Toward autonomous exploration in confined underwater environments

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Journal of Field Robotics 33 (2016): 994-1012, doi:10.1002/rob.21640.In this field note we detail the operations and discuss the results of an experiment conducted in the unstructured environment of an underwater cave complex, using an autonomous underwater vehicle (AUV). For this experiment the AUV was equipped with two acoustic sonar to simultaneously map the caves’ horizontal and vertical surfaces. Although the caves’ spatial complexity required AUV guidance by a diver, this field deployment successfully demonstrates a scan matching algorithm in a simultaneous localization and mapping (SLAM) framework that significantly reduces and bounds the localization error for fully autonomous navigation. These methods are generalizable for AUV exploration in confined underwater environments where surfacing or pre-deployment of localization equipment are not feasible and may provide a useful step toward AUV utilization as a response tool in confined underwater disaster areas.This research work was partially sponsored by the EU FP7-Projects: Tecniospring- Marie Curie (TECSPR13-1-0052), MORPH (FP7-ICT-2011-7-288704), Eurofleets2 (FP7-INF-2012-312762), and the National Science Foundation (OCE-0955674)

Automatic construction of ortophotomaps: a photometric approach

[ES] La construcción de mosaicos de imágenes permite obtener representaciones de grandes dimensiones y resolución de una misma escena. Son frecuentes hoy día las cámaras fotográficas que incorporan un software destinado a su construcción o aplicaciones en línea como Google Maps que permiten visualizar mapas resultantes de la construcción de foto-mosaicos. Habitualmente los mosaicos panorámicos son generados a partir de imágenes adquiridas mediante una cámara que únicamente efectúa movimientos de rotación alrededor de un punto fijo. Cuando las condiciones de adquisición varían y la cámara también se traslada, surgen fenómenos, como el de paralaje, que dificultan la unión no perceptible de las imágenes. A ello hay que añadir las diferencias en apariencia que varias fotografías adyacentes pueden presentar debido a mecanismos automáticos de las cámaras, como el de control de exposición. En el presente trabajo se describe un procedimiento completo para la construcción automática de mosaicos con apariencia totalmente continua y consistente, en los que las uniones de las distintas imágenes que lo conforman no son visibles. Las imágenes son registradas mediante métodos que garantizan consistencia geométrica, y unidas utilizando técnicas de fusión (o blending), con el objetivo de asegurar una transición no visible entre imágenes y una apariencia global coherente en todo el mosaico. El procedimiento descrito es aplicado sobre una secuencia con el fin de evaluar su utilización en el contexto de las imágenes aéreas de grandes dimensiones.[EN] Mosaicing allows to obtain a high-resolution representation of a given scene. Off-the-shelf still cameras including built-in software to build photo-mosaics and online applications such as Google Maps allowing to visualize maps resulting from a photomosaic are common nowadays. In most cases panoramic mosaics are generated from images acquired by means of a camera undergoing uniquely a rotation movement. When the acquisition conditions change, and the camera also performs a translation movement, the parallax phenomenon appears. If parallax exists, the seamless combination of the images is even more challenging. Additionally, adjacent photographs may present differences in appearance due to some automatic camera mechanisms, such as the automatic exposure. In this work a full processing pipeline intended to automatically build seamless mosaics with continuous and consistent appearance is described. Images are joined using methods which guarantee geometrical consistency, and fused using blending techniques, to achieve a non-visible transition between images. The described pipeline is applied on a high-resolution image sequence in order to evaluate its application in the context of aerial images of large dimensions.El trabajo ha sido parcialmente financiado por el MICINN bajo el proyecto CTM2010-15216. Laszl ´ o Neumann ha sido financiado por ICREA de la Generalitat de Catalunya. Las imagenes de las Figuras 2, 4 y 5 son gentileza del Consorcio de l’Estany de BanyolesPrados, R.; García, R.; Neumann, L. (2013). Construcción automática de ortofotomapas: una aproximación fotométrica. Revista Iberoamericana de Automática e Informática industrial. 10(1):104-115. https://doi.org/10.1016/j.riai.2012.11.010OJS104115101Agarwala, A., Dontcheva, M., Agrawala, M., Drucker, S., Colburn, A., Curless, B., Salesin, D., Cohen, M., August 2004. Interactive digital photomontage. In: Proc. SIGGRAPH04.Arévalo, V., & González, J. (2008). An experimental evaluation of non‐rigid registration techniques on Quickbird satellite imagery. 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