Lake bottom topography is a basic parameter that reflects the elevation of all lake bottom geographical locations. In this study, a novel method was proposed for mapping lake bottom topography by combining the water occurrence map from the Global Surface Water (GSW) dataset with long-term measured water levels. This method took advantage of the following feature: the rapid change in water level of a lake’s dynamic inundation area leads to a different water occurrence frequency and, therefore, put forward the concept of lake water level frequency, which refers to the frequency at which the water level is higher than or equal to a specified elevation. As water occurs more frequently in lake bottoms with lower elevations and less frequently in lake bottoms with higher elevations, we assume that lake water level frequency is identical to the water occurrence frequency over a long time. The water level frequency curve of all the measured water level data was generated through the P-III distribution function, and the elevation values from the water level frequency curve were assigned to pixels with the same frequency in the water occurrence map in order to generate the lake bottom topographic map. A case study was conducted on Poyang Lake in China to demonstrate the performance of the method. The derived bottom topographic map of Poyang Lake was verified by four measured sections. The results showed that the proposed method was feasible and could well reflect the bottom topography of Poyang Lake. The absolute error was mostly less than 0.5 m, the mean relative error was 7.4%, and the root mean square error was 0.99 m. The proposed method enriches the mapping means of lake bottom topography and has the potential to become a useful tool with a broad application prospect.

Monitoring cable sheath current is crucial for guaranteeing the secure and efficient operation of high-voltage cable tunnels. In this study, a three-dimensional (3D) panoramic digital model of a tunnel in Beijing is modeled, a parallel cable sheath current simulation model is proposed, and a 3D panoramic visualization system with which the cable sheath current can be simulated online is developed in order to generate early warnings on the sheath current situation. The accuracy of the simulation model is verified and the results are as follows: The difference between the simulated sheath current and the actual measurement is within a maximum margin of 3.71%. A phase sequence optimization strategy can be obtained after calculations based on the simulation model, and an average sheath current reduction of 47.2% can be achieved following the optimization strategy. This study introduces a new approach by which cable sheath current dynamics and real-time warning against anomalies are visualized on a 3D tunnel model. In addition, a sheath current simulation model is integrated in the 3D visualization system developed in this study, and phase sequence optimization strategies for cables with abnormal sheath currents are automatically suggested, which may provide scientific support for auxiliary decision-making in real-time cable operation.