Possibility of the underwater topography studying of large accumulative forms according to Sentinel-2 data

The study of the marine coastal accumulative forms' relief allows clarify the regularities of their evolution. The use of satellite imagery to create bathymetric maps provides information about structure and dynamics of the underwater relief. To date, there are a number of developed algorithms for calculating the depths using satellite data with an expanded range of spectral channels (WorldView-2/3). There are also designs for using images with a standard range of channels (Red-Green-Blue-NIR). The objective of this study is to build bathymetric maps based on data from the non-commercial satellite Sentinel-2. The studied accumulative forms are located in the Black and Azov Seas. Regions characterized by increased muddiness and a small number of cloudless days. In this study the qualitative information was obtained about presence and value of the underwater part of the accumulative forms' dynamics. It has been shown that the detail of the Sentinel-2 images for this purpose is sufficient. The algorithm, chosen for mapping, is based on the use of the linear regression method of the ratio of natural logarithms of the reflected radiation values of pairs of channels. The software implementation of mapping was based on the ScanEx Image Processor software. Digital bottom relief models were obtained for two sites with depths of 0-7 m. For correct of the underwater relief at greater depths, the obtained DEMs were supplemented with data from navigation maps. Estimation of accuracy was carried out according to the bathymetric measurements made by the Shirshov Institute of Oceanology RAS. The analysis showed that Sentinel-2 images are an important source of data for scientific research in shallow water areas. However, there are limitations that do not allow creating a universal method for creating bathymetric maps.