Strategy to detect ground control in digital images

The identification of ground control on photographs or images is usually carried out by a human operator, who uses his natural skills to make interpretations. In Digital Photogrammetry, which uses techniques of digital image processing extraction of ground control can be automated by using an approach based on relational matching and a heuristic that uses the analytical relation between straight features of object space and its homologous in the image space. A build-in self-diagnosis is also used in this method. It is based on implementation of data snooping statistic test in the process of spatial resection using the Iterated Extended Kalman Filtering (IEKF). The aim of this paper is to present the basic principles of the proposed approach and results based on real data.

Line based camera calibration in machine vision dynamic applications

The problem of dynamic camera calibration considering moving objects in close range environments using straight lines as references is addressed. A mathematical model for the correspondence of a straight line in the object and image spaces is discussed. This model is based on the equivalence between the vector normal to the interpretation plane in the image space and the vector normal to the rotated interpretation plane in the object space. In order to solve the dynamic camera calibration, Kalman Filtering is applied; an iterative process based on the recursive property of the Kalman Filter is defined, using the sequentially estimated camera orientation parameters to feedback the feature extraction process in the image. For the dynamic case, e.g. an image sequence of a moving object, a state prediction and a covariance matrix for the next instant is obtained using the available estimates and the system model. Filtered state estimates can be computed from these predicted estimates using the Kalman Filtering approach and based on the system model parameters with good quality, for each instant of an image sequence. The proposed approach was tested with simulated and real data. Experiments with real data were carried out in a controlled environment, considering a sequence of images of a moving cube in a linear trajectory over a flat surface.

Georeferenced road extraction and formulation of hypotheses for new road segments

The acquisition and update of Geographic Information System (GIS) data are typically carried out using aerial or satellite imagery. Since new roads are usually linked to georeferenced pre-existing road network, the extraction of pre-existing road segments may provide good hypotheses for the updating process. This paper addresses the problem of extracting georeferenced roads from images and formulating hypotheses for the presence of new road segments. Our approach proceeds in three steps. First, salient points are identified and measured along roads from a map or GIS database by an operator or an automatic tool. These salient points are then projected onto the image-space and errors inherent in this process are calculated. In the second step, the georeferenced roads are extracted from the image using a dynamic programming (DP) algorithm. The projected salient points and corresponding error estimates are used as input for this extraction process. Finally, the road center axes extracted in the previous step are analyzed to identify potential new segments attached to the extracted, pre-existing one. This analysis is performed using a combination of edge-based and correlation-based algorithms. In this paper we present our approach and early implementation results.

Um modelo para orientação de imagens orbitais baseado em feições retas

The aim of this paper is to present a model for orientation of pushbroom sensors that allows estimating the polynomial coefficients describing the trajectory of the platform, using linear features as ground control. Considering that pushbroom image acquisition is not instantaneous, six EOP (Exterior Orientation Parameters) for each scanned line must be estimated. The sensor position and attitude parameters are modeled with a time dependent polynomial. The relationship between object and image space is established through a mathematical model based on the equivalence between the vector normal to the projection plane in the image space and to the vector normal to the rotated projection plane in the object space. The equivalence property between planes was adapted to consider the pushbroom geometry. Some experiments with simulated data corresponding to CBERS scene (China-Brazil Earth Resource Satellite) were accomplished in order to test the developed model using straight lines. Moreover, experiments with points ground with the model based on collinearity equations adapted to the pushbroom geometry were also accomplished. The obtained results showed that the proposed model can be used to estimate the EOP of pushbroom images with suitable accuracy.

A semi-automatic method for indirect orientation of aerial images using ground control lines extracted from airborne laser scanner data

This paper presents a method for indirect orientation of aerial images using ground control lines extracted from airborne Laser system (ALS) data. This data integration strategy has shown good potential in the automation of photogrammetric tasks, including the indirect orientation of images. The most important characteristic of the proposed approach is that the exterior orientation parameters (EOP) of a single or multiple images can be automatically computed with a space resection procedure from data derived from different sensors. The suggested method works as follows. Firstly, the straight lines are automatically extracted in the digital aerial image (s) and in the intensity image derived from an ALS data-set (S). Then, correspondence between s and S is automatically determined. A line-based coplanarity model that establishes the relationship between straight lines in the object and in the image space is used to estimate the EOP with the iterated extended Kalman filtering (IEKF). Implementation and testing of the method have employed data from different sensors. Experiments were conducted to assess the proposed method and the results obtained showed that the estimation of the EOP is function of ALS positional accuracy.

