Quantification of the total suspended matter concentration in the sea breaking zone from in situ measurements and remotely sensed data - two empirical approaches

Abstract

Remote sensing techniques can be used to calculate suspended sediment concentrations and to understand the flux and distribution of sediments driven by mechanisms such as tides and waves, river discharges, etc. The main objective of this study is the quantification of the Total Suspended Matter (TSM) concentration in the sea breaking zone for a particular area of the Portuguese coast, around Aveiro. The methodology used was based on in situ measurements and multi spectral satellite images. In situ experimental techniques (maritime platform, aerial platform, simulation on the beach and water sample collection in the breaking zone) were used to determine a relationship between the TSM concentration and the seawater reflectance in the breaking zone. Spectral reflectance was measured with a spectroradiometer and water samples were simultaneously collected. Empirical relationships were established between TSM concentration and the equivalent reflectance values for sensors SPOT/HRVIR, TERRA/ASTER and Landsat/TM at visible and Near Infra Red (NIR) bands computed from the experimental data. Satellite images from ASTER, SPOT HRVIR and Landsat TM were used together with the same empirical models. These satellite images were calibrated and atmospherically corrected. Equations of linear, polynomial, logarithmic, power and exponential models were tested for the satellite image bands on the visible and near infrared. The coefficients of determination (R-2) were also calculated for each model. The results obtained from the two approaches, in situ measurements and directly from the multi spectral satellite images, were analysed.