Autonomous underwater vehicle (AUV) navigation has been a challenging problem for a long time. Navigation is challenging due to the drift present in underwater environments and the lack of precise localisation systems such as GPS. Therefore, the uncertainty of the vehicle’s pose grows with the mission’s duration. This research investigates methods to form constraints on the vehicle’s pose throughout typical surveys. Current underwater navigation relies on acoustic sensors. Side Scan Sonar (SSS) is cheaper than Multibeam echosounder (MBES) but can generate 2D intensity images of wide sections of the seafloor instead of 3D representations. The methodology consists in extracting information from pairs of side-scan sonar images representing overlapping portions of the seafloor and computing the sensor pose transformation between the two reference frames of the image to generate constraints on the pose. The chosen approach relies on optimisation methods within a Simultaneous Localisation and Mapping (SLAM) framework to directly correct the trajectory and provide the best estimate of the AUV pose. I tested the optimisation system on simulated data to evaluate the proof of concept. Lastly, as an experiment trial, I tested the implementation on an annotated dataset containing overlapping side-scan sonar images provided by SMaRC. The simulated results indicate that AUV pose error can be reduced by optimisation, even with various noise levels in the measurements. / Navigering av autonoma undervattensfordon (AUV) har länge varit ett utmanande problem. Navigering är en utmaning på grund av den drift som förekommer i undervattensmiljöer och bristen på exakta lokaliseringssystem som GPS. Därför ökar osäkerheten i fråga om fordonets position med uppdragets längd. I denna forskning undersöks metoder för att skapa begränsningar för fordonets position under typiska undersökningar. Nuvarande undervattensnavigering bygger på akustiska sensorer. Side Scan Sonar (SSS) är billigare än Multibeam echosounder (MBES) men kan generera 2D-intensitetsbilder av stora delar av havsbotten i stället för 3D-bilder. Metoden består i att extrahera information från par av side-scan sonarbilder som representerar överlappande delar av havsbotten och beräkna sensorns posetransformation mellan bildens två referensramar för att generera begränsningar för poset. Det valda tillvägagångssättet bygger på optimeringsmetoder inom en SLAM-ram (Simultaneous Localisation and Mapping) för att direkt korrigera banan och ge den bästa uppskattningen av AUV:s position. Jag testade optimeringssystemet på simulerade data för att utvärdera konceptet. Slutligen testade jag genomförandet på ett annoterat dataset med överlappande side-scan sonarbilder från SMaRC. De simulerade resultaten visar att AUV:s poseringsfel kan minskas genom optimering, även med olika brusnivåer i mätningarna.

Natural hydrocarbon seeps harbor distinctive geological, chemical, and biological features in the marine environment. This thesis verified remote sensing signatures of seeps using in-situ observation and repeated collections of satellite imagery. Bubble streams in the Gulf of Mexico water column from four natural seep sites on the upper continental slope were imaged by a side-scan sonar, which was operated from a submarine near the seafloor, and by acoustic profilers, which were operated from surface ships. These data were correlated with sea surface slicks imaged by Synthetic Aperture Radar (SAR) on the RADARSAT satellite. Comparing non-oily bubble streams from rapidly venting mud volcanoes with oily bubble streams from shallow deposits of gas hydrate showed that they produced notably different signatures. Non-oily bubbles produced high backscatter on the side-scan sonar records, but were difficult to detect with the acoustic profilers. Oily bubbles from hydrate deposits produced acoustic shadows on the side-scan sonar records. The oily bubbles generated clear signatures extending from the seafloor to the near surface on the acoustic profile records. RADARSAT SAR images verified the presence of surface oil slicks over the hydrate deposits, but not over the mud volcanoes. This indicates that SAR imagery will not be able to capture every oil and gas seep in a region because non-oily bubble streams do not create surface oil slicks. A total of 113 natural oily seep sources were identified based on surface slicks in eleven SAR images collected over the northern continental slope. A persistence analysis verified that SAR is a dependable tool for capturing oil slicks because 93.5% of the slick sources identified in the 2001 images were corroborated with slicks in the 2002 images. The sources ranged in depth from 100 to 2000 m and 79% of the sources were in 900 meters or greater of water. Seventy-six percent of the seep sources were associated with salt less than 1500 m below the seafloor and none of the sources were located in the bottom of salt withdrawal basins. Geographical Information Systems (GIS) proved to be a useful tool in these analyses.

