91 research outputs found
Underwater optical mapping
Peer Reviewe
Fast underwater color correction using integral images
Underwater image processing has to face the problem of loss of color and contrast that occurs when images are acquired at a certain depth and range. The longer wavelengths of sunlight such as red or orange are rapidly absorbed by the water body, while the shorter ones have a higher scattering. Thereby, at larger distance, the scene colors appear bluish-greenish, as well as blurry. The loss of color increases not only vertically through the water column, but also horizontally, so that the subjects further away from the camera appear colorless and indistinguishable, suffering from lack of visible details. This paper presents a fast enhancement method for color correction of underwater images. The method is based on the gray-world assumption applied in the Ruderman-opponent color space and is able to cope with non-uniformly illuminated scenes. Integral images are exploited by the proposed method to perform fast color correction, taking into account locally changing luminance and chrominance. Due to the low-complexity cost this method is suitable for real-time applications ensuring realistic colors of the objects, more visible details and enhanced visual quality.Peer Reviewe
Towards Omnidirectional Immersion for ROV Teleoperation
[Abstract] The use of omnidirectional cameras underwater is enabling many new and exciting applications in multiple fields. Among them, it will allow Remotely Operated Underwater Vehicles (ROVs) to be piloted directly by means of the images captured by omnidirectional cameras through virtual reality (VR) headsets. This immersive experience will extend the pilotâs spatial awareness and reduce the usual orientation problems during missions. This paper presents this concept and illustrates it with the first experiments for achieving this purpose.This research was supported by the Spanish National Projects ARCHROV (Marine ARChaeology through HROV/AUV cooperation) under the agreement DPI2014-57746-C3-3-R and OMNIUS under the agreement CTM2013-46718-R, the Generalitat de Catalunya through the ACCIO/TecnioSpring program (TECSPR14-1-0050) (to N. Gracias), and "la Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement de la Generalitat de Catalunya" (to J. Bosch)Generalitat de Catalunya; TECSPR14-1-0050https://doi.org/10.17979/spudc.978849749808
Omnidirectional underwater surveying and telepresence
Exploratory dives are traditionally the first step for marine scientists to
acquire information on a previously unknown area of scientific interest. Manned
submersibles have been the platform of choice for such exploration, as they allow
a high level of environmental perception by the scientist on-board, and the ability
to take informed decisions on what to explore next. However, manned submersibles
have extremely high operation costs and provide very limited bottom time. Remotely
operated vehicles (ROVs) can partially address these two issues, but have operational
and cost constraints that restrict their usage.
This paper discusses new capabilities to assist scientists operating lightweight hybrid
remotely operated vehicles (HROV) in exploratory missions of mapping and
surveying. The new capabilities, under development within the Spanish National
project OMNIUS, provide a new layer of autonomy for HROVs by exploring three key
concepts: Omni-directional optical sensing for collaborative immersive exploration,
Proximity safety awareness and Online mapping during mission time.Peer Reviewe
Mesure des champs de vitesse dans les champs hydrothermaux océaniques
Nous présentons une nouvelle méthode pour déterminer les champs de vitesse dans les champs hydrothermaux présents sur les fonds sous-marins. Basée sur le "background-oriented schlieren", la méthode permet de suivre les anomalies d'indice de réfraction dues à la température ou la composition. Elle a été testée sur des panaches thermiques en laboratoire, puis lors d'une campagne sur la dorsale atlantique
Quantifying diffuse and discrete venting at the Tour Eiffel vent site, Lucky Strike hydrothermal field
Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 13 (2012): Q04008, doi:10.1029/2011GC003991.The relative heat carried by diffuse versus discrete venting of hydrothermal fluids at mid-ocean ridges is poorly constrained and likely varies among vent sites. Estimates of the proportion of heat carried by diffuse flow range from 0% to 100% of the total axial heat flux. Here, we present an approach that integrates imagery, video, and temperature measurements to accurately estimate this partitioning at a single vent site, Tour Eiffel in the Lucky Strike hydrothermal field along the Mid-Atlantic Ridge. Fluid temperatures, photographic mosaics of the vent site, and video sequences of fluid flow were acquired during the Bathyluck'09 cruise (Fall, 2009) and the Momarsat'10 cruise (Summer, 2010) to the Lucky Strike hydrothermal field by the ROV Victor6000 aboard the French research vessel the âPourquoi Pasâ? (IFREMER, France). We use two optical methods to calculate the velocities of imaged hydrothermal fluids: (1) for diffuse venting, Diffuse Flow Velocimetry tracks the displacement of refractive index anomalies through time, and (2) for discrete jets, Particle Image Velocimetry tracks eddies by cross-correlation of pixel intensities between subsequent images. To circumvent video blurring associated with rapid velocities at vent orifices, exit velocities at discrete vents are calculated from the best fit of the observed velocity field to a model of a steady state turbulent plume where we vary the model vent radius and fluid exit velocity. Our results yield vertical velocities of diffuse effluent between 0.9 cm sâ1 and 11.1 cm sâ1 for fluid temperatures between 3°C and 33.5°C above that of ambient seawater, and exit velocities of discrete jets between 22 cm sâ1 and 119 cm sâ1 for fluid temperatures between 200°C and 301°C above ambient seawater. Using the calculated fluid velocities, temperature measurements, and photo mosaics of the actively venting areas, we calculate a heat flux due to diffuse venting from thin fractures of 3.15 ± 2.22 MW, discrete venting of 1.07 ± 0.66 MW, and, by incorporating previous estimates of diffuse heat flux density from Tour Eiffel, diffuse flux from the main sulfide mound of âŒ15.6 MW. We estimate that the total integrated heat flux from the Tour Eiffel site is 19.82 ± 2.88 MW and that the ratio of diffuse to discrete heat flux is âŒ18. We discuss the implication of these results for the characterization of different vent sites within Lucky Strike and in the context of a compilation of all available measurements of the ratio of diffuse to discrete heat flux.E. Mittelstaedt was supported
by the International Research Fellowship Program of the U.S.