Orientação exterior de imagens orbitais usando modelos rigorosos com feições retas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Extração semi-automática da malha viária em imagens aéreas digitais de áreas rurais utilizando otimização por programação dinâmica no espaço objeto

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Modelagem fotogramétrica e calibração de um sistema de visão omnidirecional

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Extração de contornos de telhado de edifícios no espaço-objeto baseada em snakes e programação dinâmica a partir de TIN/laser e imagens aéreas de alta resolução

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Refinamento geométrico de contornos e cumeeiras de telhados de edifícios extraídos de dados laser com uso de imagem aérea

In this paper, a method is proposed to refine the LASER 3D roofs geometrically by using a high-resolution aerial image and Markov Random Field (MRF) models. In order to do so, a MRF description for grouping straight lines is developed, assuming that each projected side contour and ridge is topologically correct and that it is only necessary to improve its accuracy. Although the combination of laser data with data from image is most justified for refining roof contour, the structure of ridges can give greater robustness in the topological description of the roof structure. The MRF model is formulated based on relationships (length, proximity, and orientation) between the straight lines extracted from the image and projected polygon and also on retangularity and corner injunctions. The energy function associated with MRF is minimized by the genetic algorithm optimization method, resulting in the grouping of straight lines for each roof object. Finally, each grouping of straight lines is topologically reconstructed based on the topology of the corresponding LASER scanning polygon projected onto the image-space. The results obtained were satisfactory. This method was able to provide polygons roof refined buildings in which most of its contour sides and ridges were geometrically improved.

Dall'involucro all'invaso. Lo spazio a pianta centrale nell'opera architettonica di Adalberto Libera

