from the inconsistency among its data sources. Another, the Global Surface Water Extent Dataset (GSWED; Prigent et al. 2007; Papa et al. 2010) produced from a multi-satellite method is capable of monthly measurements but possesses a coarse spatial resolution incapable of discriminating distinct surface water bodies. Faced with the limitations of current global inventories, a new methodological approach is required to provide the improved wetland inventory needed by the research and conservation communities.This thesis investigates a methodology capable of producing a high-resolution (~ 500 m) surface water extent map by spatially downscaling the coarse resolution (~27 km) inundated area estimates of GSWED. The methodology inspired by Bwangoy et al. (2010) has a pragmatic and straight-forward design to ensure and ease its global application. The work of this thesis consists of an initial implementation and validation of the methodology across the African continent. The downscaling approach relies on the topographic and hydrographic information from the globally available HydroSHEDS data (Lehner et al., 2008) to distribute inundated area at the finer resolution to the most topographically inundation prone areas. Thirteen hydro-topographic variables were computed from HydroSHEDS and then consolidated into a single inundation probability map with the use of decision tree learners. The decision trees were trained on regional inundation maps and subsequently employed to generate a topographic probability of inundation map at high-resolution for the entire continent. The probability map is turned into an inundated/non-inundated map by splitting the probability distribution into two (inundated/non-inundated) with a defined threshold value. A threshold value is chosen for each GSWED cell to produce an inundation map replicating the inundated area estimates of GSWED within the cell at the finer resolution. To represent the maximum wetland extent at different timescales, two sets of inundated areas estimates were downscaled as high-resolution inundation maps with this MWT downscaling procedure: 1) the mean annual maximum (MAMax) estimates were calculated for each cell from the monthly estimates of GSWED between 1993 and 2004; 2) the fusion maximum (MaxFusion) was generated from a fusion of the time-series maximum (TSMax) also calculated from GSWED, with the wetland area from GLWD. The MaxFusion estimates were produced to correct some data gaps of GSWED, as well as to offer a more complete and reliable maximum wetland extent map. The MAMax and MaxFusion estimates respectively totalled 1339 and 2779 thousand km2 of wetland area across the continent; higher than most previous estimates for Africa.Validation of the spatial distribution of inundation at the finer resolution exhibited high levels of agreement against reference regional maps (Overall Accuracy ~ 92%; KIA ~ 80%). Over selected wetland study sites, comparisons of the MaxFusion downscaled map with the global land cover GLC2000 (Mayaux et al. 2004) and wetland database GLWD indicated that the downscaled map possessed slightly lower but more consistent agreement with GLC2000 than GLWD did. Regardless, the level accuracy of the tested methodology is considered satisfactory to pursue production of a first version global inundation map. Possible follow-up applications making use of the downscaled inundation maps such as a global hydro-geomorphic wetland classification. / Bien que l'importance des milieux humides pour la biodiversité et les services écosystémiques soit reconnue, les bases de données actuellement disponibles ne sont pas en mesure de décrire globalement les charactéristiques biophysiques des milieux humides de façon utile à des fins de gestion et de conservation. Parmi les inventaires globaux de milieux humides disponibles, la Global Lake & Wetland Database (GLWD) (Lehner & Döll, 2004), , est une représentation statique constituée de plusieurs sources qui est cependant spatiallement inconsistente. Un autre inventaire, le Global Surface Water Extent Dataset (GSWED) (Prigent et al. 2007; Papa et al. 2010) produite à partir d'une méthode multi-satellitaire, possède une faible résolution spatiale incapable de différencier des plans d'eau distincts. Compte tenue des limites des actuels inventaires, une nouvelle approche est nécessaire pour générer le nouvel et amélioré inventaire que demande diverses communautés de chercheurs.Cette thèse examine la possibilité de produire une représentation spatiale d'inondation et de milieux humides globale à haute résolution (~ 500 m) à partir d'une réduction d'échelle des estimés surfaces inondées de faible résolution (~27 km) du GSWED. La méthode inspirée par Bwangoy et al. (2010) a été développée de façon pragmatique et simple afin d'assurer son application globale sans heurt. Cette thèse est une application initiale de la méthodologie à des fins de validations sur le continent africain. La méthode de réduction de résolution repose sur de l'information topographiques et hydrographiques globales provenant des données HydroSHEDS (Lehner et al. 2008) pour distribuer la surface inondée de GSWED à la plus fine résolution aux endroits les plus prompt à l'inondation. Treize variables hydro-topographiques furent calculées à partir d'HydroSHEDS et ensuite consolidée dans une probabilité d'inondation calculée pour chaque pixel de haute résolution d'HydorSHED,S grâce à un arbre de décision. L'arbre de décision fut entraîné et validé avec des images satellitaires régionales d'inondation et fut utilisé par la suite pour générer des probabilités d'inondation sur l'ensemble du continent. La carte de probabilités d'inondation résultante est ensuite transformée en carte d'inondation en utilisant une valeur seuil divisant la distribution de probabilités en deux. Une valeur seuil est choisie pour la surface de chaque cellule de GSWED pour répliquer la surface inondée de GSWED.En tant qu'estimé de surface provenant de GSWED, les valeurs mensuelles entre 1993 et 2004 furent agrégée pour produire des estimés du maximum annuel moyen (MAMax) ainsi que le maximum historique (TSMax). Pour produire des estimées fiables représentant la surface maximale inondée et pour corriger pour certaines des lacunes des estimés de GSWED, les estimés du TSMax furent fusionnés à celles de GLWD, générant les estimées maximales de fusion (MaxFusion). La surface totale estimée pour l'ensemble du continent africain pour MAMax et MaxFusion est estimées respectivement à 1339 et 2779 milliers de km2, plus élevée que la plupart des estimés précédents.La validation de la distribution spatiale de l'inondation à la plus fine résolution a démontré un bon accord (Précision globale ~ 92%; KIA ~ 80%) lorsque comparée à des cartes régionales d'inondations ou de milieux humides. De plus, la comparaison du résultat cartographique avec le GLC2000 et le GLWD sur quelques sites particuliers a indiqué une concordance avec GLC2000 consistante, malgré qu'inférieure à celle de GLWD. Malgré les défauts du produit, le niveau de précision de la méthodologie testée peut être considérée suffisant pour poursuivre son développement et son application globale. D'autre projets de recherches découlant de celui-ci et faisant usage d'une carte d'inondation global à haute-résolution peuvent avoir faire à un classification hydro-géomorphique de milieux humides.