National Science Foundation (OISE-0757920). Funding for the
2006, 2008, 2009, and 2010 cruises was provided by CNRS/
IFREMER through the MoMAR program (France), by ANR
(France), the Mothseim Project NT05â3 42213 to J. EscartĂn
and by grant CTM2010â15216/MAR from the Spanish Ministry
of Science to R. Garcia and J. EscartĂn. T. Barreyre was supported
by University Paris Diderot (Paris 7 â France) and
Institut de Physique du Globe de Paris (IPGP, France).2012-10-1
Hydrothermal activity along the slow-spreading Lucky Strike ridge segment (Mid-Atlantic Ridge) : distribution, heatflux, and geological controls
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 431 (2015): 1730185, doi:10.1016/j.epsl.2015.09.025.We have reviewed available visual information from the seafloor, and recently acquired
microbathymetry for several traverses across the Lucky Strike segment, to evaluate the
distribution of hydrothermal activity. We have identified a new on-axis site with diffuse
flow, Ewan, and anactive vent structure ~1.2 km from the axis, Capelinhos. These sites
are minor relative to the Main field, and our total heatflux estimate for all active sites
(200-1200 MW) is only slightly higher than previously published estimates. We also
identify fossil sites W of the main Lucky Strike field. A circular feature ~200 m in
diameter located on the flanks of a rifted off-axis central volcano, is likely a large and
inactive hydrothermal edifice, named Grunnus. We find no indicator of focused
hydrothermal activity elsewhere along the segment, suggesting that the enhanced melt
supply and the associated melt lenses, required to form central volcanoes, also sustain
hydrothermal circulation to form and maintain large and long-lived hydrothermal fields.
Hydrothermal discharge to the seafloor occurs along fault traces, suggesting focusing of
hydrothermal circulation in the shallow crust along permeable fault zones.This work has been partly financed by ANR (France) Mothseim
Project NT05-3 42213 toJE, and by EU-RTN-MOMARNET to MC. The French Ministry of
Research financed ship, ROV and AUV time (Graviluckâ06, MOMARâ08, Bathyluckâ09,
MOMARSAT cruises in 2010-2015
Autonomous underwater navigation and optical mapping in unknown natural environments
We present an approach for navigating in unknown environments while, simultaneously, gathering information for inspecting underwater structures using an autonomous underwater vehicle (AUV). To accomplish this, we first use our pipeline for mapping and planning collision-free paths online, which endows an AUV with the capability to autonomously acquire optical data in close proximity. With that information, we then propose a reconstruction pipeline to create a photo-realistic textured 3D model of the inspected area. These 3D models are also of particular interest to other fields of study in marine sciences, since they can serve as base maps for environmental monitoring, thus allowing change detection of biological communities and their environment over time. Finally, we evaluate our approach using the Sparus II, a torpedo-shaped AUV, conducting inspection missions in a challenging, real-world and natural scenario
Reconfigurable AUV for Intervention Missions: A Case Study on Underwater Object Recovery
Starting in January 2009, the RAUVI (Reconfigurable Autonomous Underwater Vehicle for Intervention Missions) project is a 3-year coordinated research action funded by the Spanish Ministry of Research and Innovation. In this paper, the state of progress after 2 years of continuous research is reported. As a first experimental validation of the complete system, a search and recovery problem is addressed, consisting of finding and recovering a flight data recorder placed at an unknown position at the bottom of a water tank. An overview of the techniques used to successfully solve the problem in an autonomous way is provided. The obtained results are very promising and are the first step toward the final test in shallow water at the end of 2011
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