Spatial information on the seabed is largely obtained by different methods of hydrographic survey. Autonomous underwater vehicles (AUVs) are agile and generate high-quality survey data. Positional accuracy of AUVs is based on deployment of a combination of satellite positioning sensors and attitude sensors, as well as subsea acoustic positioning, platform, and hydrographic survey sensors. Establishing mathematical models to determine the coordinates and respective propagation of the uncertainties among these sensors is necessary to define the potential applicability of AUV hydrographic surveys. The objective of our study was to develop, evaluate, and apply a propagation algorithm for uncertainties associated with the spatial information generated by AUV hydrographic surveys. The results show that the critical components of the propagation model are the acoustic positioning performed via ultrashort baseline (USBL). Selection of the correct configuration of sensors and equipment can ensure that AUV hydrographic surveys meet the International Hydrographic Organization’s (IHO’s) specifications for total horizontal uncertainty (THU) associated with the precision required for minimum standards for hydrographic surveys.

The physical habitat simulation sub-routine of the Instream Flow Incremental Methodology (IFIM) uses hydraulic modeling and suitability indices of target fish species to predict how differences in-stream flows affect the microhabitat occupation by fish species. This habitat modelling approach was adopted to assess the ecological effects of running flows on three neotropical fish species of different orders (Bryconamericus ornaticeps , Ancistrus multispinis and Geophagus brasiliensis ).The study encompassed two reaches of an Atlantic Forest stream in Southeastern Brazil where topographic and hydraulic (depth, velocity and type of substrate) characteristics were measured to implement one-dimensional hydraulic simulation. Sub aquatic observation of fish was performed to collect data on microhabitat use and these data were used to develop habitat suitability curves that were used in the habitat simulation to obtain the habitat suitability index (HSI) and weighted usable area (WUA) versus flow curves. Upon these curves minimum and optimum environmental flows for the target fish species were proposed. Bryconamericus ornaticeps and A. multispinis selected microhabitats around 0.6 m depth, whereas G. brasiliensis showed a wider suitable range (0.35-0.9 m). All the three species were mainly observed in microhabitat with low flow velocity (0.1 m/s). Bryconamericus ornaticeps selected more frequently coarse substrate (e.g. boulders) but it appeared also over sandy substrate, whereas A. multispinis and G. brasiliensis selected preferably boulders. The range of 0.65-0.85 m³/s was found as the optimum to meet the needs of the three fish species. Our results agree with the necessary objective information to perform grounded management actions in the frame of a management program aiming at ecosystem conservation. Thereby it can be considered a successful pilot study in environmental flow assessment in an Atlantic Forest stream of Brazil.

Synthetic Aperture Sonar (SAS) is a sensor that was designed for hydrographic survey of the seabed. It detects small targets, enabling high geometric resolution images. However, the images generated by SAS are susceptible to speckle noise, which makes digital processing difficult, since the noises are confused with the targets of interest. The goal of this study was to develop a semi-automatic routine for SAS image processing to verify the structural integrity of submarine pipelines. The method presented incorporates four stages: pre-processing to reduce noise and highlight the targets of interest; extraction of features aiming to recognize features related to the pipelines; post-processing to reduce the fragmentation generated during feature extraction; validation to quantify the results from the reference images to estimate the performance of the proposed methodology. The results showed that more than 80% of the submarine pipelines were mapped in the semi-automatic mode, which considerably reduced the time needed to manually identify a large number of pipelines operating on offshore oilfields.

Os veículos autônomos subaquáticos (AUV) junto a sensores de mapeamento hidrográfico, contribuem na visualização e análise das feições do fundo marinho para diversas finalidades. O volume de dados obtidos no processamento em levantamento hidrográfico, é uma problemática. Desta forma, o projeto objetiva o desenvolvimento de um website acadêmico aplicando a linguagem de programação PHP, com a finalidade de avaliar qualidade posicional das coordenadas obtidas em levantamento hidrográfico com AUV, expondo resultados mais precisos para os valores de incertezas posicionais e a qualidade posicional. O planejamento do projeto foi segmentado por etapas de: análise do algoritmo e desenvolvimento do mesmo na linguagem de programação PHP; para o design foi utilizado a linguagem Cascading Style Sheets (CSS); e correções de eventuais erros no desenvolvimento do projeto. Como resultado, a utilização do site em diversos navegadores, por meio de desktop, não apresentou nenhuma problemática em seu funcionamento. Porém, algo a ser revisado é a formatação de um layout que se ajuste a diferentes em smartphones.