Abstract The interpretation and identification of information from the side-scan sonar imagery are mainly depended on visual observation and personal experiences. Recent studies tended to increase the identification efficiency by using numerical analysis methods. This can reduce the error that cause by the differences of observer¡¦s experience as well as by extended time observation. The position around the center line of the slant range corrected side-scan sonar imagery might result in the degradation of the ability of numerical methods to successfully detect artificial objects. Theoretically, this problem could be solved by using a specific characteristic function to identify the existence of concrete reefs, and then filtering the noise of the central line area with a threshold value. This study was intended to develop fully automatic sonar imagery processing system for the identification of cubic concrete and cross-type protective artificial reefs in Taiwan offshore area. The procedures of the automatic sonar imagery processing system are as follows: (1) Image Acquisition¡G500kHz with slant range of 75m. (2) Feature Extraction¡Ggrey level co-occurrence matrix (i.e., Entropy, Homogeneity and Mean) (3) Classification¡Gunsupervised Bayesian classifier. (4) Object Identification¡Gby characteristic feature (i.e., Entropy). (5) Object¡¦s Status Analysis¡Gobject¡¦s circumference¡Barea¡Bcenter of mass and quantity. This study used the sonar images collected at Chey-Ding artificial reef site in Kaohsiung City as a case study, aiming to verify the automatic sonar imagery processing system and find out the optimum window size. The image characteristic functions include one set of first order parameter (i.e., mean) and two sets of second order parameter (i.e., entropy and homogeneity). Eight(8) sonar images with 1-8 sets of cubic concrete and cross-type protective artificial reefs where used in this step. The identification efficiency of the system, in terms of the produce¡¦s accuracy, is 79.41%. The results illustrated that there were 16~28 sets of artificial reefs being detected in this case which is comparable with the actual amount of 17 sets. Based on this investigation, the optimum window size was concluded to be 12¡Ñ12 pixels with sliding size of 4 pixel. Imagery collected at Fang-Liau artificial reef site of Pingtung County was tested. For the purpose of applicability, the original imagery (2048¡Ñ2800 pixels) was divided into 8 consecutive smaller sized imagery frames(2048¡Ñ350 pixels). The influence of using a two-fold classification procedure and a central filtering method to reduce the noise that caused by slant range correction were discussed. The results showed that central line filtering method is applicable. The results of object¡¦s status analysis showed that there are 156-236 sets of reefs existed. Automatic determination of the target using the characteristic function of entropy is feasible. If the value is larger than 1.45, it represents positive identification of concrete artificial reefs. It can be classified as muddy sand seabed type if the value is smaller than 1.35. If the value is between 1.35~1.45, it illustrates the existence of a transition zone where objects of smaller in dimensions might exist. To achieve the purpose of automatic operation, firstly, we have to identify the existence of the concrete reefs by using the specific characteristic function. Based on the result of existing concrete reefs, suture line filtering method will hence be used to filter the noise from the image information. For that all of the procedures are automatically operated without human intervention. Key word: side-scan sonar ; characteristic function ; gray level co-occurrence matrix ; Bayesian classification ;entropy ; homogeneity ; mean

Natural hydrocarbon seeps harbor distinctive geological, chemical, and biological features in the marine environment. This thesis verified remote sensing signatures of seeps using in-situ observation and repeated collections of satellite imagery. Bubble streams in the Gulf of Mexico water column from four natural seep sites on the upper continental slope were imaged by a side-scan sonar, which was operated from a submarine near the seafloor, and by acoustic profilers, which were operated from surface ships. These data were correlated with sea surface slicks imaged by Synthetic Aperture Radar (SAR) on the RADARSAT satellite. Comparing non-oily bubble streams from rapidly venting mud volcanoes with oily bubble streams from shallow deposits of gas hydrate showed that they produced notably different signatures. Non-oily bubbles produced high backscatter on the side-scan sonar records, but were difficult to detect with the acoustic profilers. Oily bubbles from hydrate deposits produced acoustic shadows on the side-scan sonar records. The oily bubbles generated clear signatures extending from the seafloor to the near surface on the acoustic profile records. RADARSAT SAR images verified the presence of surface oil slicks over the hydrate deposits, but not over the mud volcanoes. This indicates that SAR imagery will not be able to capture every oil and gas seep in a region because non-oily bubble streams do not create surface oil slicks. A total of 113 natural oily seep sources were identified based on surface slicks in eleven SAR images collected over the northern continental slope. A persistence analysis verified that SAR is a dependable tool for capturing oil slicks because 93.5% of the slick sources identified in the 2001 images were corroborated with slicks in the 2002 images. The sources ranged in depth from 100 to 2000 m and 79% of the sources were in 900 meters or greater of water. Seventy-six percent of the seep sources were associated with salt less than 1500 m below the seafloor and none of the sources were located in the bottom of salt withdrawal basins. Geographical Information Systems (GIS) proved to be a useful tool in these analyses.

