## 6 Conclusions  
The green tide distribution envelope and its prediction information are essential reference information in the decision-making of green tide disaster prevention and mitigation. We carried out research on the production of the envelope of green tide using remote sensing and geographic information analysis technology, and the main conclusions are as follows. To address the issue of excessive vertices on the distributed envelope produced by buffer analysis, we proposed an envelope simplification model based on azimuth difference and side length (SM-ADSL) with a high simplification ratio and low deformation. The four-phase envelope simplification results showed that the simplification ratio was greater than 150, the algebraic error was less than 0.15%, and the overall error was less than 0.75%. Compared with the equidistance and Douglas-Peucker methods, SM-ADSL performs best in simplifying the distribution envelope, where SM-ADSL has the most minor algebraic error, while its overall error is similar to that of the Douglas-Peucker method and smaller than that of the equidistance method. Tests showed that using the simplified distribution envelope as the initial field for drift prediction significantly reduced the prediction time, thereby enhancing the efficiency of emergency decision-making for green tide disasters. When using images with different spatial resolutions to extract the green tide and produce its distribution envelopes, we found that in the initial stage, due to the small size of green tide patches, high-resolution images can detect smaller patches, while lower-resolution marine images cannot detect these small patches, leading to significant differences in the distribution envelopes. In the development and outbreak stages, the green tide patches become larger after sufficient growth and aggregation, and the differences in distribution envelopes using images with different resolutions become smaller. Therefore, we recommend to use higher-resolution satellite images to detect green tides during their occurrence. This will ensure that even small patches are identified, providing more accurate information for early warning and decision-making. The smoothness hypothesis of the distribution envelope in this paper is superior to manually delineated rigid envelopes. Smoothed envelopes enable the formation of standardized and uniform boundaries, which facilitate comparative analyses between different dates within the same year as well as comparisons of the same period across different years. Meanwhile, further research can be conducted on the mapping of envelopes, such as comprehensively considering the combined effects of green tide growth, surface wind fields, and ocean currents to form more realistic boundaries. When determining the buffer radius, the influence of shallow water depths and obstacles in nearshore areas could be taken into account, allowing for the setting of different buffer radii in different regions. Conceptualization, Y.D., G.H. and S.G.; methodology, Y.D. ; software, Y.D. ; validation, Y.D., G.H. and S.G.; formal analysis, Y.D. ; investigation, Y.D. ; resources, S.G.; data curation, Y.D. ; writing--original draft preparation, Y.D. ; writing--review and editing, G.H., Z.Y., Z.W., L.W., C.Y. and S.G.; visualization, Y.D. ; supervision, G.H. and S.G.; project administration, L.W. ; funding acquisition, L.W. and S.G. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Key Research and Development Program, China (grant no. 2022 YFC3106005), and Shandong Provincial Key Laboratory of Marine Ecology and Environment & Disaster Prevention and Mitigation, China (grant no. 202208). The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.