Sediment and Shallow Coastal Water Detection Utilizing MODIS Land Channels over Gulf of Martaban

Application of clear waters (Case 1) algorithm to satellite imagery acquired with Moderate Resolution Imaging Spectroradiometer (MODIS) over turbid coastal waters (Case 2) often results in negative water-leaving radiances over extended areas. Also, the maximum reflectances for ocean color channels are significantly smaller than those for the land channels at similar wavelengths. Because of that, at the bright coastal water areas, ocean color channels (0.488, 0.531 and 0.551 µm) often saturate. The saturation of these channels will contribute to the lost of geophysical and biological activities in the data. So, in order to overcome this circumstance, it is reasonable to use MODIS land and atmosphere channels (1 to 7) to derive an algorithm for the detections of turbid and shallow coastal water areas. In order to improve chlorophyll retrieving algorithm over the ocean, an algorithm to mask out the turbid coastal water area needs to be developed. In this paper, a simple algorithm to identify and mask shallow coastal water and high amounts of suspended sediment area in the Gulf of Martaban using MODIS L1B image is suggested and demonstrated. This algorithm uses log10 ratio of two MODIS solar channels originally designed for remote sensing over land and cloud properties centered at 0.47 and 0.55 µm (bands 3 and 4 respectively). Shallow coastal water and the area with high amount of suspended sediment detected by our algorithm were then masked. The result of this algorithm was then evaluated by comparing each masked area with the corresponding mask generated by using other established technique.