Surface water is an essential element that supports natural ecosystem health and human life, and its losses or gains are closely related to national or local sustainable development. Monitoring the spatial-temporal changes in surface water can directly support the reporting of progress towards the sustainable development goals (SDGs) outlined by the government, especially for measuring SDG 6.6.1 indicators. In our study, we focused on Baiyangdian Lake, an important lake in North China, and explored its spatiotemporal extent changes from 2014 to 2020. Using long-term Sentinel-1 SAR images and the OTSU algorithm, our study developed an automatic water extraction framework to monitor surface water changes in Baiyangdian Lake at a 10 m resolution from 2014 to 2020 on the Google Earth Engine cloud platform. The results showed that (1) the water extraction accuracy in our study was considered good, showing high consistency with the existing dataset. In addition, it was found that the classification accuracy in spring, summer, and fall was better than that in winter. (2) From 2014 to 2020, the surface water area of Baiyangdian Lake exhibited a slowly rising trend, with an average water area of 97.03 km2. In terms of seasonal variation, the seasonal water area changed significantly. The water areas in spring and winter were larger than those in summer and fall. (3) Spatially, most of the water was distributed in the eastern part of Baiyangdian Lake, which accounted for roughly 57% of the total water area. The permanent water area, temporary water area, and non-water area covered 49.69 km2, 97.77 km2, and 171.55 km2, respectively. Our study monitored changes in the spatial extent of the surface water of Baiyangdian Lake, provides useful information for the sustainable development of the Xiong’an New Area and directly reports the status of SDG 6.6.1 indicators over time.

Abstract:With the rapid development of nautical surveying and mapping and the growing of the mobile platform products, there is a growing demand for mobile electronic nautical chart information system. Traditional desktop electronic chart information system has played an important role in the field of hydrographic surveying and mapping. But it is very inconvenient to carry it offshore for maritime staff. We have developed the mobile electronic nautical chart information system based on IOS after deeply digging the demand of maritime staff for a mobile system. It realizes some traditional functions like the desktop system such as parsing and rendering of vector nautical chart file, integrated display of various kinds of map layers, data update and sharing inside the system and so on. Besides that, it also realizes some novel functions taking advantage of the characteristics of the mobile devices, such as trajectory recording and navigation, etc. This system is on trial in the relevant operational departments and reaches the level of operational application.