Imagery-derived bathymetry in Strait of Johor's turbid waters using multispectral images

Abstract

Although vessel-based acoustic sounding technique is accurate, however it is typically constrained by high operating costs, logistic difficulties and limited spatial coverage. It seems it is necessary to employ an alternative approach that can reduce the aforementioned high operation cost. The development of the imagery-derived bathymetry has brought in the new revolution in hydrography. The paper highlights the application of incorporating satellite remote sensing techniques to extract bathymetry information from the freely downloadable Landsat-8 satellite images. In this study, two different band ratio transform empirical models have been utilised to transform the reflected radiances of green and blue bands into bathymetry depths at the coastal region adjacent to Tanjung Kupang, Strait of Johor, Malaysia. The inland swampy area is vegetated by lavish mangroves while the shoreface is fronted by flat slopes with turbid suspended sediment. In the course of experiment, the results from Stumpf et al.'s model and Dierssen et al.'s model show a reasonable agreement, with similar correlation coefficient (r) of 0.76 between the imagery-derived depths and in-situ bathymetry depths from vessel-based sounding. The Stumpf et al.'s model has achieved root mean square error (RMSE) of 0.885 metres and mean absolute error (MAE) of 0.631 metres; while Dierssen et al.'s model delivers RMSE of 0.878 metres and MAE of 0.629 metres respectively. Although these two algorithms are slightly different, however the end results produced are quite close in this study. The results show that both empirical models represent a promising outcome and can be used to complement data from vessel-based single beam sounding, which is normally obtained at medium to course profiling resolution for the purpose of survey reconnaissance and survey planning.