No abstract

No abstract

No abstract

Mapping coastal environments is a challenging task, as field surveys and favorable oceanographic conditions are required. Remote sensing offers a practical alternative for extracting depth information, obtaining a fast, repetitive and low-cost mapping over large areas to optimize and minimize field work. This study aims to generate and evaluate Satellite-Derived Bathymetric (SDB) models from Sentinel-2A and 2B images on Praia dos Anjos, Brazil. The log-transform band ratio model was applied in this study. Two images from Sentinel-2 were used, from April 6, 2019 and June 20, 2019. For calibration and validation of SDB, depths were measured in the field with an echosounder on April 4, 2019. Different intervals of depths were tested, and the red wavelength to estimate depths up to 4 m. The statistical correlation between the image and control points on April 6, was r2 = 0.927 for 1-13 m depth interval and between SDB and check points was r2 = 0.893 with a Root Mean Square Error (RMSE) = 1.095. On June 20, the correlation between image and control points was r2 = 0.938 for 1-13 m depth interval, and between SDB and check points was r2 = 0.919 with a RMSE = 0.98. This study showed that remote sensing can be applied to estimate depths on Praia dos Anjos. Bathymetric information is essential for environmental monitoring and coastal engineering works. Further tests in the area are recommended to improve the models and an assessment of the calibrated equations for future applications with new measured check points.

No abstract

As constantes modificações no ambiente costeiro marinho, sejam causadas por agentes naturais ou antrópicos, impõe a necessidade de se conhecer a morfodinâmica e morfografia costeira de maneira a auxiliar na conduta de utilização desse ambiente para fins de navegação, projetos de engenharia ou conservação do mesmo a partir de estudos ecológicos. A metodologia sugerida, neste trabalho, pode ser utilizada com pequenas embarcações comerciais, um GPS geodésico e um ecobatímetro, destinada a avaliar os relevos submersos de regiões costeiras rasas, principalmente costões rochosos e zonas recifais. O levantamento hidrográfico foi feito em três praias de Armação dos Búzios, a partir da associação dos valores de profundidade registrados por um ecobatímetro monofeixe associado a um rastreador geodésico, processado pelo método relativo cinemático. A técnica mostrou ser mais eficiente que o uso de correções de redução batimétrica clássicas. O trabalho também enfatiza a importância do pós-processamento dos dados para melhoramento dos modelos gerados. A partir dos mapas bidimensionais, as diferenças topográficas quanto à inclinação e profundidade puderam ser evidenciadas, enquanto que os modelos tridimensionais destacaram os afloramentos formados por recifes rochosos. Este trabalho oferece subsídios para estudos futuros de levantamentos hidrográficos de regiões costeiras rasas e caracterizase como importante ferramenta de gerenciamento costeiro. Palavras chaves: batimetria, ecobatímetro, GPS, costão rochoso, recifes rochosos Low-cost solution for correction of tidal changes in the mapping of coastal environments A B S T R A C T Constant changes in the marine coastal environment caused by natural or anthropic agents lead to the need of knowing the coastal morphodynamic and morphography in order to assist its use for navigation purposes, engineering projects, or its conservation by means of ecological studies. The methodology suggested in this study can be used with small commercial vessels with a geodesic GPS and an echo sounder and it is used to assess submerged reliefs of shallow coastal regions, mainly rocky shores, and reef zones. The hydrographic survey was carried out on three beaches of Armação dos Búzios by associating depth values registered by a single-beam echo sounder associated with a geodesic tracker, processed by the kinematic relative method. This technique was more efficient than the use of classical bathymetric reduction corrections. Our study also emphasizes the importance of post-processing of data to improve the generated models. From two-dimensional maps, topographic differences in slope and depth could be evidenced, while three-dimensional models showed outcrops formed by rocky reefs. This study offers support for future studies on hydrographic surveys of shallow coastal regions and it is an important coastal management tool.

No abstract

No abstract