Method for determining the time of opening and freezing of the river by protected multispectral satellite data and measurements by the MODIS instrument

An observation of surface waters is of a great importance for environmental, hydrological research, as well as practical applications and for the Russian Ministry of Emergency Situations. This article deals with the issue of detection and monitoring of surface waters using optical remote sensing by the MODIS multispectral satellite instrument. The current status and problems in this area are briefly discussed. The water detection is based on an analysis of NDVI vegetation index values calculated from measurements throughout the year from a clear division by value of plant, snow or water index values. Based on this, a spatio-temporal mask of water objects or a mask is built, the pixels of which are only used to analyze the values of the vegetation index. Next, the graphs of spatiotemporal dynamics of water mask pixels and construct smoothed values are considered. The following step is related to the search in these dependencies for the moment of opening of the river from winter ice and freezing of the river. A description is given of the processing of real measurements for the territory of the Ob-Tom interfluve, in the region of the city of Tomsk.