An archetype selected over the centuries Adalberto Libera wrote little, showing more inclination to use the project as the only means of verification. This study uses a survey of the project for purely compositional space in relation to the reason that most other returns with continuity and consistency throughout his work. "The fruit of a type selected over centuries", in the words of Libera, is one of the most widely used and repeated spatial archetypes present in the history of architecture, given its nature as defined by a few consolidated elements and precisely defined with characters of geometric precision and absoluteness, the central space is provided, over the course of evolution of architecture, and its construction aspects as well as symbolic, for various uses, from historical period in which it was to coincide with sacred space for excellence, to others in which it lends itself to many different expressive possibilities of a more "secular". The central space was created on assumptions of a constructive character, and the same exact reason has determined the structural changes over the centuries, calling from time to time with advances in technology, the maximum extent possible and the different applications, which almost always have coincided with the reason for the monumental space. But it’s in the Roman world that the reason for the central space is defined from the start of a series of achievements that fix the character in perpetuity. The Pantheon was seen maximum results and, simultaneously, the archetype indispensable, to the point that it becomes difficult to sustain a discussion of the central space that excludes. But the reason the space station has complied, in ancient Rome, just as exemplary, monuments, public spaces or buildings with very different implications. The same Renaissance, on which Wittkower's proving itself once and for all, the nature and interpretation of sacred space station, and thus the symbolic significance of that invaded underlying interpretations related to Humanism, fixing the space-themed drawing it with the study and direct observation by the four-sixteenth-century masters, the ruins that in those years of renewed interest in the classical world, the first big pieces of excavation of ancient Rome brought to light with great surprise of all. Not a case, the choice to investigate the architectural work of Libera through the grounds of the central space. Investigating its projects and achievements, it turns out as the reason invoked particularly evident from the earliest to latest work, crossing-free period of the war which for many authors in different ways, the distinction between one stage and another, or the final miss. The theme and the occasion for Libera always distinct, it is precisely the key through which to investigate her work, to come to discover that the first-in this case the central plan-is the constant underlying all his work, and the second reason that the quota with or at the same time, we will return different each time and always the same Libera, formed on the major works remained from ancient times, and on this building method, means consciously, that the characters of architectural works, if valid, pass the time, and survive the use and function contingent. As for the facts by which to formalize it, they themselves are purely contingent, and therefore available to be transferred from one work to another, from one project to another, using also the loan. Using the same two words-at-issue and it becomes clear now how the theme of this study is the method of Libera and opportunity to the study of the central space in his work. But there is one aspect that, with respect to space a central plan evolves with the progress of the work of Libera on the archetype, and it is the reason behind all the way, just because an area built entirely on reason centric. It 'just the "center" of space that, ultimately, tells us the real progression and the knowledge that over the years has matured and changed in Libera. In the first phase, heavily laden with symbolic superstructure, even if used in a "bribe" from Free-always ill-disposed to sacrifice the idea of architecture to a phantom-center space is just the figure that identifies the icon represents space itself: the cross, the flame or the statue are different representations of the same idea of center built around an icon. The second part of the work of clearing the space station, changed the size of the orders but the demands of patronage, grows and expands the image space centric, celebratory nature that takes and becomes, in a different way, this same symbol . You see, one in all, as the project of "Civiltà Italiana" or symbolic arch are examples of this different attitude. And at the same point of view, you will understand how the two projects formulated on the reuse of the Mausoleum of Augustus is the key to its passage from first to second phase: the Ara Pacis in the second project, making itself the center of the composition "breaks" the pattern of symbolic figure in the center, because it is itself an architecture. And, in doing so, the transition takes place where the building itself-the central space-to become the center of that space that itself creates and determines, by extending the potential and the expressiveness of the enclosure (or cover) that defines the basin centered. In this second series of projects, which will be the apex and the point of "crisis" in the Palazzo dei Congressi all'E42 received and is no longer so, the symbol at the very geometry of space, but space itself and 'action' will be determined within this; action leading a movement, in the case of the Arco simbolico and the "Civiltà Italiana" or, more frequently, or celebration, as in the great Sala dei Recevimenti all’E42, which, in the first project proposal, is represented as a large area populated by people in suits, at a reception, in fact. In other words, in this second phase, the architecture is no longer a mere container, but it represents the shape of space, representing that which "contains". In the next step-determining the knowledge from which mature in their transition to post-war-is one step that radically changes the way centric space, although formally and compositionally Libera continues the work on the same elements, compounds and relationships in a different way . In this last phase Freedom, center, puts the man in human beings, in the two previous phases, and in a latent, were already at the center of the composition, even if relegated to the role of spectators in the first period, or of supporting actors in the second, now the heart of space. And it’s, as we shall see, the very form of being together in the form of "assembly", in its different shades (up to that sacred) to determine the shape of space, and how to relate the parts that combine to form it. The reconstruction of the birth, evolution and development of the central space of the ground in Libera, was born on the study of the monuments of ancient Rome, intersected on fifty years of recent history, honed on the constancy of a method and practice of a lifetime, becomes itself, Therefore, a project, employing the same mechanisms adopted by Libera; the decomposition and recomposition, research synthesis and unity of form, are in fact the structure of this research work. The road taken by Libera is a lesson in clarity and rationality, above all, and this work would uncover at least a fragment.

Hierarchical Markov Random Fields Applied to Model Soft Tissue Deformations on Graphics Hardware

Many methodologies dealing with prediction or simulation of soft tissue deformations on medical image data require preprocessing of the data in order to produce a different shape representation that complies with standard methodologies, such as mass–spring networks, finite element method s (FEM). On the other hand, methodologies working directly on the image space normally do not take into account mechanical behavior of tissues and tend to lack physics foundations driving soft tissue deformations. This chapter presents a method to simulate soft tissue deformations based on coupled concepts from image analysis and mechanics theory. The proposed methodology is based on a robust stochastic approach that takes into account material properties retrieved directly from the image, concepts from continuum mechanics and FEM. The optimization framework is solved within a hierarchical Markov random field (HMRF) which is implemented on the graphics processor unit (GPU See Graphics processing unit ).

