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ABSTRACT: The autonomous underwater vehicle has proven to be an important tool for study of the seafloor. Detailed seafloor analysis often requires wide area observations with high resolution information. Certain sensors require close proximity to the seafloor or contact, with stable footing to perform integrated measurements over a period of time. Such wide area high resolution surveys cannot be performed by a cruising or hovering type vehicle alone. In this research the authors propose a new class of AUV along with a survey technique in which an underwater vehicle can generate meter order resolution wide area maps of the seafloor, but at intermediate locations, obtain higher, centimeter order resolution information by lowering scanning speed and altitude and finally, by landing to obtain micrometer order resolution measurements or to perform integrated measurements at the same position. A new underwater vehicle with slight negative buoyancy has been developed which has hardware and software to perform landing on the seafloor. Since the seafloor can change abruptly and at short intervals, the reliability and functioning of such technology requires real-time seafloor classification for detection of suitable landing sites. A landing algorithm has been developed which uses laser profile data to calculate a landing vector coordinate for safe landing in realtime and this has been implemented on a newly developed landing vehicle. An autonomous landing system has been developed which uses this algorithm to perform landing operations. Experiments were conducted at a tank facility to demonstrate real-time computation of the landing algorithm and autonomous landing of the vehicle using the proposed system. Results from the landing experiments conducted are presented in this paper.
OCEANS 2011; 01/2011
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ABSTRACT: There are several approaches for 3 dimensional mapping of the seafloor in the actual colours, many of which require multiple cameras, elaborate algorithms and specially designed vehicles. In this paper a method is presented, which uses minimal equipment and simple algorithms for this task, while treating the data in a fully 3 dimensional way from input to output. Because of the reduced hardware demands, it is well suited for combined missions, where the underwater vehicle records some other data as primary task and the map created with the proposed method acts as a support for visualising that data and the environment where it was collected.
OCEANS 2010; 10/2010
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ABSTRACT: Real-time accurate localization is essential for in many underwater vehicle applications. In particular, close-range seafloor observation requires precise positioning in relation to bottom structures or to coordinates on a map. This paper proposes a real-time terrain based localization method that realizes robust positioning that does not require any artificial landmarks. The method stochastically determines vehicle's position relative to the map using the Particle Filter method, based on an inertial navigation system (INS) and a profiling sonar mounted on the vehicle. The reference bathymetric map is constructed a prior, either by the vehicle itself, or by other platforms. The proposed method is implemented on the hovering type AUV TUNA-SAND and sea trials were carried out. We succeeded in the real-time localization and verified the performance of the proposed method.
OCEANS 2009 - EUROPE; 06/2009
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ABSTRACT: This paper proposes a navigation scheme for an AUV to perform large-area imaging of seafloors, especially those of vent fields. The method is based on SLAM (simultaneous localization and mapping) using a profiling sonar and passive acoustic landmarks. Since real-time positioning accuracy of the method is high enough for rough photomosaicing, this method enables an efficient survey with a small overlap and is applicable to seafloors with no visual key for matching. As well as the positioning method, the navigation scheme contains horizontal and vertical path-planning methods, which adapt the vehicle's path to unprescribed landmarks and rough terrains. The method was implemented in the AUV Tri-Dog 1 and a series of sea experiments have been carried out at Tagiri vent field, Kagoshima bay in Japan since 2006. In 2007, the AUV succeeded in imaging around 3,000 m<sup>2</sup> of the seafloor and taking micro bathymetry by light sectioning. The relative accuracy of the navigation scheme is estimated to be 0.5 to 1.0 m by comparing photomosaics between dives.
Autonomous Underwater Vehicles, 2008. AUV 2008. IEEE/OES; 11/2008
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ABSTRACT: In this paper, we introduce a newly developed AUV (Autonomous underwater vehicle) "TUNA-SAND"(Terrain- based Underwater Navigable AUV for Seafloor And Natural resources Development) and its exploration of the hydrothermal vent in Kagoshima Bay, Japan carried out on August 2007. TUNA-SAND is a hovering type AUV constructed in March 2007 as a platform for visual investigation of seafloor features.
