Path planning of scenic spots based on improved A* algorithm.

Traditional scenic route planning only considers the shortest path, which ignores the information of scenic road conditions. As the most effective direct search method to solve the shortest path in static road network, A* algorithm can plan the optimal scenic route by comprehensively evaluating the weights of each expanded node in the gridded scenic area. However, A* algorithm has the problem of traversing more nodes and ignoring the cost of road in the route planning. In order to bring better travel experience to the travelers, the above factors are taken into account. This paper presents a path planning method based on the improved A* algorithm. Firstly, the heuristic function of the A* algorithm is weighted by exponential decay to improve the calculation efficiency of the algorithm. Secondly, in order to increase the practicality of the A* algorithm, the impact factors that road conditions is introduced to the evaluation function. Finally, the feasibility of the improved A* algorithm is verified through simulation experiments. Experimental results show that the improved A* algorithm can effectively reduce the calculation time and road cost.

Expansion and hazard risk assessment of glacial lake Jialong Co in the central Himalayas by using an unmanned surface vessel and remote sensing.

Glacial lake outburst floods (GLOFs) are a severe hazard in the Himalayas. Glacial lake expansion and the corresponding volume increase play major roles in GLOFs as well as climate change. Furthermore, mass movement and dam conditions play a major role in the GLOF initiation process. Recently, because of global warming, glacial lakes in the central Himalayas have been expanding rapidly. Owing to a lack of systematic assessment and meticulous field surveys, people living downstream are at great risk of GLOFs. Comprehensive investigations and assessment of the relationships among lake expansion, lake dam conditions, and GLOF risk are urgently needed. In this study, we surveyed Jialong Co, a typical end-moraine dammed lake in Poiqu River in the central Himalayas by using Landsat and Sentinel satellite images from the past 32 years, field work, and depth measurements using an unmanned surface vessel on August 28, 2020. The results showed that Jialong Co had experienced slow-quick-slow expansion, increasing in area from 0.13 ± 0.03 to 0.60 ± 0.02 km2. The lake bathymetric map revealed that the lake volume was (3.75 ± 0.38) × 107 m3 in 2020. Lake expansion occurred in the area from which the mother glacier retreated, indicating a close connection between the lake and its mother glacier and revealing that topography controlled the lake expansion process. Furthermore, thorough field work revealed that outlet dynamics and external water erosion are vulnerable elements in the disaster chain that initiate and affect the GLOF hazard of Jialong Co. Overall, this case study could help scholars understand the expansion mechanism of end-moraine dammed lakes and aid in hazard assessment of glacial lakes in the central Himalayas.

Characteristics and controls of vegetation and diversity changes monitored with an unmanned aerial vehicle (UAV) in the foreland of the Urumqi Glacier No. 1, Tianshan, China.

Exposed surfaces following glacial retreat are ideal field laboratories for studying primary vegetation succession. Many related studies based on ground sampling methods have been performed worldwide in proglacial zones, but studies on species diversity and vegetation succession using aerial photography have been rare. In this study, we investigated soil organic carbon (SOC), total nitrogen (TN), plant species diversity, and fractional vegetation cover (FVC) along a chronosequence within the foreland of Urumqi Glacier No. 1 by combining field sampling and aerial photography. We then analysed soil development and vegetation succession along distance (distance from glacier terminus) and time (terrain age) gradients as well as the relationships between topographic and environmental variables (aspect, slope, SOC, and TN), distance, time, and species distributions. The results indicated that: (1) plant diversity and FVC showed increasing trends with increases in distance and terrain age, whereas soil nutrient content varied nonlinearly; (2) Silene gonosperma, Leontopodium leontopodioides, and Saussurea gnaphalodes were the dominant species in the early, transient, and later succession stages, respectively. Cancrinia chrysocephala occurred in all stages and had a high abundance in the early and later stages; and (3) the relationships of FVC with soil nutrient content were nonlinear. Moreover, distance and site age played important roles in species distribution. These findings confirm that distance and terrain age positively affect vegetation succession. The increase in FVC facilitated the accumulation of soil nutrition, but this trend was affected by the rapid growth of plants. Caryophyllaceae and Asteraceae were the most common plants during the succession stages, and the former tended to colonise in the early succession stage. We conclude that the UAV-based method exhibits a high application potential for assessing vegetation dynamics in glacier forelands, which has a significance for long-term and repeated monitoring on the process of vegetation colonisation and succession in deglaciated areas.