NEW TOOLS FOR MONITORING GAMMA CAMERA UNIFORMITY

Detector uniformity is a fundamental performance characteristic of all modern gamma camera systems, and ensuring a stable, uniform detector response is critical for maintaining clinical images that are free of artifact. For these reasons, the assessment of detector uniformity is one of the most common activities associated with a successful clinical quality assurance program in gamma camera imaging. The evaluation of this parameter, however, is often unclear because it is highly dependent upon acquisition conditions, reviewer expertise, and the application of somewhat arbitrary limits that do not characterize the spatial location of the non-uniformities. Furthermore, as the goal of any robust quality control program is the determination of significant deviations from standard or baseline conditions, clinicians and vendors often neglect the temporal nature of detector degradation (1). This thesis describes the development and testing of new methods for monitoring detector uniformity. These techniques provide more quantitative, sensitive, and specific feedback to the reviewer so that he or she may be better equipped to identify performance degradation prior to its manifestation in clinical images. The methods exploit the temporal nature of detector degradation and spatially segment distinct regions-of-non-uniformity using multi-resolution decomposition. These techniques were tested on synthetic phantom data using different degradation functions, as well as on experimentally acquired time series floods with induced, progressively worsening defects present within the field-of-view. The sensitivity of conventional, global figures-of-merit for detecting changes in uniformity was evaluated and compared to these new image-space techniques. The image-space algorithms provide a reproducible means of detecting regions-of-non-uniformity prior to any single flood image’s having a NEMA uniformity value in excess of 5%. The sensitivity of these image-space algorithms was found to depend on the size and magnitude of the non-uniformities, as well as on the nature of the cause of the non-uniform region. A trend analysis of the conventional figures-of-merit demonstrated their sensitivity to shifts in detector uniformity. The image-space algorithms are computationally efficient. Therefore, the image-space algorithms should be used concomitantly with the trending of the global figures-of-merit in order to provide the reviewer with a richer assessment of gamma camera detector uniformity characteristics.

Event-based visual servoing

Traditional visual servoing systems have been widely studied in the last years. These systems control the position of the camera attached to the robot end-effector guiding it from any position to the desired one. These controllers can be improved by using the event-based control paradigm. The system proposed in this paper is based on the idea of activating the visual controller only when something significant has occurred in the system (e.g. when any visual feature can be loosen because it is going outside the frame). Different event triggers have been defined in the image space in order to activate or deactivate the visual controller. The tests implemented to validate the proposal have proved that this new scheme avoids visual features to go out of the image whereas the system complexity is reduced considerably. Events can be used in the future to change different parameters of the visual servoing systems.

Development and Optimization of Four-dimensional Magnetic Resonance Imaging (4D-MRI) for Radiation Therapy

A tenet of modern radiotherapy (RT) is to identify the treatment target accurately, following which the high-dose treatment volume may be expanded into the surrounding tissues in order to create the clinical and planning target volumes. Respiratory motion can induce errors in target volume delineation and dose delivery in radiation therapy for thoracic and abdominal cancers. Historically, radiotherapy treatment planning in the thoracic and abdominal regions has used 2D or 3D images acquired under uncoached free-breathing conditions, irrespective of whether the target tumor is moving or not. Once the gross target volume has been delineated, standard margins are commonly added in order to account for motion. However, the generic margins do not usually take the target motion trajectory into consideration. That may lead to under- or over-estimate motion with subsequent risk of missing the target during treatment or irradiating excessive normal tissue. That introduces systematic errors into treatment planning and delivery. In clinical practice, four-dimensional (4D) imaging has been popular in For RT motion management. It provides temporal information about tumor and organ at risk motion, and it permits patient-specific treatment planning. The most common contemporary imaging technique for identifying tumor motion is 4D computed tomography (4D-CT). However, CT has poor soft tissue contrast and it induce ionizing radiation hazard. In the last decade, 4D magnetic resonance imaging (4D-MRI) has become an emerging tool to image respiratory motion, especially in the abdomen, because of the superior soft-tissue contrast. Recently, several 4D-MRI techniques have been proposed, including prospective and retrospective approaches. Nevertheless, 4D-MRI techniques are faced with several challenges: 1) suboptimal and inconsistent tumor contrast with large inter-patient variation; 2) relatively low temporal-spatial resolution; 3) it lacks a reliable respiratory surrogate. In this research work, novel 4D-MRI techniques applying MRI weightings that was not used in existing 4D-MRI techniques, including T2/T1-weighted, T2-weighted and Diffusion-weighted MRI were investigated. A result-driven phase retrospective sorting method was proposed, and it was applied to image space as well as k-space of MR imaging. Novel image-based respiratory surrogates were developed, improved and evaluated.