The normal procedure for the detection of underwater stationary targets is mainly by the application of side-scan sonar. In addition, the identification of targets within the side-scan sonar imagery is primarily based on the visual observation of the operator. Due to its complexity and poor effectiveness, the visual observation procedure was gradually been substituted by numerical analysis procedures and programs. The purpose of the current investigation was dedicated to the development of an automatic image analysis program for the detection and identification of cubic concrete artificial reefs (2 m x 2 m x 2m) in the south-western coastal area off Taiwan. The major components and methodologies of the program include: (1)Image acquisition; side-scan sonar at 500 kHz and slant range at 75 m. (2)Feature extraction; grey level co-occurrence matrix. (3)Feature Classification; unsupervised Bayesian classifier. (4)Target identification; cluster analysis. (5)Target properties analysis, includes circumference, area, central coordinates and quantity of the targets. Program verification and optimal parameters determination were conducted with a sonograph (650 ¡Ñ 650 pixels) acquired at the Chey-Ding artificial reef site off Kaohsiung County. Feature functions employed in this program include entropy, homogeneity, and mean value. The identification accuracy can reach 93% at the most. In addition, the number of artificial reefs estimated by the program was within 9 to 20, while the actual number is 15. A realistic evaluation of this program was conducted with a sonograph (2048 ¡Ñ 6050 pixels) acquired at Fang-Liau artificial reef site off Pyngdong County. In addition to the cubic reefs, the targets at this site include cross-shaped artificial reefs with dimensions less than the cubic reefs. The sonograph was divided into smaller blocks with dimensions of 2048 x 550 pixels during evaluation. The results showed that each block can be evaluated based on the value of the seed point obtained by cluster analysis. The seed point which fells between 20.6 and 24.4 indicates that there are cubic reefs existed. Between 15.3 and 17.4 indicates that there are targets with smaller dimensions (i.e., crossed reefs) existed which can not be identified properly. Between 10.1 and 10.9, there is no target existed on the seafloor. The results indicated that the number of targets identified is between 122 and 240. According to the results of this investigation, the automatic image analysis program can improve the detection and identification of stationary targets within side-scan sonar imagery.