OCEANS 2008 - MTS/IEEE Kobe Techno-Ocean; 05/2008
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ABSTRACT: Although underwater vent fields are of great scientific interest, accurate visual mapping is difficult because of the presence of bubble plumes that degrade the accuracy of conventional acoustic positioning systems such as long base line (LBL) and super short base line (SSBL). The authors had proposed a visual mapping method of shallow vent fields with an autonomous underwater vehicle (AUV) equipped with a profiling sonar, where positioning is based on vertical rod-shaped acoustic reflectors and bubble plumes. Although performance was verified through a series of experiments, there remain two challenges as follows. Firstly, observation is terminated if the vehicle was surrounded by bubble plumes, since the vehicle tries to avoid collision with not only artificial reflectors but also collision-safe bubble plumes. Secondly, the observation area drifts by disturbance since the waypoints are defined relative to the vehicle's position after descending close to seafloor. This paper proposes a real-time path planning method of an AUV as a part of the proposed observation method. The path of the vehicle is defined based on the types of landmarks as well as the geometric relationship between the vehicle and the landmarks. The vehicle can distinguish landmark types using a sheet laser and a camera. The proposed method was implemented on the AUV Tri-Dog 1 and a series of experiments were carried out in order to verify its performance.
OCEANS 2007; 11/2007
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T. Inoue,
T. Ura,
H. Sugimatsu, T. Sakamaki,
J. Kojima,
R. Bahl,
S. Panda,
M. Khan,
B.K. Behera,
S.K. Behera,
H. Takahashi,
S. Kar,
C. Kar
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ABSTRACT: The authors have developed a passive acoustic observation system to monitor Irrawaddy dolphins ( Orcaella brevirostris ) in Chilika lagoon. The system is designed to monitor the detailed underwater behavior of dolphins using a Short Base Line (SBL) system all through the day and night. The underwater sounds are recorded at a sampling frequency of 500 kHz with 16 bits resolution. This system was deployed in Chilika lagoon from 29th January to 3rd February and on 18th February in 2007. Experiments were carried out all through the night. By replacing the batteries and hard disks, the observation system was made to keep running all the time. Consequently, the authors succeeded in obtaining click data from Irrawaddy dolphins for a continuous duration of about 21-hour consecutively for each trial and about 1TB of acoustic data was obtained in total. The data contained many high frequency signals, which are considered to be the snapping noise made by shrimp, which are typically found in warm shallow water areas such as Chilika lagoon. A de-noise calculation is developed and applied to the obtained data. A clear picture of trajectories of dolphins in the turbid environment of the Chilika lagoon can be observed that has never before been seen. In this paper, detailed ideas and descriptions of the set up and deployment of the system are presented. Furthermore, the de-noise calculation and the observed dolphin trajectories will be discussed.
OCEANS 2007; 11/2007
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ABSTRACT: Although underwater vent fields are of great scientific interest, little is understood concerning their influence on the underwater ecosystem due to the great difficulties involved in their underwater survey. The authors propose an underwater survey method using AUVs. In previous works, the authors proposed a practical method to survey the "Tagiri" vent area in Kagoshima, in southern Japan [1] [2], and carried out experiments. The field experiments in Tagiri were at some degree successful, but the system also encountered some difficulties. One of the problems was that the AUV could not identify the type of landmarks used to support accurate positioning. In this paper, we propose an autonomous recognition method of bubble plumes using a sheet laser and a camera by image processing. The performance of the proposed method was verified with data obtained in tank experiments, and then implemented in the AUV Tri-Dog 1. Using the proposed method, Tri-Dog 1 performed seafloor observations of the Tagiri vent area in March 2007. Tri-Dog 1 succeeded in distinguishing between bubble plumes and artificial acoustic reflectors, and localizing itself with sufficient accuracy to create a vast, high resolution visual map of the area.
