Efficient topology estimation for large scale optical mapping

Large scale image mosaicing methods are in great demand among scientists who study different aspects of the seabed, and have been fostered by impressive advances in the capabilities of underwater robots in gathering optical data from the seafloor. Cost and weight constraints mean that lowcost Remotely operated vehicles (ROVs) usually have a very limited number of sensors. When a low-cost robot carries out a seafloor survey using a down-looking camera, it usually follows a predetermined trajectory that provides several non time-consecutive overlapping image pairs. Finding these pairs (a process known as topology estimation) is indispensable to obtaining globally consistent mosaics and accurate trajectory estimates, which are necessary for a global view of the surveyed area, especially when optical sensors are the only data source. This thesis presents a set of consistent methods aimed at creating large area image mosaics from optical data obtained during surveys with low-cost underwater vehicles. First, a global alignment method developed within a Feature-based image mosaicing (FIM) framework, where nonlinear minimisation is substituted by two linear steps, is discussed. Then, a simple four-point mosaic rectifying method is proposed to reduce distortions that might occur due to lens distortions, error accumulation and the difficulties of optical imaging in an underwater medium. The topology estimation problem is addressed by means of an augmented state and extended Kalman filter combined framework, aimed at minimising the total number of matching attempts and simultaneously obtaining the best possible trajectory. Potential image pairs are predicted by taking into account the uncertainty in the trajectory. The contribution of matching an image pair is investigated using information theory principles. Lastly, a different solution to the topology estimation problem is proposed in a bundle adjustment framework. Innovative aspects include the use of fast image similarity criterion combined with a Minimum spanning tree (MST) solution, to obtain a tentative topology. This topology is improved by attempting image matching with the pairs for which there is the most overlap evidence. Unlike previous approaches for large-area mosaicing, our framework is able to deal naturally with cases where time-consecutive images cannot be matched successfully, such as completely unordered sets. Finally, the efficiency of the proposed methods is discussed and a comparison made with other state-of-the-art approaches, using a series of challenging datasets in underwater scenarios

A proposal to estimate the motion of an underwater vehicle through visual mosaicking

This thesis proposes a solution to the problem of estimating the motion of an Unmanned Underwater Vehicle (UUV). Our approach is based on the integration of the incremental measurements which are provided by a vision system. When the vehicle is close to the underwater terrain, it constructs a visual map (so called "mosaic") of the area where the mission takes place while, at the same time, it localizes itself on this map, following the Concurrent Mapping and Localization strategy. The proposed methodology to achieve this goal is based on a feature-based mosaicking algorithm. A down-looking camera is attached to the underwater vehicle. As the vehicle moves, a sequence of images of the sea-floor is acquired by the camera. For every image of the sequence, a set of characteristic features is detected by means of a corner detector. Then, their correspondences are found in the next image of the sequence. Solving the correspondence problem in an accurate and reliable way is a difficult task in computer vision. We consider different alternatives to solve this problem by introducing a detailed analysis of the textural characteristics of the image. This is done in two phases: first comparing different texture operators individually, and next selecting those that best characterize the point/matching pair and using them together to obtain a more robust characterization. Various alternatives are also studied to merge the information provided by the individual texture operators. Finally, the best approach in terms of robustness and efficiency is proposed. After the correspondences have been solved, for every pair of consecutive images we obtain a list of image features in the first image and their matchings in the next frame. Our aim is now to recover the apparent motion of the camera from these features. Although an accurate texture analysis is devoted to the matching pro-cedure, some false matches (known as outliers) could still appear among the right correspon-dences. For this reason, a robust estimation technique is used to estimate the planar transformation (homography) which explains the dominant motion of the image. Next, this homography is used to warp the processed image to the common mosaic frame, constructing a composite image formed by every frame of the sequence. With the aim of estimating the position of the vehicle as the mosaic is being constructed, the 3D motion of the vehicle can be computed from the measurements obtained by a sonar altimeter and the incremental motion computed from the homography. Unfortunately, as the mosaic increases in size, image local alignment errors increase the inaccuracies associated to the position of the vehicle. Occasionally, the trajectory described by the vehicle may cross over itself. In this situation new information is available, and the system can readjust the position estimates. Our proposal consists not only in localizing the vehicle, but also in readjusting the trajectory described by the vehicle when crossover information is obtained. This is achieved by implementing an Augmented State Kalman Filter (ASKF). Kalman filtering appears as an adequate framework to deal with position estimates and their associated covariances. Finally, some experimental results are shown. A laboratory setup has been used to analyze and evaluate the accuracy of the mosaicking system. This setup enables a quantitative measurement of the accumulated errors of the mosaics created in the lab. Then, the results obtained from real sea trials using the URIS underwater vehicle are shown.

MOSAICS: Multiplexed Optimal Signal Acquisition Involving Compressed Sensing

It is possible to sample signals at sub-Nyquist rate and still be able to reconstruct them with reasonable accuracy provided they exhibit local Fourier sparsity. Underdetermined systems of equations, which arise out of undersampling, have been solved to yield sparse solutions using compressed sensing algorithms. In this paper, we propose a framework for real time sampling of multiple analog channels with a single A/D converter achieving higher effective sampling rate. Signal reconstruction from noisy measurements on two different synthetic signals has been presented. A scheme of implementing the algorithm in hardware has also been suggested.

