Improved NDFI-based flood extraction method and system, terminal and application

The invention belongs to the technical field of flood information extraction, and discloses an improved NDFI-based flood extraction method and system, a terminal and application. The improved NDFI-based flood extraction method comprises the steps: carrying out preprocessing of SAR satellite data, calculating a flood index based on a preprocessed image, removing an abnormal value, calculating a threshold value and removing image elements with the gradient larger than 5 degrees and image spots with the area smaller than 0.001 km to obtain a flood inundation range A, and performing preliminary extraction on flood disaster conditions of a research area based on an NDFI method; constructing an impervious surface and a permanent water body exclusion layer based on land coverage product data and a cloud platform, extracting flood information of a non-town area through an impervious surface exclusion layer with the resolution of 30 meters, preliminarily extracting a result through a permanent water body exclusion lay