The size and organization of bed material, bed texture, is a fundamental attribute of channels and is one component of the physical habitat of aquatic ecosystems. Multiple discipline-specific definitions of texture exist and there is not a universally accepted metric(s) to quantify the spectrum of possible bed textures found in aquatic environments. Moreover, metrics to describe texture are strictly statistical. Recreational-grade side scan sonar systems now offer the possibility of imaging submerged riverbed sediment at resolutions potentially sufficient to identify subtle changes in bed texture with minimal cost,expertise in sonar, or logistical effort. However, inferring riverbed sediment from side scan sonar data is limited because recreational-grade systems were not designed for this purpose and methods to interpret the data have relied on manual and semi-automated routines. Visual interpretation of side scan sonar data is not practically applied to large volumes of data because it is labor intensive and lacks reproducibility. This thesis addresses current limitations associated with visual interpretation with two objectives: 1) objectively quantify side scan sonar imagery texture, and 2) develop an automated texture segmentation algorithm for broad-scale substrate characterization. To address objective 1), I used a time series of imagery collected along a 1.6 km reach of the Colorado River in Marble Canyon, AZ. A statistically based texture analysis was performed on georeferenced side scan sonar imagery to identify objective metrics that could be used to discriminate different sediment types. A Grey Level Co-occurrence Matrix based texture analysis was found to successfully discriminate the textures associated with different sediment types. Texture varies significantly at the scale of ≈ 9 m2 on side scan sonar imagery on a regular 25 cm grid. A minimum of three and maximum of five distinct textures could be observed directly from side scan sonar imagery. To address objective 2), linear least squares and a Gaussian mixture modeling approach were developed and tested. Both sediment classification methods were found to successfully classify heterogeneous riverbeds into homogeneous patches of sand, gravel, and boulders. Gaussian mixture models outperformed the least squares models because they classified gravel with the highest accuracies.Additionally, substrate maps derived from a Gaussian modeling approach were found to be able to better estimate reach averaged proportions of different sediments types when they were compared to similar maps derived from multibeam sonar.

While side-scan sonar has become a valuable geophysical tool for forensic water searches, controlled research is paramount to determine the best practices for searches in aquatic environments as it provides a structured environment in which to investigate variables that influence the effectiveness of the technology and provides valuable experience for sonar operators. The purpose of this research is to conduct controlled research in order to evaluate the applicability of side-scan sonar to searches involving submerged firearms and proxy cadavers. In addition, the best practices for employing this technology in forensic searches in freshwater ponds and lakes in a humid, subtropical environment in Central Florida would be developed. Five street-level firearms were submerged in a pond, and two sets of three pig carcasses (Sus scrofa), utilized as proxies for human bodies, were staked to the bottom of a pond for this research. Transects were conducted over the firearms and the pig carcasses utilizing side-scan sonar. The first set of pig carcasses represented a child size (30-32 kg) and the second set a small adult size (51-54 kg). Results show that firearms were not detected due to the terrain and small size. However, this technology successfully located small to medium-sized proxy carcasses on a flat, sandy lake bottom when experienced operators were conducting the search. Conversely, vegetation obscured submerged bodies. While the smaller carcasses were difficult to detect throughout the data collection, medium-sized carcasses were easily discerned. Moreover, the medium-sized carcasses decomposed at the same rate as previous studies and were visible throughout each stage of decomposition. Finally, employing a 900 kHz frequency with a 20 m swath-width provided the best search parameters. Therefore, in the appropriate conditions, iv side-scan sonar is an effective tool for locating submerged bodies in freshwater lakes and ponds in a humid, subtropical environment.