La pintura del segle XVIII. La construcció de la festa galant: vers la civilització

Materials didàctics del grup d'investigació Observatori sobre la Didàctica de les Arts (ODAS)

La pintura del segle XVIII. La construcció de la festa galant: la Commedia dell'Arte

Matrials didàctics del grup d'investigació Observatori sobre la Didàctica de les Arts (ODAS)

Dise??o y construcci??n de p??ginas web educativas

Se presenta experiencia educativa que muestra una comunicaci??n realizada por el grupo de trabajo perteneciente al CEP de Granada, que pretende hacer reflexionar sobre el camino recorrido para la elaboraci??n de una web educativa. Se realiza en el CEIP Virgen de la Paz en Otura, Granada. Los objetivos son: favorecer la comunicaci??n en el entorno de la comunidad educativa; adquisici??n de los conocimientos necesarios para la realizaci??n de la web; sentar las bases necesarias para realizar el mantenimiento de la web; aportar al resto de profesorado materiales y programas educativos para los distintos niveles y ??reas.

La construcci??n de una nueva cultura en centros educativos

El F??rum Europeo de Administradores de la Educaci??n celebr?? en Murcia sus octavas jornadas estatales sobre el tema de la construcci??n de la nueva cultura en centros educativos. El libro recoge las ponencias principales y las presentadas en las mesas tem??ticas. Las principales fueron: culturas escolares, reformas e innovaciones: entre la tradici??n y el cambio (Antonio Vi??ao Frago); La participaci??n de la comunidad educativa en la gesti??n y planificaci??n de los centros: Autonom??a y liderazgo democr??tico (Manuel Lorenzo Delgado) y Marketing social de la escuela: Meras reflexiones con propuestas tentativas (Ismael Quintanilla).

Atenci??n a la diversidad : construcci??n de un proyecto curricular integrado

El libro presenta los fundamentos te??rico-pedag??gicos para la construcci??n de un proyecto curricular integrado que atienda a la diversidad y a las necesidades educativas especiales en los centros de primaria y de secundaria, tanto a trav??s de las medidas ordinarias de atenci??n a la diversidad como extraordinarias (adaptaciones curriculares), prestando especial atenci??n a los programas de diversificaci??n curricular de la ESO. Adem??s de abordar el tema del apoyo y asesoramiento a centros y del departamento de orientaci??n como elemento dinamizador de la atenci??n a la diversidad en los centros de secundaria.

Jerome S. Bruner: la construcció narrativa de la identitat en temps de crisi

Resum de l'entrevista realitzada el 30 de juny de 2005 per Moisès Esteban i Guitart al psicòleg nord americà Jerome S. Bruner (Nova York, 1915). Tot plegat un viatge per la història de la psicologia del s. XX i principis del s. XXI

Disseny i construcció d’ un braç de robot de 5 graus de llibertat governat des de PC via USB.

El braç robot es va crear com a resposta a una necessitat de fabricació d’elements mitjançant la producció en cadena i en tasques que necessiten precisió. Hi ha, però, altres tipus de tasques les quals no són repetitives, ni poden ésser programades, que necessiten però ser controlades en tot moment per un ésser humà. Són activitats que han d’estar realitzades per un ésser humà, però que requereixen molta precisió, és per això que es creu necessari el disseny d’un prototipus de control d’un braç robot estàndard, que permeti a una persona el control total sobre aquest en temps real per a la realització d’una tasca no repetitiva i no programable prèviament. Pretenem, en el present projecte, dissenyar i construir un braç robot de 5 graus de llibertat, controlat des d’un PC mitjançant un microcontrolador PIC amb comunicació a través d’un bus USB. El robot serà governat des d’un PC a través d’un software de control específic

Disseny i projecte per a la construcció d’una màquina per a realitzar el tall a les castanyes

L’objecte del present projecte es el de realitzar el disseny per a la construcció d’una màquina per fer el tall de castanyes. Aquesta maquina inclourà la estructura, tolva d’alimentació, mecanisme de tall i sistema de seguretat. Un cop realitzat el tall a la castanya, aquesta serà evacuada per gravetat. L’alimentació dins la tolva i l’extracció del producte tallat es realitzarà manualment

Construcci??n y uso de evidencias en torno al r??o : estudio de casos

Seleccionado en la convocatoria: Concurso de proyectos de cooperaci??n en materia de investigaci??n entre departamentos universitarios y departamentos de Institutos de Educaci??n Secundaria o equipos de personal docente, Gobierno de Arag??n 2009-10

La construcci??n del Espacio Europeo de Educaci??n Superior : entre el reto y la resistencia

Resumen tomado de la publicaci??n

Projecte de construcció d’una indústria de plats preparats: situació: polígon indústrial de Celrà (Gironès)

El projecte que es presenta, té com a finalitat comprovar la viabilitat econòmica i dimensionar tots els elements necessaris per dur a terme la construcció d'una indústria de plats preparats al polígon industrial de Celrà (Gironès)