A hyperspectral view of the North Sea

On the 16th of June 2003 a CASI hyperspectral airborne remote sensing campaign took place above the Southern North Sea, just offshore of Oostende. In coincidence with the airborne overpasses seaborne measurements of water leaving reflectance and water quality parameters were performed. In addition nearsimultaneous satellite imagery are available. This paper describes the analysis of the airborne data. The CASI data have been atmospherically corrected using the software WATCOR which is based on the radiative transfer code MODTRAN and takes into account atmospheric and air/water interface effects. Two different approaches for atmospheric information retrieval were tested. In the first approach aerosol information and visibility are estimated from sun photometer measurements combined with MODTRAN radiative transfer simulations. The second method is based on an adapted dark-target approach to estimate the visibility. The results of both methodologies are comparable. The data are subsequently geometrically corrected with PARGE. A semi-analytical approach is used to retrieve the concentration of the water constituents: for chlorophyll determination a bio-optically modeled red/NIR band ratio algorithm is applied to the data; to quantify the Suspended Particulate Matter a single band NIR algorithm is used. The results of these semi-analytical methods were compared to an analytical approach where the water quality parameters are retrieved using a matrix inversion of the Gordon reflectance model