Η παρούσα εργασία εκπονήθηκε στα πλαίσια του Διατμηματικού Προγράμματος Μεταπτυχιακών σπουδών στις περιβαλλοντικές Επιστήμες. Οι θαλάσσιες γεωφυσικές έρευνες εκτελέστηκαν από το Εργαστήριο Θαλάσσιας Γεωλογίας και Φυσικής Ωκεανογραφίας (Ε.ΘΑ.ΓΕ.Φ.Ω) του Τμήματος Γεωλογίας του Πανεπιστημίου Πατρών. Οι έρευνες του Οκτωβρίου του 2011 αποτελούν συνέχεια αυτών του Οκτωβρίου του 2010 με σκοπό να καλυφθεί το σύνολο της θαλάσσιας περιοχής για την οποία υπάρχει αδειοδότηση. Αντικείμενο της έρευνας είναι η γεωφυσική διασκόπηση του πυθμένα με τη χρήση ηχοβολιστή πλευρικής σάρωσης (side scan sonar) στις περιοχές της Νεάπολης και της Ελαφονήσου με σκοπό: α) την αποτύπωση της μορφολογίας του πυθμένα και β) τον εντοπισμό βιολογικών πόρων (λιβάδια Posidonia oceanica και ασβεστιτικά ροδοφύκη). Τα λιβάδια της Posidonia oceanica και τα ασβεστιτικά ροδοφύκη αποτελούν ενδημικά είδη της Μεσογείου των οποίων ο ρυθμός αύξησής τους θεωρείται εξαιρετικά αργός ενώ παράλληλα ο ρυθμός καταστροφής τους είναι τεράστιος και κρίνεται απαραίτητη η χαρτογράφηση τους ώστε να παρθούν καλύτερα μέτρα προστασίας.Η εμφάνιση των δύο βιολογικών σχηματισμών συμπίπτει με την βιβλιογραφία καθώς για την περιοχή μελέτης της Νεάπολης η Posidonia oceanica εμφανίζεται σε βάθη 0-35 m και στην Ελαφόνησο 0-25 m.Οι σχηματισμοί των ασβεστιτικών ροδοφυκών-ροδόλιθων εμφανίζονται σε βάθη 50-100 m για την Νεάπολη και 20-100 m για την Ελαφόνησο. / This present study was conducted for the Interdepartmental program of postgraduate studies in environmental sciences, Department of Geology. Marine geophysical survey took place in October 2011 by the Laboratory of Marine Geology and Physical Oceanography. The current research follows the survey of October 2010 in order to cover the entire sea area for which license was given. The purpose of this thesis is to have a full bottom analysis for the areas Neapoli and Elafonisos , using side scan sonar, and mapping Posidonia oceanica and Coralligene formations which are two very important species for the marine environment.

Made available in DSpace on 2015-03-13T17:08:34Z (GMT). No. of bitstreams: 1 CamilaHCS_DISSERT.pdf: 5199158 bytes, checksum: 3fe566edfdb484ed92ea990061bd1ccd (MD5) Previous issue date: 2012-02-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The aim of this study was the seasonal characterization of the morphology, sedimentology and hydrodynamic of the A?u, Cavalos and Conchas estuaries. These estuaries are inserted in a semi-arid climate area and form the mouth of the hydrographic basin of the Piranhas-A?u river, that represent the discharge of the largest watershed in the state. They are embedded in an environment consisting of a fluvial-marine floodplain, mangrove ecosystem, sandbanks, fields of dunes, spits and sandy beaches. Adjacent to the natural units are the main local socioeconomic activities (oil industry, salt industry, shrimp farming, fishing and tourism) are dependent on this river and its conservation. The environmental monitoring is necessary because it is an area under constant action of coastal processes and at high risk of oil spill. The acquisition and interpretation of hydrodynamic, sonographic and sediment data was conducted in two campaigns, dry season (2010) and rainy season (2011), using respectively the current profiler ADCP Doppler effect, the side-scan sonar and Van Veen sampler. In these estuaries: A?u, Cavalos and Conchas were identified the following types of bedforms: flatbed and Dunes 2-D and 3-D (small to medium size), generated at lower flow regime (Froude number <1). Structures such as ripples were observed in the A?u estuary mouth. The higher values of flow discharge and velocity were recorded in the A?u estuary (434,992 m?.s-? and 0,554 m.s-?). In rainy season, despite the record of highest values of discharge and flow velocities at the mouth, the energy rates upstream did not differ much from the data of the dry season. However, in all estuaries were recorded an increase in speed and flow, with reservation to the flow in the A?u estuary and flow at the mouth of the Conchas estuary. Sediment grain sizes tend to increase towards the mouth of the estuary and these ranged from very fine sand to very coarse sand, medium sand fraction being the most recurrent. Based on the data acquired and analyzed, the