OCEANS 2007; 11/2007
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ABSTRACT: Real-time accurate positioning is a key technology for autonomous underwater vehicles to perform close-range seafloor observations such as photo mosaicing. This paper proposes a real-time positioning method that realizes robust and drift-free positioning in a local area based on a passive acoustic landmarks set in the environment and a profiling sonar (profiler) mounted on the vehicle. The method stochastically updates the vehicle's position based on all the sensory data available. Although the position of landmarks is generally unknown, this paper assumes the position is known without error for simplification. As an observation model of the profiler we propose a radial-angular representation with a non-Gaussian distribution based on experimental data. The performance of the proposed method is verified through tank experiments using the AUV Tri-Dog 1. The effects of the number of landmarks and observation model on the positioning accuracy is discussed. Through comparison with ground truth and off-line estimations based on actual data obtained during the experiments, the positioning accuracy of the proposed method remains within 5 centimeters at all times during the 2 hour duration of the experiment with a traveled distance of 600 meters, with two landmarks at a distance of 10 meters.
OCEANS 2007 - Europe; 07/2007
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T. Ura,
K. Tamaki,
A. Asada,
K. Okamura,
K. Nagahashi, T. Sakamaki,
T. Gamo,
K. Okino,
T. Obara,
K. Nakane,
T. Obata,
Y. Ooyabu,
N. Yamaoka,
Y. Orihashi,
Jun Han,
H. Koyama,
H. Sugimatsu
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ABSTRACT: The autonomous underwater vehicle "r2D4", constructed in 2003, is a cruising type AUV weighing 1,600 kgf with a length of 4.4 m. It is fitted with a side scanning sonar, an interferometry sonar, a CTDO, and an in-site chemical analyzer "GAMOS" for measurement of manganese concentration. The AUV "r2D4" has been deployed off Sado-ga-shima Island along a fault line in the Sea of Japan (2003), over Kuroshima Knoll (2003), North West Rota 1 Underwater Volcano (2004) where it took video images of plumes, and Myojin-sho Underwater Crater (2005), and demonstrated its high performance in autonomy and reliability in hostile environments. During NH06-4 Leg 3 cruise in December 2006, we deployed "r2D4" in the rift valley of Segments 15 and 16 of the Central Indian Mid-Ocean Ridge System. The first area "r2D4" surveyed is "Roger Plateau (tentative name)" at 19 34S, 65 51E. The AUV "r2D4" performed three separate dives and found some anomalies in the concentration of manganese, but we could not identify the location of the origin of these anomalies. The second area is a narrow gorge in the middle of segment 16. The AUV"r2D4" descended to the east peak of the rift valley, with a depth of 2,400 m, near the center of the gorge. After calibration of its magnetometer, the AUV jumped off the cliff to the bottom of 2,700 m deep gorge. The AUV "r2D4" cruised over the bottom of the gorge for about 6 hours at 3.3 knots and took side scan images of the bottom surface covering 25 km<sup>2</sup>. The images show that there is a flat wide lava plain, which is 26 km in length and has an average width of 2.7 km, i.e. 70 km<sup>2</sup> in area. At the north part of the plain, there is a small rock mound. When "r2D4" passed over the rocks, it found significant anomalies in the concentration of manganese and turbidity. Based on the results of the following Tow-yo survey, we came up with a conclusion that there is hydro-thermal activity at this location. It is concluded that based on a carefully-des-
igned navigation plan the cruising type AUV can be a powerful tool for survey of mid-ocean ridge systems with complicated bottom topography.
