Multibeam sonar systems are much more efficient than the convectional single-beam echo sounders for seafloor-mapping in hydrographic surveying. On the other hand, the operation of multibeam sonar systems needs to integrate more auxiliary sensor units. Because the world coordinates of each footprint is calculated based on the geometry of the sonar head relative to the GPS of the ship. Therefore, the resulting survey quality highly depends on the accuracy of the estimated mounting configuration of the sonar head, and other sensor units. Basically, the configuration parameters include the three Euler's angles, three linear translations and the asynchronous latency of signals between the transducer and other sensors. These parameters can not be measured directly. They can only be estimated from the post-process of the bathymetry data called patch test. Generally, the patch test requires the survey ship to follow several designated paths which are parallel, reciprocal or perpendicular to each other. Furthermore, the choice of seabed slope is also an important factor for the quality of the result. The contour plots of the seabed for the different paths are used to estimate the mounting configuration of the sonar head. In this work, we propose best-fitting a small flat patch to represent the seabed right beneath a segment of the path. A pair of patches from the two adjacent segments of reciprocal or perpendicular paths are selected for comparison. The difference between the two patches gives us an idea how the mounting parameters, i.e. the rolling, pitching and yawing angles, might be. If the parameters are accurately estimated, the two patches should be co-plane. We design several semi-positive definite functions and feed back control algorithms to steer the mounting angles to search for the solutions. One more advantage of this approach is that the variation of each mounting angles as the survey undergoes can be monitored. We test this idea with simulated seabed data, and field data as well. The result is within 1\% difference compared with respect to the angles calibrated by commercial software, such as Hypack.

[pt] Uma relação direta onde a vida em fadiga Número de ciclos por falha pode ser descrita como função das amplitudes macroscópicas de tensão normal e cisalhante, Amplitude de tensão normal macroscópica e Amplitude macroscópica da tensão de cisalhamento, é obtida. Utilizando o critério de Carpinteri e Spagnoli (CeS) como uma ferramenta de inspeção, foram obtidas curvas de nível elípticas sobre um domínio Amplitude de tensão normal macroscópica x Amplitude macroscópica da tensão de cisalhamento. A expressão das curvas de nível obtidas foi generalizada, proporcionando uma ferramenta capaz de prever o número de ciclos para falha associado a qualquer combinação (Amplitude de tensão normal macroscópica, Amplitude macroscópica da tensão de cisalhamento). As previsões obtidas através do método da curva elíptica foram comparadas às observações experimentais, bem como a previsões obtidas a partir de versões adaptadas de modelos consagrados na literatura, a saber: Findley (F), Matake (M), McDiarmid (McD), Susmel e Lazzarin (SeL), Carpinteri e Spagnoli (CeS) e Papadopoulos (P). O modelo proposto forneceu previsões em boa concordância com as observações experimentais, e sua capacidade de avaliar o comportamento em fadiga se revelou o melhor dentro todos os critérios considerados. Por fim, uma leve tendência conservadora do modelo foi atenuada através da introdução de um parâmetro de ajuste, melhorando ainda mais sua capacidade de avaliação de comportamento em fadiga. / [en] A direct relation where fatigue life Number of cycles to failure can be determined as function of macroscopic normal and shear stress amplitudes Macroscopic normal stress amplitude and Macroscopic shear stress amplitude is established. Using the Carpinteri and Spagnoli (CandS) criterion as a survey tool, elliptical level curves in the Macroscopic normal stress amplitude x Macroscopic shear stress amplitude domain were revealed and further generalised, providing means to determine the number of cycles to failure for any given (Macroscopic normal stress amplitude, Macroscopic shear stress amplitude ) combination. Predictions obtained through the elliptical curve method (E) were compared to experimental observations, as well as to predictions obtained from adapted versions of popular fatigue criteria, namely Findley (F), Matake (M), McDiarmid (McD), Susmel and Lazzarin (SandL), Carpinteri and Spagnoli (CandS) and Papadopoulos (P). The proposed model delivered predictions in fair agreement with experimental observations and its predictive capability was seen to be the best among all the considered criteria. Finally, a slight bias towards conservativeness was attenuated with the introduction of an adjusting parameter, further improving the predictive capability of the model.