Comparação de dois métodos geofísicos acústicos no mapeamento de fundos submersos: estudo de caso no Mar de Cananéia, Sistema estuarino de Cananéia-Iguape (SP)

• Autor(a) principal: Silva, Cristiane Ferreira da
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/13864
• topic: Side scar sonar; RoxAnn; Cananéia; Sonar de varredura lateral; RoxAnn; Cananéia; CNPQ::CIENCIAS EXATAS E DA TERRA::OCEANOGRAFIA

Estuaries are highly dynamic environments which concentrate the largest part of the world`s population in it`s surroundings. They are complex environments which need a variety of studies. The objective of this work is to contribute to a better understanding of the estuarine system, having as a main objective the comparison between two geophysical acoustic methods in the mapping of a submersed portion of the Cananéia Sea, located in the Estuarine System of Cananéia Iguape (SP). The equipment used in this research were the Side Scan Sonar and the RoxAnn Acoustic Ground Discrimination System, through the correlation of the geological bottom samples. The comparison of the acoustic pattern between the Side Scan Sonar and the geological bottom samples enabled the recognition of 6 distinct acoustic patterns and the positive correlation between the medium diameters of the sediments was 50%. The correlation of the acoustic feedback of the RoxAnn Acoustic Ground Discrimination System and the medium diameter of the sediments was equally 50%. This is due to the fact that the data produced by the echo 1 and echo 2 of this system show that because it is a single beam and because it analyses acoustic intensity feedback data, the equipment may also respond to other environmental factors which are not only related to the medium diameter of sediments. When comparing the acoustic feedback taken from the Side Scan Sonar and the RoxAnn Acoustic Ground Discrimination System a positive result of 93% was obtained. This may be explained due to the fact that the Side Scan Sonar generates an acoustic ground image. In areas where one has high value samples from echo 1 and echo 2 and also from the RoxAnn Acoustic Ground Discrimination System, one may correlate to these places the influence of fine sediment compression through the analysis of the images taken from the Side Scan Sonar. By comparing these two methods it was possible to establish an interval of values for echo 1 which can be associated to the medium diameter of the sediments. In this way, values between 0,170 to 0.484 milivolts can be associated to fine sediments with granulometry variating up to very fine sediments. Values between 0.364 to 0.733 can be associated to fine sediments with granulometry variating from medium to fine sediments. Values above 0.805 milivolts to 1.585 milivolts can be associated to coarser sediments such as biodetritic carbonates or thick sediments. Finally, values above 2.790 milivolts can be associated to rocky emergences.