OCEANS 2007 - Europe; 07/2007
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R. Bahl,
T. Ura,
H. Sugimatsu,
T. Inoue, T. Sakamaki,
J. Kojima,
T. Akamatsu,
H. Takahashi,
S.K. Behera,
A.K. Pattnaik,
M. Khan,
S.K. Kar
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ABSTRACT: Irrawaddy dolphins (Orcaella brevirostris) being on top of the food chain are considered as a flagship species of Chilika. These cetaceans produce characteristic echolocation pulses that make them acoustically visible, night or day. Acoustic-based survey methods are found to be indispensable for surveying porpoises and dolphins in coastal precincts. This paper reports the first such collaborative attempt in Chilika by applying acoustic survey technology based on the design of an innovative compact and portable acoustic survey device designed for observation of groups of small cetaceans. The acoustic sensor system is housed in a "bird-cage" structure containing 3 hydrophones forming a main linear array, together with two more hydrophones forming a small 3-element triangle array with the central hydrophone, in a plane perpendicular to the linear array axis. It weighs 25 kg and is 3.6 m long, 30 cm in diameter, and can be deployed either vertically or horizontally with buoys and a weight. A high-speed multichannel data acquisition system records the dolphin click sounds from all hydrophones. Signal processing algorithms have been developed for automatic detection and discrimination of echolocation clicks from other underwater sounds, localization of sound sources, and tracking individual animals. The device has previously been tested in vertical mode in a quasi-natural environment with a group of bottlenose dolphins that has confirmed its capability to precisely track several vocalizing animals. The depth of the Chilika lagoon in the dolphin habitat can be as shallow as 1.5 m. Thus, the array has to be deployed in horizontal mode, which enables it to provide very good lateral resolution in the broadside direction. This paper reports the first results of using this array in shallow water conditions. Movements of several Irrawaddy dolphins have been observed very clearly.
OCEANS 2006 - Asia Pacific; 06/2007
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ABSTRACT: Finless porpoise populations in coastal precincts are adversely impacted by human activities that cause water pollution, lack of food and denial of migratory paths. Proper survey and management of their populations has therefore become necessary. Visual-based surveys are very tedious, labor intensive, have limited accuracy, and are strongly subject to visibility conditions. These cetaceans produce characteristic echolocation pulses that make them acoustically visible, night or day. Acoustic-based survey methods are expected to be indispensable for surveying finless porpoises that do not exhibit visually dramatic behavior like the oceanic dolphins and spend most of their time underwater. Passive observation of echolocation clicks on arrays of high frequency hydrophones can simultaneously localize several underwater sound sources as they move around. Since the click characteristics are known to be species-specific, individuals belonging to the same group need to be precisely discriminated on basis of their location and movement pattern alone. This paper reports the results from testing a compact and portable acoustic survey device designed for monitoring underwater behavior of groups finless porpoises. The acoustic sensor system consists of 3 hydrophones forming a main vertical linear array, together with two more hydrophones forming a small 3-element triangle array with the central hydrophone, in a plane perpendicular to the linear array axis. It is housed in a "bird-cage" structure that weighs 25 kg and is 3.6 m tall, 30 cm in diameter, and is deployed vertically with a buoy and a weight. The device has been tested in shallow waters of less than 10 meters depth off-Choshi port on the Pacific coast of Japan. Echolocation pulses from several porpoises were recorded. One feature has been the differences in strength of the click signal observed on the hydrophones in the vertical array that is indicative of a narrow beam pattern of the porpoise. The main challenge in loc-
alization has been to eliminate surface and bottom reflections that inevitably occur in shallow water. In addition, echolocation pulses of some dolphins in the vicinity were also simultaneously recorded. An attempt has been made to segregate the porpoise clicks from those of the dolphins, and then to localize the porpoises. The experiment demonstrates the capability of the device for individually tracking several vocalizing animals. This novel tracking system will be used to survey populations of finless porpoises in coastal precincts.