estuaries A?u, Cavalos and Conchas are classified as mixed , dominated by waves and tides. According to their morphology, they are classified as estuaries constructed by bar and according to the classification by salinity, estuaries Conchas and Cavalos were ranked as hypersaline estuaries, and A?u as hypersaline and vertically well mixed type C / Este trabalho teve como objetivo a caracteriza??o sazonal da morfologia, sedimentologia e hidrodin?mica dos estu?rios A?u, Cavalos e Conchas. Estes estu?rios est?o inseridos numa regi?o semi-?rida e comp?e a desembocadura do Rio Piranhas-A?u, maior bacia hidrogr?fica do Estado do Rio Grande do Norte. Compreendem um ambiente constitu?do por plan?cie de inunda??o fl?vio-marinha, ecossistema de manguezal, bancos arenosos, campos de dunas, pontais e praias arenosas, onde os processos costeiros atuantes s?o ressaltados principalmente pela din?mica das modifica??es nas estruturas morfol?gicas ali presentes. Adjacente as unidades naturais, as principais atividades socioecon?micas locais s?o constituidas pela ind?stria petrol?fera, salineira, carcinicultura, pesqueira e tur?stica, tamb?m dependentes deste rio e da sua conserva??o. O monitoramento ambiental desta regi?o se faz portanto necess?rio por se tratar de uma ?rea sob constante a??o dos processos costeiros e com alto risco ao derramamento de ?leo. A aquisi??o de dados hidrodin?micos, sonogr?ficos e sedimentol?gicos foi realizada em duas campanhas: uma no per?odo seco de 2010 e outra no per?odo chuvoso de 2011, utilizando respectivamente, perfilador de correntes por efeito Doppler- ADCP, sonar de varredura lateral e amostrador pontual Van Veen. Nestes estu?rios foram identificadas fei??es de fundo do tipo Leito Plano e Dunas 2-D e 3-D (pequeno a m?dio porte), geradas em regime de fluxo inferior (n?mero de Froude <1). Estruturas do tipo marcas onduladas (ripples) foram observadas somente na foz do estu?rio A?u. Os maiores valores de vaz?o e velocidade do fluxo foram registrados no estu?rio A?u (434,992 m?.s-? e 0,554 m.s-?). No per?odo chuvoso foram registrados os maiores valores de descarga e velocidades do fluxo na regi?o da foz. Entretanto, na montante as taxas de energia n?o diferenciaram muito dos dados obtidos no per?odo seco. Contudo, foi registrado nos tr?s estu?rios um aumento na velocidade e na vaz?o durante o per?odo chuvoso, com ressalva na vaz?o no estu?rio A?u e na vaz?o na foz do estu?rio Conchas. Os sedimentos presentes nos estu?rios variaram de areia muito fina a areia muito grossa, sendo a fra??o areia m?dia a mais recorrente. Em geral a granulometria aumentou em dire??o a foz dos estu?rios. Com base na an?lise e interpreta??o dos dados adquiridos os estu?rios A?u, Cavalos e Conchas foram classificados como dominados por processos misto de ondas e mar?s. De acordo com a morfologia foram classificados como estu?rios constru?dos por barra e segundo a classifica??o por salinidade, os estu?rios A?u, Cavalos e Conchas foram classificados como estu?rios hipersalinos. Adicionalmente o estu?rio A?u tamb?m foi classificado como verticalmente bem misturado do tipo C

Small scale protected zones are valuable for helping the health and productivity of fisheries at Lake Tanganyika (East Africa). Spatial placement of protected areas relies on accurate maps of benthic habitats, consisting of detailed bathymetry data and information on lake-floor substrates. This information is unknown for most of Lake Tanganyika. Fish diversity is known to correlate with rocky substrates in ≤ 30 m water depth, which provide spawning grounds for littoral and pelagic species. These benthic habitats form important targets for protected areas, if they can be precisely located. At the NMVA, echosounding defined the position of the 30-m isobath and side-scan sonar successfully discriminated among crystalline basement, CaCO3-cemented sandstones, mixed sediment, and shell bed substrates. Total area encompassed from the shoreline to 30 m water depth is ~21 km2 and the distance to the 30-m isobath varies with proximity to deltas and rift-related faults. Total benthic area defined by crystalline basement is ~1.6 km2, whereas the total area of CaCO3-cemented sandstone is 0.2 km2. Crystalline basement was present in all water depths (0-30 m), whereas CaCO3-cemented sandstones were usually encountered in water ≤ 5 m deep. Spatial organization of rocky substrates is chiefly controlled by basin structure and lake level history.