This article proposed a PairCon-simultaneous localization and mapping algorithm to construct dense maps of large-scale scenarios in real time, which is operated in an integral platform containing two personal computers (PCs). This platform can operate the mapping thread independently in a PC to guarantee sufficient memory resources. In this context, the synchronous visualization of 3-D maps can be achieved in such a platform. In contrast, traditional algorithms are limited by the short operation distance, under the requirement of simultaneous data collection and 3-D maps construction in a PC. In addition, the memory resource provided by a single PC is limited, which restricts the constructing scale of maps. Thus, we use a separate PC to construct maps independently to relieve the distance constraint and exploit the socket method to conduct the transmission of data with the point cloud. Meanwhile, we introduce the ReBlur algorithm into the semi-direct method to reduce the error accumulation of the odometer in the tracking thread, which improves the robustness performance. In addition, the method combining the memory management and DBow2 algorithm is adopted to improve the accuracy of loop detection. In the considered system, the quality of maps and the performance of the odometer are evaluated by ICL-NUIM and the datasets, such as TUM, DIODE, and so on, respectively. Finally, under the simulation environment of AirSim and Gazebo, we construct maps based on the image data of other scenarios, which is used to show the quality of the construction.

Coastal erosion is widespread under conditions of changing hydrodynamics and diminishing sediment supply, and exposure assessment to erosion hazard has received increasing attention. In this study, we explore the impact of spatial heterogeneity of land use within administrative units on exposure assessment of land use value to erosional hazard. We illustrate land use diversity using the Shannon’s diversity index (SHDI) and consider the distance effect by comparing five different buffer zones according to the distance to the coast (i.e., 0–1 km, 0–2 km, 0–3 km, 0–4 km, 0–5 km). Our results show that coastline change and socio-economic development are responsible for land use heterogeneity within the administrative units. Using a buffer zone of 1-km along the coast as the assessment unit leads to an increase in the number of townships that have high and very high exposure of land use value when compared with the assessment result that is based on the whole township area. Furthermore, the 1-km buffer zone can be divided into subunits if very high SHDI values exist within the administrative boundary. This study demonstrates that heterogeneity in land use identified at a fine spatial scale should be given full consideration in carrying out exposure assessment to hazards in a dynamic deltaic coast.

Storm waves and rising sea levels pose significant threats to low-lying coastal areas, particularly sandy beaches, which are especially vulnerable. The research on the long-time-scale changes in sandy coasts, especially the identification of tipping points in the shoreline-retreat rate, is limited. Vung Tau beach, characterized by its low terrain and rapid tourism-driven economic growth, was selected as a typical study area to quantify the shoreline retreat throughout the 21st century under various sea-level rise (SLR) scenarios, and to identify the existence of tipping points by investigating the projected annual change in shoreline retreat (m/yr). This study employs the Probabilistic Coastline Recession (PCR) model, a physics-based tool specifically designed for long-term coastline change assessments. The results indicate that shoreline retreat accelerates over time, particularly after a tipping point is reached around 2050 in the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios. Under the SSP5-8.5 scenario, the median retreat distance is projected to increase from 19 m in 2050 to 89 m by 2100, nearly a fourfold rise. In comparison, the retreat distances are smaller under the SSP1-2.6 and SSP2-4.5 scenarios, but the same accelerating trend is observed beyond 2050. These findings highlight the growing risks associated with sea-level rise, especially the rapid increase in exceedance probabilities for retreat distances by the end of the century. By 2100, the probability of losing the entire beach at Vung Tau is projected to be 22% under SSP5-8.5. The approach of identifying tipping points based on the PCR model presented here can be applied to other sandy coastal regions, providing critical references for timely planning and the implementation of adaptation measures.