OCEANS 2006 - Asia Pacific; 06/2007
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ABSTRACT: In August 2005, we succeeded in operating AUV "r2D4", which was constructed in July 2003 as one of fruits of R-Two project, into Myojin-sho underwater Caldera in full autonomous mode. The caldera is located about 800 km in the south of Tokyo, and 8 km in diameter. There is an active underwater volcano Myojin-sho at the Northeastern part of outer rim of caldera, which erupted repeatedly in 1952. The Kuroshio current is usually running over the Caldera, so that current speed around it is sometimes more than 3 knots. It can be said that the diving of human occupied vehicle and remotely operated vehicle into Myojin-sho Caldera is very dangerous due to such hostile environment. The interferometry SONAR captured a clear image of the central cone in the middle of crater, and the in-situ chemical analyzer "GAMOS" detected high concentration of manganese ion which indicates hydro-thermal activity in the crater.
OCEANS 2006 - Asia Pacific; 06/2007
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ABSTRACT: Although underwater vent areas are scientifically important, precise photo mosaicing of them is for the following reasons still a hard task. Firstly, the visible range is limited by the turbid water and floating particles. Secondly, the conventional acoustic positioning is vulnerable to the bubble plumes of the vent areas. In this paper a navigation method of an autonomous underwater vehicle (AUV) for photo mosaicing of shallow vent areas where bubbles are spouting is proposed. Simultaneously, this method estimates the position of the AUV and the landmarks, such as bubble plumes and artificial sonar reflectors. The simultaneous localization and mapping (SLAM) based approach enables drift free, accurate, real-time and independent navigation in a local area, which is suitable for photo mosaicing. The proposed method has been implemented on the testbed AUV "Tri-Dog 1" and a tank experiment has been carried out to verify its performance.
OCEANS 2006 - Asia Pacific; 06/2007
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ABSTRACT: While visual observation is an ideal method for detailed survey of seafloors, it is still difficult for an autonomous underwater vehicle (AUV) to track rugged terrains at low altitudes of ideal 1 to 2 meters. This paper proposes a real-time navigation architecture for hovering class AUVs equipped with perceptional sensors looking forwards, sideways and downward, to operate under such conditions. The method controls vertical motion while placing almost no restrictions on motion in the horizontal plane, achieving high compatibility with existing navigation scheme. The algorithm is a hybrid of sensor and map based approaches where the vehicle continually updates a local geometrical map of hazard areas using its perceptional measurements while performing conventional auto-altitude tracking. If the vehicle enters any of the hazard areas, sensor based control is invoked with depth as the control reference to elevate the AUV until it passes the hazard area. The method was verified through tank experiments using the AUV Tri-Dog 1. The AUV successfully followed a lawn-mower trajectory over a rugged terrain consisting of knolls and slopes while maintaining an extremely low altitude of 1.2 meters.
Underwater Technology and Workshop on Scientific Use of Submarine Cables and Related Technologies, 2007. Symposium on; 05/2007
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ABSTRACT: This paper proposes a navigation scheme of an Autonomous Underwater Vehicle (AUV) for photo mosaicing of a shallow vent area with bubble plumes. While bubble plumes disturb acoustic positioning systems, they can be detected by sonars. So the method takes advantage of the plumes as landmarks using a profiling sonar. By adopting the concept of Simultaneous Localization and Mapping (SLAM), the method achieves drift-free, accurate and independent positioning without using conventional acoustic transponders. The high positioning accuracy enables complete data acquisition, as well as position based mosaicing without relying on pictorial correlations of the photos. Some artificial acoustic reflectors are also deployed to enhance positioning performance. The scheme was implemented to the testbed AUV "Tri-Dog 1" and the performance was verified through sea experiments at Tagiri vent area, Kagoshima Bay in Japan. The AUV succeeded in fully autonomous observation at the challenging environment, to build photo mosaics of more than 300 m of the floor including a tube-worm colony
OCEANS 2006; 10/2006
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ABSTRACT: Based on the successes in development and field operations of AUV "R-One Robot", the Underwater Technology Research Center at the University of Tokyo established a five year project for a next generation long-range cruising type AUV from 2001, an AUV named "r2D4". The primary mission for "r2D4" is a survey of an undersea hydrothermal vent area. Construction of the hardware system as well as the primary software system were completed in July 2003. Special features of "r2D4" are the following: (1) Compact size and lightweight (length overall: 4.4 m, weight: 1,600 kg). (2) Operating max depth 4,000 m. (3) Highly accurate positioning by the combined instrumentation of fiber optic gyroscope and Doppler sonar. (4) "r2D4" has superior recognition ability on the complicated underwater environments transition by multiple sensor. (5) Adaptive path replanning ability for the observation. If the vehicle finds a suspicious place or an object in underwater space, it can regenerate the target path dynamically in order to make this observation. After the observation at Ryotsu Bay in the Sea of Japan and Kurosima knoll off Ishigaki Island, "r2D4" investigated the undersea hydrothermal vents at the area of Mariana Trough in June 2004. We succeeded in the observation of the plume from the undersea hydrothermal vents at NW Rota 1 Underwater Volcano with multiple sensor and still camera. We present the outline of the new AUV "r2D4" and the results of the survey.
Oceans 2005 - Europe; 07/2005
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ABSTRACT: This paper proposes a navigation method for an Autonomous underwater vehicle (AUV) operating around structures whose major configuration given in advance. The method consists of a state estimator and a motion controller, enabling localization in the configuration map as well as following pregiven waypoints without any external help. The state estimator is based on a "particle filter" where the vehicle's state, horizontal position and heading, is stochastically updated in real time using multisensor data. This method was implemented on the AUV "Tri-Dog 1" and experiments were carried out around breakwater caissons at the mouth of Kamaishi bay, Iwate Prefecture in Japan. This is the first time a vehicle has succeeded in fully autonomous observation around breakwater caissons. Mosaics of the foot protection blocks, rock mound and caisson's surface are made from the observed images based on the estimated state of the AUV, to verify the performance of the method.
Oceans 2005 - Europe; 07/2005
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ABSTRACT: It is important to investigate the inside of the hull of a submerged wreck for identifying the accident circumstances and causes. Oil-tanker wrecks usually cause serious damage to natural environment. Periodical inspection is also necessary to protect ocean environment. Although these operations are normally carried out by Remotely Operated Vehicles (ROVs), they require specifically designed support vessels with heavy equipment. Thus, their mobility is inevitably restricted for immediate operation. Therefore, it is expected that the demand for the development of compact and intelligent Autonomous Underwater Vehicles (AUVs) to undertake these complicated missions will increase greatly over the next few years. Since AUV navigation into a semi-closed space is a dangerous operation, the AUV should be aware of its surroundings in real time and make careful path planning based on sensory data. Although acoustic sensors are utilized to survey underwater objects, they are seriously affected by multipath effects in a narrow closed space, and may have poor accuracy and resolution, which are not sufficient for AUV navigation. In this paper, we propose an autonomous navigation and investigation system by stereo vision for surveying closed spaces. The system was implemented in a newly constructed AUV, "Tam-Egg 2", a small size autonomous underwater vehicle, and the vehicle successfully identified the rectangular windows of a model hull placed in an experiment tank, and passed through them without touching the hull.
OCEANS, 2005. Proceedings of MTS/IEEE; 02/2005
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ABSTRACT: Autonomous underwater vehicles (AUVs) are suitable for condition survey of the surface of artificial structures such as pillars and caissons in harbors. This paper introduces a method for AUVs to trace artificial structures using a light-section ranging system. This system acquires the profile of the target objects over a wide area using a sheet laser beam. The vehicle navigates by referencing the principal shape of the structure, and traces its surface while taking video images of it. This ranging system also enables 3D mapping of its surroundings based on high accuracy positioning. The method is implemented on the testbed AUV "Tri-Dog 1" and its performance is verified through tank tests. It is shown that the AUV navigates robustly against small obstacles and floating particles. Precise depth mapping of the tank floor is also carried out using the same system.
Control, Automation, Robotics and Vision Conference, 2004. ICARCV 2004 8th; 01/2005
